EP4162234A1

EP4162234A1 - Improving determination of target location

Info

Publication number: EP4162234A1
Application number: EP21820926.0A
Authority: EP
Inventors: Rafi ZALTZMAN
Original assignee: Israel Aerospace Industries Ltd
Current assignee: Israel Aerospace Industries Ltd
Priority date: 2020-06-07
Filing date: 2021-05-25
Publication date: 2023-04-12
Also published as: IL275201B; IL275201A; EP4162234A4; WO2021250651A1

Abstract

A method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV) comprises: (a) receiving, from the system, measurement data, associated with calibration mission(s), and indicative of measurements recorded, by UAV sensor(s), at a first plurality of points. This data is indicative of coordinates of known-location target(s) (measured position information), (b) receiving known coordinates of these target(s) (known position information), (c) deriving correction data associated with each point, by comparing the measured and known position information. This enables correction of second measurement data associated with the sensor(s) and with a UAV target-location mission, in a situation of fixed sensor inaccuracies. This mission is associated with determining location information of other target(s). This data is indicative of measurements recorded by the sensor(s) at a second plurality of points. For corresponding points in the first and second pluralities of points, sensor orientations meet a first similarity criteria.

Description

IMPROVING DETERMINATION OF TARGET LOCATION

TECHNICAL FIELD

The presently disclosed subject matter relates to locating targets.

BACKGROUND Vehicles such as Unmanned Aerial Vehicles (UAVs) are used to identify and locate various targets, such as objects. In some cases, there are errors and inaccuracies associated with various sensors used in the location process. These errors can cause errors in the calculated location of a target, compared to its true location.

GENERAL DESCRIPTION According to a first aspect of the presently disclosed subject matter there is presented a method of performing calibration of a target-positioning system (target coordinates) with Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by sensors of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates at least one known- location target, the coordinates constituting first measured position information; b) receiving known coordinates at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and in the second plurality of points, orientations of the at least one sensor, meet a first similarity criterion.

In addition to the above features, the method according to this aspect of the presently disclosed subject matter can include one or more of features (i) to (xxxviii) listed below, in any desired combination or permutation which is technically possible:

(i) wherein the orientations of the at least one sensor comprise orientations relative to at least one coordinate axis of the earth.

(ii) the orientations of the at least one sensor comprise orientations relative to at least one coordinate axis of the UAV.

(iii) the correction of the second measurement data utilizes at least one of interpolation and extrapolation of the correction data.

(iv) the correction data correspond to one or more coordinate axes of the at least one known-location target.

(v) the first similarity criterion comprises first orientations of the at least one sensor, associated with the first plurality of points, corresponding to second orientations of the at least one sensor, associated with the second plurality of points.

(vi) the at least one calibration mission associated with a first path of flight, where the target-location mission is associated with a second path of flight, and where the first path of flight corresponds to the second path of flight. (vii) the first path of flight comprises movement at a plurality of distances from the at least one known-location target.

(viii) the first path of flight comprises movement at a plurality of distances from the at least one known-location target.

(ix) the first path of flight comprises flight over the at least one known- location target.

(x) the first path of flight comprises flight at a plurality of altitudes.

(xi) the fixed sensor inaccuracies comprise sensor inaccuracies associated with installation of the at least one sensor in the UAV.

(xii) the fixed sensor inaccuracies comprise sensor inaccuracies associated with boresight error.

(xiii) the fixed sensor inaccuracies are associated with at least one of an imaging device, a range finder, an Inertial Navigation System and a compass.

(xiv) the imaging device comprising at least one of an electro-optical (EO) device and an infra-red (IR) device.

(xv) the method further comprising: d) storing the correction data.

(xvi) the method further comprising: e) receiving, from the target-positioning system, the second measurement data, the second measurement data is indicative of coordinates of the at least one other target, the coordinates constituting second measured position information.

(xvii) The method further comprising: f) determining, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and g) adjusting the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

(xviii) the method further comprising: h) determining, based at least on the corrected second measurement data, the location information of the at least one other target.

(xix) the determination of the location information of the at least one other target is based at least on the second measured position information.

(xx) at least one of the steps (e), (f) and (g) is performed in real time, utilizing stored correction data.

(xxi) at least one of the steps (e), (f) and (g) is performed in the UAV.

(xxii) at least one of the steps (e), (f) and (g) is performed by a ground system. (xxiii) the method further comprising: i) outputting the location information of the at least one other target to at least one external system.

(xxiv) the location information of the at least one other target is output together with an image of the target. (xxv) for corresponding points in the first plurality of points and second plurality of points, relative positions, of the UAV and of a corresponding target, meet a second similarity criterion.

(xxvi) the second similarity criterion comprises first relative positions of the UAV and of the at least one known-location target, associated with the first plurality of points, corresponding to second relative positions of the

UAV and of the at least one other target, associated with the second plurality of points. (xxvii) one or more coordinate axes of the at least one known-location target comprise at least one of a longitude, a latitude and an altitude.

(xxviii)the at least one calibration mission precedes the target-location mission.

(xxix) the at least one calibration mission follows the target-location mission. (xxx) the at least one known-location target comprises a fixed-location target.

(xxxi) the fixed-location target comprises one of a ground structure, a tree, a road junction, and a street junction.

(xxxii) the ground structure is one of a building and a tower.

(xxxiii)the first measured position information is associated with the base of the ground structure.

(xxxiv)the known coordinates of the at least one known-location target are known to within a defined accuracy.

(xxxv) The method further comprising: j) adjusting the second measured position information utilizing the correction data, thereby deriving corrected second measured position information associated with at least one second point of the second plurality of points.

(xxxvi)The method further comprising: k) outputting the corrected second measured position information to at least one external system. (xxxvii) The method further comprising: l) determining the location information of the at least one other target, based on the corrected second measured position.

(xxxviii) the first measured position information is indicative of one or more known first orientation angles of the at least one known-location target in one or more orientation directions, wherein the second measured position information is indicative of one or more second orientation angles of the other target in one or more orientation directions.

According to a second aspect of the presently disclosed subject matter there is presented a system configured to perform calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the system comprising a processing circuitry configured to: a) receive, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known- location target, the coordinates constituting first measured position information, b) receive known coordinates of the at least one known-location target, constituting known position information; and c) derive correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and in the second plurality of points, orientations of the at least one sensor, meet a first similarity criterion. This aspect of the disclosed subject matter can optionally include one or more of features (i) to (xxxix) listed above, mutatis mutandis , in any desired combination or permutation which is technically possible.

In addition to the above features, the method according to this aspect of the presently disclosed subject matter can optionally include one or more of features (xl) to (xliv) listed below, in any desired combination or permutation which is technically possible.

(xxxix)the processing circuitry further configured to: d) receive, from the target-positioning system, the second measurement data, the second measurement data is indicative of coordinates of the at least one other target, the coordinates constituting second measured position information.

(xl) the processing circuitry is further configured to: e) determine, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and f) adjust the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

(xli) the processing circuitry further configured to: g) determining, based at least on the corrected second measurement data, the location information of the at least one other target.

(xlii) the target-positioning calibration system is comprised in the UAV.

(xliii) the target-positioning calibration system is comprised in a ground station. (xliv) the UAV, comprising the system according to the first aspect of the presently disclosed subject matter, and according to any one of features (i) to (xliv). According to a third aspect of the presently disclosed subject matter there is presented a non-transitory computer readable storage medium tangibly embodying a program of instructions that, when executed by a computer, cause the computer to perform a method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising:: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known- location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and in the second plurality of points, orientations of the at least one sensor, meet a first similarity criterion. This aspect of the disclosed subject matter can optionally include one or more of features (i) to (xxxix) listed above, mutatis mutandis , in any desired combination or permutation which is technically possible.

According to a fourth aspect of the presently disclosed subject matter there is presented a method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known- location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, d) receiving, from the target-positioning system, second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and second plurality of points, orientations of the at least one sensor, meet a first similarity criterion, wherein the second measurement data is indicative of coordinates of the at least one other target, the coordinates constituting second measured position information; e) determining, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and f) adjusting the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

In addition to the above features, the method according to this aspect of the presently disclosed subject matter can optionally include the feature listed below:

(xlv) The method further comprising: g) determining, based at least on the corrected second measurement data and on the second measured position information, the location information of the at least one other target.

According to a fifth aspect of the presently disclosed subject matter there is presented a method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known- location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information; d) receiving, from the target-positioning system, second measurement data, the second measurement data is indicative of coordinates of the at least one other target, the coordinates constituting second measured position information, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and second plurality of points, orientations of the at least one sensor, meet a first similarity criterion; e) determining, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and f) adjusting the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

According to a sixth aspect of the presently disclosed subject matter there is presented a method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known-location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information; d) receiving, from the target-positioning system, second measurement data, the second measurement data is indicative of coordinates of the at least one other target, the coordinates constituting second measured position information, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and second plurality of points, orientations of the at least one sensor, meet a first similarity criterion; and e) adjusting the second measured position information utilizing the correction data, thereby deriving corrected second measured position information associated with at least one second point of the second plurality of points.

According to a seventh aspect of the presently disclosed subject matter there is presented a method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data is indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known-location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and second plurality of points, relative positions, of the sensor(s) and of a corresponding target, meet a second similarity criterion.

According to an eighth aspect of the presently disclosed subject matter there is presented a method of performing calibration of a target-positioning system of a vehicle, the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the vehicle, the first measurement data v indicative of measurements recorded, by at least one sensor of the vehicle, at a first plurality of points, the first measurement data is indicative of coordinates of at least one known-location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the vehicle, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and second plurality of points, orientations of the at least one sensor, meet a first similarity criterion.

In addition to the above features, the method according to this aspect of the presently disclosed subject matter can include one or more of features (i) to (xl) listed below, in any desired combination or permutation which is technically possible:

(xlvi) where the vehicle is an aircraft, wherein the calibration mission is a calibration flight mission, wherein the first path of travel is a first flight path, wherein the target-location mission is a target-location flight mission, wherein the second path of travel is a second flight path.

(xlvii) where the first flight path comprises flight over the at least one known- location target.

(xlviii) where the first flight path comprises flight at a plurality of altitudes.

The fourth to eighth aspects of the disclosed subject matter can optionally include one or more of features (i) to (xxxix) listed above, mutatis mutandis , in any desired combination or permutation which is technically possible.

According to another aspect of the presently disclosed subject matter there is provided a non-transitory program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform the method of any one of the fourth to eighth aspects of the disclosed subject matter.

According to another aspect of the presently disclosed subject matter there is provided a system configured to perform calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the system comprising a processing circuitry configured to perform the method of any one of the fourth to eighth aspects of the disclosed subject matter.

The methods, computerized methods, and the non-transitory computer readable storage media, disclosed herein according to various aspects, can optionally further comprise one or more of features (i) to (xlviii) listed above, mutatis mutandis , in any technically possible combination or permutation.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it can be carried out in practice, embodiments will be described, by way of non-limiting examples, with reference to the accompanying drawings, in which:

Fig. 1 illustrates schematically an example generalized view of locating a target, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 2 schematically illustrates an example generalized view of locating a target, in accordance with some embodiments of the presently disclosed subject matter; Fig. 3 schematically illustrates an example generalized view of locating a target, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 4A schematically illustrates an exemplary generalized view of axes, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 4B schematically illustrates an exemplary generalized view of fixed sensor errors, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 5A schematically illustrates an exemplary generalized view of a calibration mission, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 5B schematically illustrates an exemplary generalized view of a calibration mission, in accordance with some embodiments of the presently disclosed subject matter; Fig. 6 schematically illustrates an example generalized view of a target-location mission, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 7 illustrates an example generalized schematic diagram of a calibrated target-locating system, in accordance with some embodiments of the presently disclosed subject matter;

Fig. 8 illustrates an example generalized schematic diagram of a target-locating calibration system, in accordance with some embodiments of the presently disclosed subject matter; and Figs. 9A and 9B illustrate a generalized exemplary flow chart diagram, of the flow of a process or method, for calibration of a target-positioning system, in accordance with certain embodiments of the presently disclosed subject matter.

DETAILED DESCRIPTION

In the drawings and descriptions set forth, identical reference numerals indicate those components that are common to different embodiments or configurations.

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the presently disclosed subject matter.

It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.

It will also be understood that the system according to the invention may be, at least partly, implemented on a suitably programmed computer. Likewise, the invention contemplates a computer program being readable by a computer for executing the method of the invention. The invention further contemplates a non-transitory computer- readable memory tangibly embodying a program of instructions executable by the computer for executing the method of the invention.

Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "receiving", " deriving", "enabling", “determining”, "adjusting", "storing" or the like, refer to the action(s) and/or process(es) of a computer that manipulate and/or transform data into other data, said data represented as physical, e.g. such as electronic or mechanical quantities, and/or said data representing the physical objects. The term “computer” should be expansively construed to cover any kind of hardware-based electronic device with data processing capabilities including a personal computer, a server, a computing system, a communication device, a processor or processing unit (e.g. digital signal processor (DSP), a microcontroller, a microprocessor, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.), and any other electronic computing device, including, by way of non-limiting example, systems710and 720, and processing circuitry 820, disclosed in the present application.

The operations in accordance with the teachings herein may be performed by a computer specially constructed for the desired purposes, or by a general-purpose computer specially configured for the desired purpose by a computer program stored in a non-transitory computer-readable storage medium. Embodiments of the presently disclosed subject matter are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the presently disclosed subject matter as described herein.

The terms "non-transitory memory" and “non-transitory storage medium” used herein should be expansively construed to cover any volatile or non-volatile computer memory suitable to the presently disclosed subject matter.

As used herein, the phrase "for example," "such as", "for instance" and variants thereof describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to "one case", "some cases", "other cases", "one example", "some examples", "other examples", or variants thereof, means that a particular described method, procedure, component, structure, feature or characteristic described in connection with the embodiment s) is included in at least one embodiment of the presently disclosed subject matter, but not necessarily in all embodiments. The appearance of the same term does not necessarily refer to the same embodiment(s) or example(s).

Usage of conditional language, such as “may”, “might”, or variants thereof, should be construed as conveying that one or more examples of the subject matter may include, while one or more other examples of the subject matter may not necessarily include, certain methods, procedures, components and features. Thus such conditional language is not generally intended to imply that a particular described method, procedure, component or circuit is necessarily included in all examples of the subject matter. Moreover, the usage of non-conditional language does not necessarily imply that a particular described method, procedure, component or circuit is necessarily included in all examples of the subject matter.

It is appreciated that certain embodiments, methods, procedures, components or features of the presently disclosed subject matter, which are, for clarity, described in the context of separate embodiments or examples, may also be provided in combination in a single embodiment or examples. Conversely, various embodiments, methods, procedures, components or features of the presently disclosed subject matter, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

It should also be noted that each of the figures herein, and the text discussion of each figure, describe one aspect of the presently disclosed subject matter in an informative manner only, by way of non-limiting example, for clarity of explanation only. It will be understood that that the teachings of the presently disclosed subject matter are not bound by what is described with reference to any of the figures or described in other documents referenced in this application.

Bearing this in mind, attention is drawn to Fig. 1, schematically illustrating an example generalized view of locating a target, in accordance with some embodiments of the presently disclosed subject matter. In some examples, targets are located as disclosed with reference to target-location mission 100.

An aircraft 110, e.g. an Unmanned Aerial Vehicle (UAV) 110, is shown, from a side view, flying in a target area (not shown) that includes one or more targets 150. In the example, target 150 is located on the surface 145 of the Earth, e.g. on the ground 145. The UAV 110 utilizes in some examples various sensors, e.g. as disclosed with reference to Figs. 4B and 7, to acquire, identify, and/or determine the location of an object or other target 150. The sensors in some cases record measurements at a plurality of points along the mission path of travel or flight. That is, a goal of target-location mission 100 is to determine location information of the target 150. In some examples, target 150 is an object, e.g. a building or a vehicle. In some examples, target 150 is not an object, e.g. a feature of the ground terrain. In some examples, target-location mission is referred to herein also as a target-acquisition mission. In some examples, target- location mission is referred to herein also as a planned target-location mission - e.g. when there is a plan to perform a particular target-location mission with a particular UAV 110 to locate particular target(s) 150 by traveling a particular path of travel.

In some examples, these recorded measurements are referred to herein also as second measurements, and these plurality of points are referred to as a second plurality of points. In some examples, such a mission can provide measurement data that is indicative of coordinates in one or more coordinate axes of target 150. In some examples these coordinates are referred to herein also as second measured position information. In some examples this measurement data is referred to herein also as second measurement data.

In some examples, the target-location mission 100 is associated with determining location information of one or more other targets 150, wherein the second measurement data is indicative of second measurements recorded, by the sensor(s), at a second plurality of points.

As will be disclosed further herein, target 150 is in some examples also referred to as an "other target" 150. Xt, Yt and/or Zt refer to the actual or true position(s) of object(s) or other target(s) 150 (where "t" refers to "target"). Xt, Yt, Zt refer to the non-limiting example of determining the target location, referred to in some examples as target coordinates, in terms of three coordinate axes of the Earth, e.g. longitude, latitude and altitude. The calculated location of target 150, based on the sensor measurements, is in some examples Xm, Ym and/or Zm (where "m" indicates "measured"). Xm, Ym and/or Zm exemplify determined location information of the target. Note that location of 150 may be expressed in various units, in various reference frames and coordinate systems. Non limiting examples include degrees of Longitude and Latitude, Universal Transverse Mercator (UTM) coordinate system etc. As will be disclosed further herein with reference to Fig. 4B, in some examples there are fixed sensor inaccuracies associated with at least some of these sensors. Thus the calculated values, e.g. Xm, Ym and/or Zm, may differ from the true values, e.g. Xt, Yt and/or Zt. Thus there is a certain error in the calculated result. Such errors in the location are in some cases particularly problematic. For example, if target 150 is located in the desert, or in a large body of water such as a sea or ocean, there may in some cases be no other features 160 in the target area (buildings etc.) which can serve as anchoring points, or as reference points, that can be used to help determine the target's location. In such a case, the situation may be such that there are no other means to determine the target coordinates, and there may be greater reliance on the measurements of the sensor(s) to provide an accurate location of the target. In the figure, the lack of such features 160 is indicated by it being a dashed line.

In Figs. 5A to 9B, as described below, there are disclosed use situations, systems, and process flows, for a method of performing calibration of a target- positioning system of an UAV, which includes at least: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with one or more calibration missions performed by the UAV (or another vehicle). The first measurement data is indicative of measurements recorded, by one or more sensors of the UAV, at a first plurality of points. The first measurement data is indicative of coordinates of at least one known-location target. These coordinates are referred to herein also as first measured position information; b) receiving known coordinates of one or more known-location targets. These coordinates are referred to herein also as known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information.

In some examples, as will be shown, this enables enabling correction of second measurement data associated with the sensor(s) and with a target-location mission(s) associated with the UAV, in a situation of fixed sensor inaccuracies, in a case where, for corresponding points in the first plurality of points and second plurality of points, orientations of the at least one sensor, meet one or more first similarity criteria. In some examples this enables determination of a more accurate location of the target 150, than can be derived from the uncorrected second measurement data.

Further details of such methods are disclosed, for example, with reference to

Figs. 4B, 5, 6, 9A and 9B

Reverting now to Fig. 1, some techniques and considerations in locating targets are presented, as a basis for understanding the role of sensor errors. UAV 110 flies over the target area, at an angle of elevation E to an imaginary horizontal line 117 that is parallel to the horizon/sea level 140. In some examples, angle E can be determined based on a sensor (not shown in the figure) such as Inertial Navigation System (INS), which measures vehicle orientation relative to e.g. one or more coordinate axes of the Earth.

In some examples, UAV 110 has a sensor (not shown in this figure) for acquiring the target 150 - for example, an imaging device and/or a range finder. Examples of imaging devices are Electro-Optical (EO) and Infra-Red (IR) imaging devices, e.g. cameras. In some examples, this sensor is referred to herein also as a target-acquisition sensor, a target-locating sensor, or a locating sensor. The vector 170, of the sensor's line of sight to the target 150, has an angle A with respect to the UAV. In the figure, angle A is the non-limiting example of a depression angle of the sensor with respect to the UAV. The length of vector 170 is shown as 175. In some examples, the point where the vector 170 intersects with the ground 145 is considered the target 150, and the coordinate of such a point is considered the target location/coordinates. In other examples, any calculation based on this intersection point is considered the target location/coordinates. Note that vector 170 is in some examples based on all of the angles and range measured by the various sensors.

A target-positioning system associated with UAV 110 in some examples determines the altitude of the UAV. In some examples this UAV Altitude (ASL) Above Sea Level is denoted as h_u. This is shown in the figure as 115, Zv. (The target positioning system is not shown in this figure, but is disclosed with reference to Fig. 7). For example, the UAV could include an altimeter, which can measure barometric altitude. In another example, the UAV uses a Global Navigation Satellite System (GNSS), e.g. Global Positioning System (GPS), to determine its altitude 115.

The Target-Positioning System in some examples also knows the Target Altitude (ASL) Above Sea Level 140, denoted as h_r. This is shown in the figure as 155, Zm. For example, the target-positioning system can have access to an altitude map utilizing e.g. a Digital Terrain Model (DTM), or Digital Terrain Elevation Data (DTED). Such an altitude map provides the ASL for points on the Earth's surface. In some examples the altitude map is stored in, or is otherwise associated with, the target- positioning system. Subtracting 155 from 115 gives the height 180 of the UAV relative to target 150.

In some examples, the UAV knows its location or position, e.g. in terms of longitude-latitude ("Long-Lat") coordinates Xv, Yv (where "v" refers to "vehicle", e.g. the UAV), e.g. using Radio Frequency (RF) 195 from a ground station 190. In one example, the ground station 190 uses RF to determine range and direction to the UAV 110, and the UAV coordinates are determined based thereon. Using, for example, known per se techniques, the target-positioning system can usel80, 175 and angle A to determine the horizontal distance 185 between the UAV and the target 150. In some examples, the calculation utilizes vector length 175 and angle A. Using for example Xv, Yv, longitude-latitude coordinates Xm,Ym can be determined. Note that there exist various known per se methods of determining Xm, Ym, and/or Zm, based on sensor measurements, and that the method used in some examples depends on whether a range finder is used. Attention is now drawn to Fig. 2, schematically illustrating an example generalized view of locating a target, in accordance with some embodiments of the presently disclosed subject matter. View 200 of the UAV 110 and the target/object 150 is an aerial view of mission 100, looking at the longitude and latitude only, contrasted with the side view of Fig. 1 which also shows altitude. It is shown in this figure that the heading direction 210 of UAV 110 has, for example, a bearing angle B from North. This can be determined using, for example, a compass and/or INS.

The vector 170 from the target-locating sensor(s) associated with the UAV to target 150 has an angle C relative to the North, which can be a function of heading angle B together with the bearing angle (not shown) of the locating sensor relative to the UAV 110 bearing. In some examples this vector 170 angle is in addition to angle A disclosed with reference to Fig. 1.

Note that in some examples declinations from True North (Geodetic North) and/or Magnetic North are determined. Attention is now drawn to Fig. 3, schematically illustrating an example generalized view of locating a target, in accordance with some embodiments of the presently disclosed subject matter.

In a typical target location mission 300, the UAV travels (flies) along a path of travel 310 in the area of the target 150. In some examples, this path 310 is referred to herein also as a second path of travel, a second path of motion, or a second flight path. Note that the sensors record measurements at a plurality of the second points along path 310. In the example of the figure, three typical points 315, 320, 330 of this plurality are shown. Note that the corresponding measurements recorded at each such point are not necessarily the same, and that they may be a function of the position and attitude of the UAV and of the sensors at each point. For example, the angle A varies from point to point, in that the three exemplary angles Al, A2 and A3 associated with the three points 315, 320, 330 are of different values. At least as a result of such differences, the three corresponding line of sight vectors 170 A, 170B, 170C differ, as do their corresponding distances 175A, 175B, 175C. The behavior of the various sensors and their errors may vary as well, from point to point in path 310, as will be disclosed further herein with reference to Fig, 4B- e.g. due to errors in optical alignment. At least because of these differences, and because of the varying behavior of the sensors, the position Xm, Ym, Zm of target 150, which is determined in correspondence to each of the three example points in the path 310, may vary. These three calculations of position Xm, Ym, Zm are represented in the figure by 350A, 350B, 350C. As one non-limiting example, provided purely for ease of exposition, the true value Xt may be Long-1 degrees, while at 350A a value of Xm= Long-1 + delta- 1 degrees may be calculated (with an error from the true value of delta- 1 degrees). (In the presentlt disclosed subject matter, terminology such as Long-1, Lat-2, angle-3, distance-4, delta-5 etc. refers to example numeric value.) At 350B, for example, a different value of Xm= Long-1 + delta-2 degrees may be calculated (with an error from the true value of delta-2 degrees).

Attention is now drawn to Fig. 4A, schematically illustrating an example generalized view of axes, in accordance with some embodiments of the presently disclosed subject matter. View 490 shows a set 495 of coordinate axes. For convenience, roll axis R, pitch axis P, and yaw axis Y can be conventionally defined with respect to UAV 110. Roll axis R is parallel to or co-axial with a longitudinal axis 113 of UAV 110. Pitch axis P is generally in lateral and orthogonal relationship to roll axis R (i.e., parallel to the horizontal when the body is at a zero roll angle). Yaw axis Y is in orthogonal relationship to roll axis R and pitch axis P (i.e., parallel to the vertical when the body is at a zero pitch angle). Thus, the UAV 110 can in some cases have roll, pitch and/or yaw angles.

Attention is now drawn to Fig. 4B, schematically illustrating an example generalized view of fixed sensor errors, in accordance with some embodiments of the presently disclosed subject matter.

UAV 110 travels along its longitudinal axis 113. An example sensor 450 is installed in or on the UAV. For ease of exposition only, sensor 450 is shown in the figure as attached to the outside of the UAV. In some examples, sensor 450 can be an INS. In some examples, sensor 450 can be a compass. In the non-limiting example of the figure, system and mission requirements require that sensor 450 be installed in an axis 460 that is parallel to UAV's axis 113. However, in some examples it is difficult to achieve full alignment of the two axes when performing installation of sensors. Such an ability may require the use of costly tools, equipment and/or techniques, that are not always available. Therefore, in the example the installation was done such that sensor 450 is installed such that its relevant axis 465 is oriented at an error angle H with respect to the desired axis 460. In some examples, this is a source of a fixed error in the sensor, in that the angle H is not expected to change to any appreciable extent until the sensor 450 is removed by a technician, and/or until maintenance is performed on the sensor 450. This fixed error is also referred to herein as a fixed sensor inaccuracy. As one non-limiting example, for clarity of exposition, if a compass is installed delta-3 degrees off of the UAV's axis, then a compass reading of "North" can mean that the UAV itself is in fact facing delta-3 degrees from North. Since the systems of the UAV, that perform tasks related to target acquisition and locating, are in some examples unaware of this installation error, in some examples these systems do not compensate for the error when performing calculations related to locating the target 150 based on sensor measurements. Similarly, fixed inaccuracies in INS 450 will cause errors in determination of the pitch and/or roll of UAV 110, for example.

The figure shows an additional sensor, 410, 420, e.g. a target-locating sensor such as a camera and/or a range finder. In the example, it is installed below the UAV 110. In some examples, this is the sensor which has a vector 170, of the sensor's line of sight to the target 150, disclosed with reference to Fig. 1. Dashed line 410 depicts the sensor's installed state, when it has a zero (0) depression angle with reference to UAV 110. Again, in the non-limiting example of the figure, system and mission requirements may indicate that sensor 410 should be installed in an axis 413 that is parallel to UAV's axis 113. However, in some examples it is difficult to achieve full alignment of the two axes when performing installation of sensors. Therefore, in the example, the installation was done such that sensor 410 is installed such that its relevant axis 417 is at an error angle F with respect to the desired axis 413. In some examples, this too is a source of a fixed error in the sensor 410. Certain sensors, e.g. camera 410, are configured for rotation in one or more axes of the UAV, e.g. to be able to record images in various directions. Thus, sensor 410 can be, in parts of the target-locating mission, oriented to an axis 423, that is different from the installation axis 417. This situation is shown in the solid-line representation 420 of this sensor. In the example of the figure, the camera or sensor 420 is oriented downward, e.g. to capture images of a ground target from the air. The mechanical vector of sensor 420 is along axis 423, referred to herein also as mechanical axis 423. Vector 423 is at varying depression angle D with respect to the horizontal axes 113, 413

However, in some examples the optical vector 426 of sensor 420, that is the vector of the axis associated with the view of the sensor and of image capture, can be not in alignment with the mechanical vector 423. In some examples, optical line of sight vector 426 is referred to herein also as optical axis 426. This possible misalignment between the mechanical vector 423 and optical vector 426 is denoted by angle G. Thus, the optical vector 426 is at an angle K relative to the horizontal axis 413. The misalignment represented by angles H and F are examples of sensor inaccuracies associated with installation of sensors 450, 410 in the UAV 110. The misalignment represented by angle G is an example of sensor inaccuracies associated with boresight error.

In some examples, this misalignment angle G is a function of the depression angle D. As one non-limiting example, presented only for clarity of exposition, it may be, for certain sensors, that if depression angle D is angle-1 degrees, the misalignment angle G is delta-4 degrees, while for depression angle D of a value of angle-2degrees, the angle G is equal to delta-5 degrees.

Angle A of vector 170 in Fig. l is a function at least of the attitude or orientation of UAV 110 with respect to the coordinate axes of the Earth, as well as of the angles of the imaging or locating sensor 170 with respect to UAV 110. It is thus clear that the various example misalignments and angular errors disclosed with reference to this figure impact the accuracy of the determination of the angle A of vector 170. Note also that only two sensors are shown in the figure, for ease of exposition of the subject matter. In some examples, fewer or more sensors are utilized for the mission, e.g. as disclosed further herein with reference to Fig. 7.

Note that the figure discloses only axes, angles and misalignments relevant to the side view presented. It will be readily apparent to the skilled person that the same principles disclosed herein are relevant, mutatis mutandis , also to axes, angles and misalignments relevant to an aerial view (such as disclosed with reference to Fig. 2) and to other views. For example, while camera 420 depression angle D is shown, in some examples the camera 420 has an azimuth angle as well, not shown.

Note also that, for purposes of ease of exposition, the presently disclosed subject matter is presented with reference to the non-limiting example of an Unmanned Aerial Vehicle. It is readily apparent that the subject matter disclosed herein applies as well to other aerial vehicles and aircraft, e.g. an airplane, a helicopter, a balloon or a multirotor. Similarly, the presently disclosed subject matter is relevant also for water-craft such as boats and ships and the like, as well as for ground vehicles. Note that in the case of water craft and ground vehicles, the paths of travel disclosed herein are not flight paths. Note also that in some non-limiting examples, the target-locating mission determines location, e.g. coordinates, in only certain coordinate axes of the Earth, e.g. Long-Lat but not altitude etc.

All of the angles, distances, vectors, calculations, sensors and techniques described herein for determining target 150 location, with reference to Figs. 1 to 4B, are presented as non-limiting examples, for ease of exposition only. Other angles, distances, vectors, calculations, sensors and techniques, for example those known per se, can be utilized in some examples, mutatis mutandis.

Attention is now drawn to Fig. 5A, schematically illustrating an example generalized view of a calibration mission, in accordance with some embodiments of the presently disclosed subject matter. In some examples, a calibration mission 505, e.g. a calibration flight mission 505, may be used to enable correction errors in determination of the location of target 150 in a situation of fixed sensor inaccuracies, for example using a process such as disclosed further herein with reference to Figs. 9A and 9B. Example calibration mission 505 involves flight along a path of travel 578, which in the example is a flight path in the area of one or more known-location targets 550. In some examples, this path 578 is referred to herein also as a first path of travel, a first path of motion, or a first flight path. Note that the sensors associated with the UAV record measurements at a plurality of the second points along path 578. In the example of the figure, three typical points P, R, S of this plurality are shown. In some examples, these recorded measurements are referred to herein also as first measurements, and these plurality of points are referred to as a first plurality of points. Note that the corresponding first measurements recorded at each such point along the path are not necessarily the same, and that they may be a function of the position and attitude of the UAV and of the sensors at each point.

In some examples, such a mission can provide measurement data, referred to herein also as first measurement data, which is indicative of the first recorded measurements. In some examples, the first measurement data is referred to herein also as calibration data. In some examples, the first measurement data is indicative of coordinates of the known-location target(s) 550. In some examples, these coordinates are referred to herein also as first measured position information.

As disclosed further herein, the calibration data can enable the deriving of corrected second measurement data based on the second measurement data associated with target-locating mission 100. This in some examples can enable a determination of the location information of the other target(s) 150 with increased accuracy, as compared to a determination of the location information utilizing uncorrected second measurement data. This determination of the location information with increased accuracy is referred to herein also as a first determination, while the determination of the location information utilizing uncorrected second measurement data is referred to herein also as a second determination.

Known-location target 550 is a target whose coordinates are known to a defined accuracy. This defined accuracy is in some examples dependent on the needs and requirements of the particular positioning/locating application or service, in that a higher accuracy in the known position of 550 can provide more accurate correction data to be used in target-locating mission 100, 200, 300. For ease of exposition, the known coordinates of a known-location target 550, in a defined set of axes, are denoted herein as Xk, Yk, and/or Zk. The known coordinates are referred to herein also as known position information. In some examples, it is preferable that the known-location target is a fixed-location target. In some examples, known locations are based e.g. on maps. In some examples, known locations are based e.g. on surveyor surveys, which in some cases gives higher accuracy than do maps. In some examples, known-location target 550 functions as a calibration standard for the system comprising the UAV 110, its sensors 420, 450, and the target-positioning system (disclosed further herein) which utilizes these sensors.

At points P, R, S in the calibration flight path the first measurement data enables determination of first measured position information associated with each such point. For example, the measurements recorded at point P yield first measured position information of Xmkp=Long-2 + delta-6 degrees West, Ymkp= Lat-2 + delta-7 degrees North (where "mkp" denotes "a known-location target measured at point P"). Similarly, the measurements recorded at point R yield first measured position information of e.g. Xmkr= Long-2 + delta-8degrees West, Ymkr= Lat-2 + delta-9 degrees North (where mkr denotes "a known-location target measured at point R"). If the coordinates of target 550 are known to be e.g. Xk= Long-2 degrees, Yk= Lat-2 degrees, within a defined accuracy, it can be determined that at point P the determination of the location of 550 is inaccurate by delta-6 degrees Long (referred to herein also as correction X-delta) and delta-7 degrees Lat (referred to herein also as correction Y-delta), and that at point R the determination of the location of 550 is inaccurate by delta-8 degrees Long and delta-9 degrees Lat. Thus, for each such point P, R, S on the path of travel 578, the positioning error associated with the combination of the sensors of UAV 110 can be known. In this way, correction data associated with each point of the first plurality of points can be derived, by comparing the first measured position information to the known position information. This positioning error is one non-limiting example of correction data. Note that in some examples the accuracy of the correction data is dependent on the defined accuracy of knowledge of the location of known-location target 550.

In some examples, the correction data correspond to one or more coordinate axes of the known-location target(s) 550. For example, the correction data may be associated with longitude, latitude and/or altitude. In some cases, each correction datum of the correction data corresponds to one coordinate axis of one or more coordinate axes of the known-location target(s) 550 - e.g. a correction datum for the X axis, and/or one for the Y axis etc.

In some examples, the correction data can be applied to second measurement data recorded at various points along the path of location mission 100, to account for the fixed sensor accuracies as disclosed for example with reference to Fig. 4B. As indicated above, this can in some examples enable correction of the second measurement data, in a situation of fixed sensor inaccuracies. This in turn can, in some examples, enable a determination of the location information of the other target(s) 150 with an increased accuracy, as compared to a determination of the location information utilizing the uncorrected second measurement data. Recall that in some cases, such as e.g. a target area in a desert or other featureless terrain, other ways of determining with accuracy the position or other location information of target(s) 150, ways that are not compromised by the fixes sensor inaccuracies, may not be available. Details on obtaining and utilizing correction data based on calibration missions are exemplified further herein with reference to Figs. 9A and 9B.

In some cases, the one or more calibrations missions 505 precede the target- location mission(s) 100. In some such examples, as will be disclosed further herein, the correction data can be, for example, stored, and later utilized in real-time or near-real time to correct second measurement data. In other cases, the calibration mission(s) 505 follows the target-location mission(s) 100. In some such examples, the correction data can be used to correct second measurement data which was acquired at an earlier point in time.

As disclosed earlier, in some examples it is preferable that the known-location target is a fixed-location target 550. Non-limiting examples of a fixed-location target include a ground structure, a tree, a road junction (e.g. "the junction of Route 43 and Highway 8"), and a street junction (e.g. "the junction of Main Street and Broadway" or "Union Square"). Non-limiting examples of a ground structure are a building and a tower. In some such cases, the first measured position information is associated with a particular location within the ground structure.

As will be disclosed with reference to Fig. 6, in some examples it is desirable to perform the calibration mission(s) such that a variety of measurements are gathered, representing for example a variety of orientations of the sensors and/or of the UAV 110, with respect to one or more coordinate axes of the Earth, and a variety of orientations of the sensors with respect to one or more coordinate axes of the UAV. In some examples, it is desirable that the path(s) of travel include a variety of positions (e.g. Long, Lat and/or Altitude) of the sensors, and/or of the UAV, with respect to the known-location object(s) 550, and/or a variety of distances between the sensors, and/or the UAV, and the known-location object(s) 550. For example, in some cases the first path of travel includes flight at a plurality of altitudes. In some examples, the calibration process comprises performance of multiple calibration missions. Such a variety can in some cases provide more robust calibration data.

For example, in some cases the first path of flight comprises movement at a plurality of distances from the known-location target(s) 550. In the particular example of Fig. 5A, the path of flight includes flight over the known-location target(s). Fig. 6 further herein discloses another example, that of a straight path of travel that is located to one side of a target. Other flight patterns are possible.

Attention is now drawn to Fig. 5B, schematically illustrating an example generalized view of a calibration mission, in accordance with some embodiments of the presently disclosed subject matter. In this side view 580, there is shown an example of a path of travel that includes points at a plurality of altitudes. The UAV is flying at a diagonal with respect to the horizon. At a first point 584 of the mission flight path 578, the UAV 110 is at a first altitude 590 with respect to sea level 140. At another, second, point 586 of the flight path 578, the UAV is at a second altitude 595 with respect to sea level 140. The sensors can record measurements at various points, at various altitudes, along path 578.

Attention is now drawn to Fig. 6, schematically illustrating an example generalized view of a target-location mission, in accordance with some embodiments of the presently disclosed subject matter. In the example of target-location mission 680, the UAV 110 travels in the target area in a straight line second path of travel 688. The UAV 110 is recording, with its associated sensors, measurements so as to determine the location of target 150, whose location is not a priori known. In the particular non limiting example of the figure, the target 150 is always to the left of the UAV as the UAV passes it. Mission 680 is an example of missions 100, 200 and 300.

The figure shows five examples points Q', R', R', T', S' along the target-location mission second path of travel 688. These points are examples of point in the second plurality of points that correspond to points Q, P, R, S in the first plurality of points, associated with calibration mission(s). These corresponding points meet one or more similarity criteria. For example, in the example there is correspondence between points P and P', between R and R' and between S and S', as will be shown.

In some examples, the similarity criteria relate to orientations of one or more sensors. Such criteria are referred to herein also as first similarity criteria. In some examples, the correspondence is that, for corresponding points in the first plurality P, Q of points and second plurality P', Q' of points, orientations of one or more of the sensors 420, 450 meet a first similarity criterion. In some examples, first orientations of the sensor(s), associated with the first plurality of points, correspond to second orientations of the sensor(s), associated with the second plurality of points.

One example of such a first similarity criterion is that in the corresponding points, there is a correspondence of the orientations of the relevant sensors relative to at least one coordinate axis of the Earth. In one non-limiting example of this, the first similarity criterion is that these orientations are the same. As one example, at both point P of the calibration mission, and point P' of the target-location mission, the compass shows angle-3 degrees East of North, and the INS shows a roll angle of angle-4 degrees relative to the Earth, e.g. to within a defined tolerance.

Another example of a first similarity criterion is that in the corresponding points, there is a correspondence of the orientations of the relevant sensors relative to at least one coordinate axis of the UAV 110. In one non-limiting example of this, the first similarity criterion is that these orientations are the same. A non-limiting examples is that at both point R of the calibration mission, and at point R of the target-location mission, the camera 420 is at a depression angle of angle- 1 degrees relative to the UAV, e.g. to within a defined tolerance.

Note that in some examples correspondence of the orientations of the relevant sensors relative to at least one coordinate axis of the UAV 110, and correspondence of the orientations of the relevant sensors relative to at least one coordinate axis of the Earth, are not the same. For example, it may be that in point R the UAV is flying at a zero (0) degree elevation angle E from the horizon 117, and imaging sensor 420 is pointing straight ahead of the UAV, i.e. the depression angle D is 0. At point R', the UAV is flying at a minus-angle- 1 degree elevation angle E from the horizon 117, and imaging sensor 420 is pointing straight ahead of the UAV, i.e. the depression angle D is 0. In such a case, the orientation of sensor 420 is a minus-angle- 1 degree angle from the horizon 117, and there is thus no correspondence at points R and R of the orientations of the sensor 420 relative to at least one coordinate axis of the Earth. However, since at both points angle D is 0, there is correspondence at points R and R of the orientations of the sensor 420 relative to at least one coordinate axis of the UAV 110. Similarly, at another point U (not shown) of first path 578, the UAV is flying at a zero (0) degree elevation angle E from the horizon 117, and imaging sensor 420 is pointing at a depression angle D of minus-angle- 1 from the UAV. In such a case, there is a correspondence at points U and R' of the orientations of the sensor 420 relative to at least one coordinate axis of the Earth. However, there is no correspondence at points U and R of the orientations of the sensor 420 relative to at least one coordinate axis of the UAV 110. Therefore the misalignment G between the optical vector 426 and the mechanical vector 423 can be different, since in some examples, this misalignment is a function of the depression angle D of the sensor 420 with respect to axis 113 of UAV 110. Thus this particular aspect of the sensor error may not correspond at points U and

R'.

As still another example of a first similarity criterion, at both point S of the calibration mission, and point S' of the target-location mission, the range finder 420 is at a depression angle of angle- 1 degrees relative to the UAV, and also the compass shows angle-3. Note that all values disclosed herein are presented for purposes of exposition only.

In some examples, a sensor error(s), associated with sensor(s) and with one or more points of the second plurality of points P', Q' R etc., is determined, based at least on the correction data. As one example, the correction data may indicate that at point P of calibration mission 505 the compass has a sensor error of delta-3 degrees. It can be determined, based on this correction data, that also at point P' of locating mission 680 the compass has a sensor error of delta-3 degrees. Thus, the second measurement data is adjusted, utilizing the sensor error(s), thereby deriving corrected second measurement data. Similar corrections can be performed for other points on Q', R, S', T' on the second path. Note that determined sensor errors that are angular errors can be with respect to coordinate axes of the UAV, and/or with respect to coordinate axes of the Earth.

In some examples, based at least on the corrected second measurement data and on the second measured position information, e.g. Xm, Ym, Tm, obtained at each such point of travel on the second path, the location information of the target(s) 150 can be determined, in some cases yielding a location of the target 150 that is closer to Xt, Yt, Zt, and is thus more accurate, than can be derived from the uncorrected second measurement data. This location of the target can, in some examples, be output to external systems.

In some examples, the corrected second measurement data is used directly, to derive corrected second measured position information, using techniques such as those techniques, e.g. those known per se, that are used to derive second measured position information from second measurement data. In some other examples, second measured position information, e.g. Xm, Ym, Tm, associated with one or more points of the second plurality of points P', Q' R' etc., can be adjusted, utilizing the correction data, thereby deriving corrected second measured position information associated with those points. As one example, at point P' of locating mission 680 the second measured position information, e.g. the location of target 150, is measured as Xm= Long-3 + delta- 1 degrees, Ym= Lat-3 + delta- lOdegrees. In this example, the true value of the target location is Xt= Long-3 degrees, Yt= Lat-3 degrees. The correction data may indicate that at point P of calibration mission 505 the determination of the location of 550 is inaccurate by delta-6 degrees Long and delta-7 degrees Lat. This correction data, referred to herein also as correction-X-delta, correction-Y-delta, can be utilized to adjust the second measured position, thereby deriving corrected second measured position information, associated with point P', of Xm-corrected= Long-3 + delta- 1 - delta- 6degrees, Ym-corrected= Lat-3 + delta-10 - detla-7degrees. Note that the corrected second measured position information Xm-corrected, Ym-corrected is more accurate, i.e. is closer to the true Xt, Yt, than is the uncorrected second measured position information Xm, Ym. Similar corrections can be performed for other points Q', R', S', T'. In some examples, the corrected second measured position information of the various second points can be analyzed to derive a location of the target 150, and this can be output to external systems.

Note that in some examples the points that correspond on the two paths are not necessarily in the same order - some or all of them may be in a different order. For example, in path 578 the order of the points is P, R and S, while in the path 688 the order of the corresponding points is R', P', S'. However, since points were found in the calibration missions that meet similarity criteria with respect to corresponding points in the target-location mission 680, the relevant correction data derived in calibration mission 505 can be utilized to correct second measurement data associated with target- acquisition mission 680.

In other non-limiting examples, there is no direct correspondence between individual points, such as that disclosed in the example of points P and P'. As one example of this, point T has no single point on the calibration missions' paths with direct correspondence. However, by interpolating between orientation data (for examples) associated with points P and S, a correspondence is found for point T'. In some such examples, the correction of the second measurement data utilizes interpolation of the correction data. In some other examples, correction of the second measurement data utilizes extrapolation of the correction data. In at least this sense, there is a correspondence between first points P, S and second point T', and the these corresponding points meet one or more similarity criteria.

Similarly, correspondence need not be only between points in individual target- location missions and calibration missions. For example, point Q' on second path 688 does not correspond to any point on path 578 associated with calibration mission 505, but it does have a correspondence with a point Q on the path of another calibration mission of the same UAV 110, a mission which is not depicted in Fig. 4B. Here, too, there is correspondence between points Q of the first plurality of points and points Q' of the second plurality of points.

Similarly, in some examples the speed of the UAV in the calibration mission 505, and in the target-location mission 680, are the same, while in other examples the speeds in the two missions are not the same.

The example of Figs. 5B and 6 is of first 578 and second 688 paths of travel that are different, but where there is a correspondence of points. In some other examples, the first path of travel corresponds to the second path of travel. For example, in an example not depicted in Fig. 6, the second path of travel is over the target 150, and thus has additional similarities to the relevant calibration first path 678. The first path and second paths in some examples are at the same or different altitudes. The first path and second paths in some examples are at the same or different distances from target 150. The first paths and second paths in some examples are in the same or different directions. As a non-limiting example, in some examples a calibration mission 505 flown North to South can be used to derive correction data that can enable correction of data associated with a target-location mission 680 that is flown South to North. In some non-limiting examples, the first and second paths match.

In some non-limiting examples, the calibration mission 505 first path 578 is such that the known-location target 550 is to the right of UAV 110, while the operational mission 680 second path 688 is such that the other target 150 is to the left of UAV 110. One example case where such different paths have corresponding points is where the sensor of interest is imaging sensor 420, and the similarity criterion of interest is that the depression angle D is equal to angle- 1 degrees. Since in both missions the similarity criterion is met, the fact that in each mission 505, 680 the UAV 110 passes on a different side of its respective target 550, 150 does not negate the correspondence of the first P, R and second R', T' plurality of points that meet the similarity criterion.

Note also, that in some examples, the standard second path(s) 688 of flight 688 of UAV 110, utilized in target-location mission(s) 680, is determined based on manufacture recommendations for one or more of the relevant sensors 450, 410. Such recommendations may in some cases be based on utilizing the optimum performance of the sensor(s). In some examples, these recommendations are also considered when choosing the first path(s) 578 of flight used in the calibration mission(s) 505. In some examples, the expected flight patterns 688 of the operational target-location mission(s) 680 are considered when choosing the first path(s) of flight 578 used in the calibration mission(s) 505. In some examples, a close matching of calibration and operational flight patterns provides correction data that can provide comparatively more accurate locating results in the operational target-location mission(s) 680.

Note also, that in some examples, the greater the correspondence between points of the first and second pluralities of points, for example between the first 578 and second 680 flight paths, the higher the accuracy of positioning of operational target 150 that can be obtained by utilizing correction data for points P, Q, S of calibration mission 505. As a first non-limiting example, consider a case where calibration mission 505 was performed at distances between distance- 1 and distance-2 km from target 550. The resulting correction data can in some cases provide a higher-accuracy correction of second measurement data for an operational target-locating mission 680 performed at a distance of distance-2 * 1.2km from target 150. On the other hand, in some cases it can provide a relatively lower-accuracy correction of second measurement data for a different operational target-locating mission 680 performed at a distance of distance-2 * 6km from target 150.

As a second non-limiting example, consider a case in which calibration missions 505 are performed with depression angle D in the ranges of angle- 1 to angle-2 degrees. This mission may in some cases provide correction data that enable comparatively lower accuracy in positioning for a target-locating mission 680 in which the depression angle is in the range of angle- 1 * 5 to angle-2 * 5degrees, as compared to the positioning accuracy for a mission 680 in which this angle is in the range of angle-1 * 1.2 to angle-2 * 1.2 degrees.

In some examples, the similarity criteria relate to relative positions, of one or more sensors 420, 450 and of a corresponding target 150, 550, and/or relative positions of the UAV 110 and of a corresponding target. They are referred to herein also as second similarity criteria. In some examples, at corresponding points in the first plurality of points and second plurality of points, relative positions, of the sensor(s) and of a corresponding target, meet the one or more second similarity criteria. In some examples, at corresponding points in the first plurality of points and second plurality of points, relative positions, of the UAV and of a corresponding target, meet the second similarity criteria. In some examples, first relative positions of the sensor(s) and of known-location target 550, associated with the first plurality of points, correspond to second relative positions of the sensor(s) and of other target 150, associated with the second plurality of points. In some examples, first relative positions of the UAV 110 and of known-location target 550, associated with the first plurality of points, correspond to second relative positions of the sensor(s) and of other target 150, associated with the second plurality of points

To illustrate this, sensor 420 may be for example a camera, and attached to the camera is a range finder (not shown), installed to point along the same axis as the optical axis as the camera. Both thus rotate together relative to UAV 110. The range finder fixed error in some examples is a function of distance from the target. For example, at a range of distance-1 kilometers (km) the range finder has an error of delta- 11 meters (m), while at a range of distance-2kilometers it has an error of delta- 12 m. Note also that in this example there may additionally be fixed errors of the sensor associated with orientation. Since in some examples the two sensors are not installed perfectly parallel to each other, there is a misalignment between their lines of sight. In some examples this misalignment may change as sensor 420 rotates, since the misalignment G between the optical vector 426 and the mechanical vector 423 of the camera are in some cases a function of angle D. Thus, in some examples there is a correspondence between first line-of-sight vectors (not shown) from the sensor(s) 420 to the known-location target(s) 550, at points P, R in the first plurality of points, and second line-of-sight vectors 170 from the sensor(s) 420 to the other target(s) 150, at points P', R in the second plurality of points.

In some examples, one or more corresponding points of the first plurality P, Q, R, S and second plurality P', Q', R, S', T' of points meet both first and second similarity criteria.

In general, the calibration mission(s) 505 in some examples includes measurements recorded at points with a sufficiently rich set of orientations of the various sensors (e.g. orientations with respect to one or more coordinate axes of the Earthand/or of the UAV 110), and in some cases with a sufficiently rich set of positions and/or distances of the various sensors, relative to the known-location target 550, such that a system, disclosed e.g. with reference to Figs. 7 and 8, is capable of correcting second measurement data for all points along target-location paths 688 that include any orientation of the various sensors, and in some cases any position and/or distance of the various sensors, relative to other target 150. As a non-limiting example, calibration mission path 578 includes points at which the imaging device 420 is at depression angles of angle-6 and angle-7 degrees, while the second path 688 includes points at which the device 420 is at depression angles of angle-land angle-2degrees. Although the second path 688 includes no points with depression angles of angle-6 and angle-7 degrees, the system is able to correct the second measurement data of mission 680 using the correction data derived from calibration mission 505, for example using interpolation and/or extrapolation.

In the above non-limiting examples, the correspondence of first and second points, and the first and second similarity criteria are associated with orientations and/or range being equal to each other, for example to within a defined amount (e.g. the orientation is the same to within delta-12 degrees) - whether via a direct correspondence of individual points, or for example using interpolation and extrapolation. In the above non-limiting examples, the correspondence of first and second points is associated with orientations being equal to each other, for example to within a defined amount (e.g. the orientation is the same to within delta-12 degrees). In other non-limiting examples, the correspondence and the similarity criteria can be of a more general nature. For example, calibration mission 505 may show that for depression angles D in the range of angle-1 to angle-2 degrees, the misalignment of the optical and mechanical axes is delta-4 degrees, based on first points P, R, S with depression angles in this range. The correction data may in such a case indicate that for all points in operational mission 680 with angle D in the angle-1 to angle-2 degree range, the above error should be assumed to be delta-4 degrees. In some examples, the standard error associated with this range of angles for this sensor has thus been learned. Such an error can then be applied to a second point T in the mission 680. There thus is a correspondence of points P, R, S to point T, without the use of e.g. interpolation or extrapolation. A similar approach, exemplified above for ranges of angles, can, in some examples, be used for ranges of distances.

Note also that the calibration process in some examples provides best results, providing correction to comparatively higher accuracy, when the process and its resulting correction data is utilized for a particular vehicle 110 and its particular sensors 450, 410. The correction data derived from a calibration mission(s) 505 for UAV #1, with particular sensors INS #1 and Camera #1, which were, for example, installed with particular misalignments, may in some cases yield less accurate corrections of target location for a target-location mission(s) 680 performed by UAV #2, even one of the same model as UAV #1, which has sensors INS #2 and Camera #2 which may have been, for example, installed with different misalignments. Similarly, in some examples the correction data derived from a calibration mission(s) 505 for UAV #1 may yield less accurate corrections of target location for target-location mission(s) 680, performed by the same UAV #1, at a point in time where one or more of the INS #1 and Camera #1 have undergone, for example, maintenance, removal and re-installation, or even replacement (e.g. by INS #3). Since the relevant sensor accuracies in such cases are no longer fixed, but have changed, in some examples it may be advantageous to re-perform calibration missions 505. The decision is in some cases based on operational need.

Note that in the above discussions, the first measured position information, associated with known-location target 550, and the second measured position information, associated with the other target 150, are indicative of coordinates of the respective target with reference to coordinate axes of the Earth. In some other examples, the first measured position information and the second measured position information are indicative of one or more known orientation angles, of the known-location target(s), and of one or more orientation angles of the other target(s), in one or more orientation directions. The one or more orientation angles of the other target(s) are referred to herein also as one or more second orientation angles. As a non-limiting example of this, the first measured position information is indicative that known-location target 550 is facing Northwest, and the second measured position information is indicative that other target 150 |is facing East. In some other examples, the first measured position information and the second measured position information are indicative of both coordinates of the respective target and of one or more known orientation angles of the respective target.

Note that in some examples, calibration mission 505 is repeated a number of times, to improve the accuracy of the correction data. This may be done, for example, when high accuracy location is required in the target-locating mission 680.

Details of example systems configured for correction of the second measurement data associated with target-locating mission 680 are disclosed further herein with reference to Figs. 7 and 8. Details of example methods for correction of the second measurement data are disclosed further herein with reference to Figs. 9A and 9B.

Attention is now drawn to Fig. 7, illustrating an example generalized schematic diagram of a calibrated target-locating system 700, in accordance with some embodiments of the presently disclosed subject matter. Calibrated target-locating system 700 is also referred to herein as a calibrated target-positioning system 700.

In some examples, system 700 comprises a target-locating system 720. Target- locating system 720 is in some examples referred to herein also as a target-positioning system720. In some non-limiting examples, target-locating system 720 includes a computer. It may, by way of non-limiting example, comprise a processing circuitry (not shown). This processing circuitry may comprise a processor (not shown) and a memory (not shown). This processing circuitry may be, in non-limiting examples, general- purpose computer(s) specially configured for the desired purpose by a computer program stored in a non-transitory computer-readable storage medium. They may be configured to execute several functional modules in accordance with computer-readable instructions. In other non-limiting examples, this processing circuitry may be a computer(s) specially constructed for the desired purposes.

System 720 in some examples receives measurements recorded by various sensors, and determines the location or position of target(s) 150, 550. Non-limiting example functions of system 720 are disclosed herein with reference, for example, to Figs. 1, 2, 3, 6 and 9. In some non-limiting examples, target-locating system 720 is a known per se system. In other non-limiting examples, target-locating system 720 includes at least a portion of the calibration functionality disclosed herein, e.g. with reference to the flows of Figs.9A and 9B.

In some examples, system 700 comprises one or more sensors. In some examples, target-locating system 720 is operatively coupled to one or more of: INS 730, compass 735, altimeter 745, imaging device 750 (e.g. Electro-optical or Infra-Red, e.g. a camera), and range finder 760. In some examples, target-locating system 720 is operatively coupled to a GNSS 740, e.g. Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), or Galileo. These sensors are non-limiting examples of sensors 410, 420, 450 in Fig. 4B. Note that the presently disclosed subject matter refers to systems both with and without range finders 760.

In some examples, system 700 comprises a database or other data store 715 that contains a Digital Terrain Model (DTM) or Digital Terrain Elevation Data (DTED). In some examples, this database is operatively connected to target-locating system 720. In some examples, such a database provides system 720 altitude information associated with point(s) on the terrain 145, e.g. points of targets 150, 550.

In some examples, system 700 comprises target-locating calibration system 710. Target-locating calibration system 710 is in some example referred to herein also as a target-positioning calibration system 710. A non-limiting example structure of target- locating calibration system 710 is disclosed further herein with reference to Fig. 8. In some examples, target-locating calibration system 710 receives first measurement data that is associated with calibration missions 505, and performs functions associated with calibration of sensors 420, 450 to account for fixed-sensor inaccuracies. In some examples system 710 derives correction data. Non-limiting example functions of system 710 are disclosed herein with reference, for example, to Figs. 5, 6 and 9A and 9B.

In some examples, system 700 comprises a database or data store 718 that contains known-target 550 location information. In some examples, such a data store contains location information, for example coordinates of the Earth, associated with one or more known-location targets 550. As disclosed herein, such information is in some examples used, e.g. by target-positioning calibration system 710, to calibrate the target- locating process. Data store 718 is also referred to herein as known-target location database/data store 718.

In some examples, system 700 comprises one or more external systems. The figure discloses the example of one or more ground station(s) 780, and of one or more other external systems 790. In some examples, systems 780 and/or 790 are operatively coupled to target-location system 720. In some examples, systems 780 and/or 790 are operatively coupled to target-location calibration system 710 - in addition to or instead of the coupling to target-location system 720. In some examples, ground station 780 is the same as ground station 190 of Fig. 1. Non-limiting examples of systems 780 and 790 include:

(a) interacting with UAV 110, e.g. using radio frequency, to determine the position of the UAV; (b) receiving correction data, e.g. from system 710, for use in correcting second measurement data and/or second measured position information;

(c) receiving second measurement data, e.g. from system 720;

(d) receiving second measured position information, e.g. from system

720;

(e) receiving corrected second measured position information, e.g. from system 710 and/or from system 720;

(f) receive a derived location of the target(s) 150, e.g. from system 710 and/or from system 720.

In some non-limiting examples, systems 780 or 790 derive the location of the target(s) 150, e.g. based on the corrected second measured position information.

Attention is now drawn to Fig. 8, illustrating an example generalized schematic diagram of a target-locating calibration system 710, in accordance with some embodiments of the presently disclosed subject matter. In some examples, target- locating calibration system 710 can include a computer. It may, by way of non-limiting example, comprise processing circuitry 820. Processing circuitry 820 may comprise a processor 840 and memory 830. The processing circuitry 820 may be, in non-limiting examples, a general-purpose computer(s) specially configured for the desired purpose by a computer program stored in a non-transitory computer-readable storage medium. They may be configured to execute several functional modules in accordance with computer-readable instructions. In other non-limiting examples, processing circuitry 820 may be a computer(s) specially constructed for the desired purposes.

Processor 840 may comprise, in some examples, at least one or more functional modules. In some examples it may perform at least functions, such as those disclosed further herein with reference to Figs.9A and 9B.

In some examples, processor 840 comprises input interface module 842. In some examples, this module is configured to receive first measurement data and second measurement data from target-location system 720. In some examples, this module may be configured to receive location data associated with known-location target(s) 550 from known-target location database 718.

In some examples, processor 840 comprises correction data determination module 846. In some examples, this module is configured to compare known location information of known-location target(s) 550 to first measured position information. In some examples, the module thereby derives correction data associated with one or more points P, R of the first plurality of points of e.g. first path of travel 578.

In some examples, processor 840 comprises sensor error calculation module 844. In some examples, this module is configured to determine, based at least on the correction data (e.g. derived by module 846), sensor error(s) associated with the sensor(s) and with one or more second points P', Q' of the second plurality of points of e.g. second path of travel 680.

In some examples, processor 840 comprises second-measurement-data correction module 851. In some examples, this module is configured to adjust the second measurement data, utilizing at least the sensor error(s) (e.g. derived by module 844). In some examples the module thereby derives corrected second measurement data. In some other examples, part or all of such functionality is instead performed by a module (not shown) of the processor (not shown) of target-positioning system 720.

In some examples, processor 840 comprises target-location data correction module 853. In some examples, this module is configured to adjust, utilizing the correction data (e.g. derived by module 846), the second measured position information, e.g. measured position coordinates Xm, Ym, associated with one or more second points P', Q' of the second plurality of points. In some examples the module thereby derives corrected second measured position information associated with one or more second points P', Q' of the second plurality of points. In some other examples, part or all of such functionality is instead performed by a module (not shown) of the processor (not shown) of target-positioning system 720.

In some examples, processor 840 comprises target-location calculation module 855. In some examples, this module is configured to determine the location information (e.g. coordinates) of the other target(s) 150, based at least on the corrected second measurement data (e.g. derived by module 851). In some examples, this module is configured to determine the location information (e.g. coordinates) of the other target(s) 150, based at least on the corrected second measured position information (e.g. derived by module 853). In some other examples, part or all of such functionality is instead performed by a module (not shown) of the processor (not shown) of target-positioning system 720.

In some examples, processor 840 comprises output interface module 843. In some examples, this module is configured to send output data, for example, to one or more of target-location system 720, ground station 780 and other external systems 790. Non-limiting examples of data that in some cases is output via this module include:

(a) correction data;

(b) sensor error(s) associated with the sensor(s) and with one or more second points P', S'; (c) corrected second measurement data;

(d) corrected second measured position information;

(e) the location information (e.g. coordinates) of the other target(s) 150.

As already indicated, example functions of these modules are disclosed further herein with reference to Figs. 9A and 9B. In some examples, memory 830 of processing circuitry 820 is configured to store data associated with at least the calculation of various parameters disclosed above with reference to the modules. As another non-limiting example, memory 324 in some cases stores correction data.

In some examples, target-locating calibration system 710 comprises data storage 870. In some examples, storage 870 stores data that is relatively more persistent than the data stored in memory 830. For example, correction data can be stored, so as to be- reused in multiple target-positioning missions 680. In other examples, other divisions of data between storage 870 and memory 830 may exist. In some examples, target-locating calibration system 710 comprises input interfaces 890 and/or output interfaces 880. In some examples, 880 and 890 interface between the input interface module 842, and the output interface module 843, respectively, of processor 840, and various systems external to system 710.

Example advantages of utilizing such systems 700, 710, as disclosed with reference to Figs. 7 and 8, are disclosed further herein with reference to flow diagram

Fig. 9A and 9B.

Figs. 4B, 7 and 8 illustrate only a general schematic of the system architecture, describing, by way of non-limiting example, certain aspects of the presently disclosed subject matter in an informative manner, merely for clarity of explanation. It will be understood that that the teachings of the presently disclosed subject matter are not bound by what is described with reference to Figs. 4B, 7 and 8.

Only certain components are shown, as needed, to exemplify the presently disclosed subject matter. Other components and sub-components, not shown, may exist. Systems such as those described with respect to the non-limiting examples of Figs. 4B, 7 and 8 may be capable of performing all, some, or part of the methods disclosed herein.

Each system component and module in Figs. 4B, 7 and 8 can be made up of any combination of software, hardware and/or firmware, as relevant, executed on a suitable device or devices, which perform the functions as defined and explained herein. The hardware can be digital and/or analog. Equivalent and/or modified functionality, as described with respect to each system component and module, can be consolidated or divided in another manner. Thus, in some embodiments of the presently disclosed subject matter, the system may include fewer, more, modified and/or different components, modules and functions than those shown in Figs. 4B, 7 and 8. To provide one non-limiting example of this, in some examples the target-location data correction module 853 and target location calculation module 855 can be combined. Similarly, in some examples, there may be separate sensor error calculation modules 844 for each type of sensor (e.g. INS vs. camera). Similarly, in some examples known-target location database/data store 718 is included within data storage 870, instead of being external to system 710. One or more of these components and modules can be centralized in one location, or dispersed and distributed over more than one location, as is relevant.

Each component in Figs. 4B, 7 and 8 may represent a plurality of the particular component, possibly in a distributed architecture, which are adapted to independently and/or cooperatively operate to process various data and electrical inputs, and for enabling operations related to calibration of target-location. In some cases, multiple instances of a component may be utilized for reasons of performance, redundancy and/or availability. Similarly, in some cases, multiple instances of a component may be utilized for reasons of functionality or application. For example, different portions of the particular functionality may be placed in different instances of the component. Those skilled in the art will readily appreciate that the components of systems 710 and 720, and of data stores 670 and 718, for example, can be consolidated or divided in a manner other than that disclosed herein. In some examples, some or all of the systems, components and/or modules are located on the UAV or other vehicle 110. In some examples, some or all of the systems, components and/or modules are located in systems external to UAV 110, e.g. in a ground station 780.

Communication between the various components of the systems of Figs. 4B, 7 and 8, in cases where they are not located entirely in one location or in one physical component, can be realized by any signaling system or communication components, modules, protocols, software languages and drive signals, and can be wired and/or wireless, as appropriate. The same applies to interfaces such as 890, 880.

Attention is now drawn to Figs. 9A and 9B, illustrating one example of a generalized flow chart diagram, of a flow of a process or method 900, for calibration of a target-positioning system, in accordance with certain embodiments of the presently disclosed subject matter. This process is, in some examples, carried out by systems such as those disclosed with reference to Figs. 4B, 7 and 8.

The flow starts at 910. According to some examples, the UAV (or other vehicle) 110 performs calibration mission(s) 505, in which one or more sensors 450, 420, 730, 735, 740, 745, 750, 760 capture measurements associated with a first plurality of points P, R, S (block 910). An example mission has been disclosed herein with reference to Figs. 5A and 5B. The sensors in some examples send the recorded information to target-locating system 720. According to some examples, first measurement data is received (block 920). In some examples, this data is received from the target-positioning system 720. In some examples, this first measurement data is received by input interface module 842 of processor 840, of processing circuitry 820, of target-positioning calibration system 710, e.g. via the input interfaces 890. In some examples, the first measurement data is associated with the calibration mission(s) 505 performed by the UAV 110 in block 910, and the first measurement data is indicative of measurements recorded by the sensors, at a first plurality of points, in block 910. The first measurement data is in some examples indicative of coordinates of the known-location target(s) 550. These coordinates are also referred to herein as first measured position information.

According to some examples, known coordinates of the known-location target(s) 150, are received (block 925). In some example these coordinates are referred to herein also as known position information. In some examples, this data is received from the known-target location information data store 718. In some examples, this first measurement data is received by input interface module 842 of processor 840 of target positioning calibration system 710, e.g. via the input interfaces 890.

According to some examples, the first measured position information to the known position information are compared (block 930). In some examples, this comparison is performed by correction data determination module 842 of processor 840 of target-positioning calibration system 710.

According to some examples, correction data associated with each point of the first plurality of points P,R, S, Q are derived (block 935). This derivation can be a result of the comparison of block 930. In some examples, this block is performed by correction data determination module 842 of processor 840 of target-positioning calibration system 710.

Two example types of correction data are disclosed, as follows:

In some first cases of this example method, the correction data that is derived in block 935 comprise sensor error(s) associated with each sensor, and with one or more points P,R in the first plurality of points P, R, S, e.g. associated with calibration first path of travel 578. For example, the correction data determination module 842 can analyze the difference between the measured location coordinates of target 550 at point P, and the known-location coordinates - which was calculated in block 930. The module 842 can then determine, e.g. using known per se techniques, that an error of delta-3, in compass 735, could explain this error between the coordinates. Or the module 842 can determine, e.g. using known per se techniques, that a pitch error of delta-14 degrees in the INS 730, and an error of delta-5 degrees in optical axis 426 of imaging device 750, when the device 750 was at depression angle of angle- 1 degrees at point P, can explain the error between the coordinates. In some examples, position errors for several flight points P, R, S are analyzed, and it is determined that a pitch error of delta-15 degrees in the INS 730 can explain them all. Such correction data is used in block 968 further herein by e.g. sensor error calculation module 844.

In some second cases of this example method, the correction data that is derived in block 935 comprises corrected measured position information, associated with each sensor, and with one or more points P, R in the first plurality of points P, R, S, e.g. associated with calibration first path of travel 578. In some examples, this corrected measured position information comprises corrections in coordinates of the known- location target 550. In some examples, this corrected measured position information is referred to herein also as first corrected measured position information. For example, as disclosed with reference to Fig. 5A, the measurements recorded at point P yield first measured position information of Xmkp= Long-2 + delta-6 degrees West, Ymkp= Lat-2 + delta-7 degrees North (where "mkp" denotes "a known-location target measured at point P"). If the coordinates of target 550 are known to be e.g. Xk= Long-2 degrees, Yk= Lat-2 degrees, within a defined accuracy, it can be determined, e.g. by the correction data determination module 842, that at point P the determination of the location of 550 is inaccurate by correction X-delta= delta-6 degrees Long and correction Y-delta= delta-7degrees Lat. This determined inaccuracy of first measured position information, of delta-6 and delta-7 degrees, associated with one or more first points P of the first plurality of points P, S, R, is a non-limiting example of first corrected measured position information. Such correction data is used in block 980 further herein, in some examples, by e.g. target-location data correction module 853.

According to some examples, the correction data are stored (block 940). In some examples, this block is performed by correction data determination module 842 of the processor. For example, this data can be stored to storage 870. In some examples, this stored set of data can be used to correct location determinations performed in operational target-locating mission(s) 680. According to some examples, the same UAV (or other vehicle) 110 performs one or more target-locating missions 680, in which the same one or more sensors 450, 420, 730, 735, 740, 745, 750, 760 capture measurements associated with a second plurality of points P', Q', R', T, S' (block 950). An example mission 680has been disclosed herein with reference to Fig. 6. The sensors in some examples send the recorded information to target-locating system 720.

According to some examples, second measurement data is received (block 960). In some examples, this data is received from the target-positioning system 720. In some examples, this second measurement data is received by input interface module 842 of processor 840 of target-positioning calibration system 710, e.g. via the input interfaces 890. In some examples, the second measurement data is associated with the target- locating missions(s) 680 performed by the UAV 110 in block 950, and the second measurement data is indicative of measurements recorded by the sensors, at a second plurality of points, in block 950. The second measurement data is, in some examples indicative of coordinates of the other target(s) 950. These coordinates are also referred to herein as second measured position information.

After block 960, in some examples there are at least two methods to utilize the correction data to improve the accuracy of the location of target(s) 150. Depending on system configuration, the process may utilize one or both methods. In some examples, different methods are used for different points in the second plurality of points P', R' etc. This disclosure will consider each method in turn.

Considering the first method, according to some examples, one or more sensor errors, associated with the sensor(s) 450, 420, and with one or more second points P', R of the second plurality of points P', R, S', Q', are determined (block 968). In some examples, this determination is based at least on the correction data, derived in block 935. In some examples, this is performed by sensor error calculation module 844 of processor 840. Non-limiting examples of this calculation are disclosed herein with reference to Fig. 6. As one example, the module 844 determines that for corresponding points in the first plurality of points, e.g. P, S, and in the second plurality of points T', orientations of the sensor(s) meet a first similarity criterion. For example, the module determines that orientations, relative to one or more coordinate axes of the UAV and/or of the Earth, at both point P of the calibration mission 505 and point P' of the target- location mission 680, orientations of the sensor(s) are the same within a defined amount. The module determines that therefore at point T', the compass 735 has a sensor error of delta-3 degrees.

As another example, the module 844 determines that for corresponding points in the first plurality of points, e.g. P, S, and in the second plurality of points T', relative positions, of the UAV 110 and of a corresponding target 550, 150, meet a second similarity criterion. For example, first relative positions of the UAV 110 and of the known-location target 550, associated with the first plurality of points P, S, correspond to second relative positions of the UAV and of the other target 150, associated with the second plurality of points T'. In such a case, the module 844 determines, in a non limiting example, that for the range of distances from the target 550, of distance- 1 km to distance-2km, represented by points P and S, the range finder 760 has an error of delta- 11 m. The module determines that therefore at point T', located at a distance of distance- 3km from target 150 (which is more than distance- 1 and less than distance-2), the range finder 760 can be assumed to also have an error of delta- 11 meters.

In some examples, for points in the second plurality of points, the system now knows the extent to which each sensor's measurements have errors, and can use this information in the next block.

According to some examples, the second measurement data is adjusted, thereby deriving corrected second measurement data (block 970). In some examples, this determination utilizes the sensor error(s), determined in block 968. In some examples, this is performed by second-measurement-data correction module 851 of processor 840 of target-positioning calibration system 710. As an example, a compass reading of angle-3 degrees at point P, is adjusted by delta-3 degrees to be a reading of angle-3 - delta-3 degrees, based on the sensor error correction data for compass 735 which is associated with corresponding point P. This adjustment of the compass reading for point P is one non-limiting example of adjusting second measurement data. In some examples these adjustments enable a more accurate re-calculation of the second measured position information associated with a particular point P.

According to some examples, the location information of the other target(s) 150 is determined (block 973). In some examples, this determination is based at least on the corrected second measurement data (derived in block 970). In some examples this is based also at least on the second measured position information, e.g. Xm, Ym, Zm. In some examples, this is performed by target-location calculation module 855 of processor 840.

In some other examples, the corrected second measurement data is used directly, to derive corrected second measured position information, using techniques such as the techniques, e.g. those known per se, that are used to derive second measured position information from second measurement data. Based on the derived corrected second measured position information, the location information of the other target(s) 150 is determined.

According to some examples, the location information of the other target(s) 150 is output (block 975). In some examples, the output is to external systems such as 780, 790. In some examples, this is performed by output interface module 843 of processor 840, of processing circuitry 820, of target-positioning calibration system 710, e.g. via the output interfaces 880. In some examples, the location information of the other target(s) 150 is output together with an image of the target(s) 150.

Considering next the second method, according to some examples, in response to performance of block 960, flow continues to Fig. 9B (see reference "A"). The second measured position information is adjusted (block 980). In some examples, this adjustment utilizes the correction data, derived in block 935. In some examples, this adjustment is performed by target-location data correction module 853 of processor 840.

As one example, the correction data is first corrected measured position information, which indicates that at point P the determination of the location of 550 is inaccurate by delta-6 degrees Long and delta-7 degrees Lat. In some cases, the module 853 determines that sensor orientations, relative to one or more coordinate axes of the UAV and/or of the Earth, both at point P of the calibration mission 505 and at point P' of the target-location mission 680, meet a similarity criterion. The module determines that therefore also at point P', the determination of the location of 550 is inaccurate by delta-6 degrees Longitude and delta-7 degrees Latitude.

According to some examples, corrected second measured position information, associated with one or more second points P', Q' T' of the second plurality of points, are derived (block 983). In some examples, this adjustment is performed by target-location data correction module 853 of processor 840. Continuing the previous example, the second measured position information associated with P' is corrected, e.g. from Xm= Long-1 + delta- 16 degrees, Ym= Lat-1 + delta- 17 degrees, using the correction data of " delta-6 degrees Long and delta-7 degrees Lat" . The derived corrected second measured position information associated with P' is thus Xm-corrected= Long-1 + delta-16 - delta-6 degrees , Ym-corrected= Lat-1 + delta-17 - delta-7 degrees.

According to some examples, corrected second measured position information, e.g. derived in block 983, is output (block 985). In some examples, this output is to external systems, e.g. 780, 790. In some examples, this is performed by output interface module 843 of processor 840, of processing circuitry 820, of target-positioning calibration system 710, e.g. via the output interfaces 880. In some examples, the external systems use the received corrected second measured position information to determine location information, e.g. coordinates, of the other target(s) 150.

According to some examples, location information, e.g. coordinates, of the other target(s) 150, is determined (block 987). In some examples, this determination is based on the corrected second measured position information e.g. as derived in block 983. In some examples, this determination is performed by target-location calculation module 855of processor 840.

According to some examples, the flow then proceeds to block 975 of Fig. 9B, as shown by reference "B".

In some examples, one or more of the blocks 960, 968, 970, 975, 980, 983, 985, 987 are performed in real time, or in near-real time. In some examples, these blocks are performed utilizing the stored correction data stored in block 940. For example, the UAV 110 can receive the correction data, and at each point P', R' etc. of the second plurality of points the UAV can determine sensor errors, adjust the second measurement data, and determine the location information of the target. This is exemplified in the figure by arrow 977, which after block 973 loops back to block 950, where at the next point S' in the second path (for example) the measurements are recorded, and second measurement data is generated.

In some other examples, the second measurement data is saved and/or transferred to other systems from target-locating system 720, and at a later time it is processed and analyzed — not in real time. In still other examples, the second measurement data is saved, and the calibration mission 505 is performed after the operational mission 680. In such a case, at least the steps 968, 970, 975, 980, 983, 985, 987 are performed at a time after the mission 680, and not in real time during the mission 680.

The example flow above discloses modules of target-positioning calibration system 710 performing all of the blocks960, 968, 970, 975, 980, 983, 985, 987. In other examples, the correction data derived in block 935 is sent to target-positioning system 720, and system 720 performs the blocks 960, 968, 970, 975, 980, 983, 985, 987. Similarly, in some examples system 720 stores the correction data in block 940. In some examples, system 720 can include modules and components which are the same, or similar, to those disclosed in Fig. 8 with reference to system 710. Other divisions of the functionality between systems 710 and 720 are possible, where each system performs part of the process. Similarly, in some examples blocks 960, 968, 970, 975, 980, 983, 985, 987 are performed by systems located in the UAV 110. In some other examples, one or more of these blocks are performed by systems external to the UAV or to another vehicle, e.g. in a ground station or other ground system.

In some examples, a system such as that disclosed, for example, with reference to Figs. 7 and 8, which performs calibration processes such those disclosed with reference to Figs. 9A and 9B, can have at least certain non-limiting example advantages. As disclosed above, in some examples it is difficult to achieve full alignment of axes when performing installation of sensors, so as to prevent or minimize fixed sensor inaccuracies. Such an ability may require the use of costly tools, equipment and/or techniques, that are not always available. A calibration mission 505 can in some examples compensate for these errors, and provide correction data that will allow correction of target 150 location information, at a desired accuracy, without the need for such tools, equipment and/or techniques.

In at least this sense, in some examples, known-location target 550 can function as a calibration standard for the system comprising the UAV 110, its sensors 420, 450, and the target-positioning system 720 which utilizes these sensors. This calibration standard can function as an alternative to using calibration standards for each sensor 420, 450 to calibrate each sensor (e.g. separately).

In some examples, use of a method such as that of Figs. 9A and 9B reduces costs. In addition, in some examples this enables quicker installation of sensors, which may be advantageous from an operational point of view as well as in terms of e.g. labor cost. In some examples, such a calibration mission 505 also enables calibration in e.g. field situations where such tools and equipment are in any event unavailable to maintenance personnel of UAV 110.

In addition, in some examples, the fixed sensor inaccuracies are not expected to change to any appreciable extent until the sensor(s) 420, 450 is removed or replaced by a technician, and/or until maintenance is performed on the sensor(s). Thus a calibration mission 505 is in some cases expected to provide correction data that will allow correction of target 150 location information, at a desired defined accuracy, for all UAV missions, until one of such changes in the sensor installation is effected.

In addition, in some examples the calibration mission compensates for errors in alignment of the imaging sensor's 750 mechanical and optical axes, which are dependent on the particular depression angle D.

In addition, calibration using a calibration mission 505, in some examples enables determination of target 150 location with the required accuracy, in situations where there are no other means to obtain such locating accuracy. Recall that in some cases, such a e.g. a target area in a desert, in a body of water such as an ocean, or in other featureless terrain, there may in some cases be no other features 160 in the target area (buildings etc.) which can serve as anchoring points, or as reference points, that can be used to help determine the target's location. In such cases, other ways of determining with accuracy the position or other location information of target(s) 150, ways that are not compromised by the fixed sensor inaccuracies, may not be available.

Note that the above description of process 900 is a non-limiting example only.

In some embodiments, one or more steps of the flowchart exemplified herein may be performed automatically. The flow and functions illustrated in the flowchart figures may for example be implemented in systems 710, 720 and in processing circuitry 820, and may make use of components described with regard to Figs. 1, 4B, 7 and 8. It is also noted that whilst the flowchart is described with reference to system elements that realize steps, such as for example systems 710, 720, and processing circuitry 820, this is by no means binding, and the operations can be carried out by elements other than those described herein.

It is noted that the teachings of the presently disclosed subject matter are not bound by the flowcharts illustrated in the various figures. The operations can occur out of the illustrated order. One or more stages illustrated in the figures can be executed in a different order and/or one or more groups of stages may be executed simultaneously. For example, steps 985 and 987, shown in succession, can be executed substantially concurrently, or in a different order. Similarly, some of the operations or steps can be integrated into a consolidated operation, or can be broken down into several operations, and/or other operations may be added. As a non-limiting example, in some cases blocks 930and 935 can be combined.

In embodiments of the presently disclosed subject matter, fewer, more and/or different stages than those shown in the figures can be executed. As one non-limiting example, certain implementations may not include the output block 975, the storage block 940, and/or the method of blocks 980, 983, 985, 987.

In the claims that follow, alphanumeric characters and Roman numerals, used to designate claim elements such as components and steps, are provided for convenience only, and do not imply any particular order of performing the steps.

It should be noted that the word “comprising” as used throughout the appended claims, is to be interpreted to mean “including but not limited to”.

While there has been shown and disclosed examples in accordance with the presently disclosed subject matter, it will be appreciated that many changes may be made therein without departing from the spirit of the presently disclosed subject matter.

It is to be understood that the presently disclosed subject matter is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The presently disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present presently disclosed subject matter.

It will also be understood that the system according to the presently disclosed subject matter may be, at least partly, a suitably programmed computer. Likewise, the presently disclosed subject matter contemplates a computer program product being readable by a machine or computer, for executing the method of the presently disclosed subject matter, or any part thereof. The presently disclosed subject matter further contemplates a non-transitory machine-readable or computer-readable memory tangibly embodying a program of instructions executable by the machine or computer for executing the method of the presently disclosed subject matter or any part thereof. The presently disclosed subject matter further contemplates a non-transitory computer readable storage medium having a computer readable program code embodied therein, configured to be executed so as to perform the method of the presently disclosed subject matter.

Claims

CLAIMS:

1. A method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data being indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data being indicative of coordinates of at least one known-location target, the coordinates constituting first measured position information; b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and in the second plurality of points, orientations of the at least one sensor, meet a first similarity criterion.

2. The method of claim 1, wherein the orientations of the at least one sensor comprise orientations relative to at least one coordinate axis of the earth.

3. The method of any one of claims 1 and 2, wherein the orientations of the at least one sensor comprise orientations relative to at least one coordinate axis of the UAV.

4. The method of any one of claims 1 to 3, wherein the correction of the second measurement data utilizes at least one of interpolation and extrapolation of the correction data.

5. The method of any one of claims 1 to 4, wherein the correction data correspond to coordinate axes of the at least one known-location target.

6. The method of any one of claims 1 to 5, wherein the first similarity criterion comprises first orientations of the at least one sensor, associated with the first plurality of points, corresponding to second orientations of the at least one sensor, associated with the second plurality of points.

7. The method of any one of claims 1 to 6, wherein the at least one calibration mission is associated with a first path of flight, wherein the target-location mission is associated with a second path of flight, wherein the first path of flight corresponds to the second path of flight.

8. The method of claim 7, wherein the first path of flight comprises movement at a plurality of distances from the at least one known-location target.

9. The method of any one of claims 7 to 8, wherein the first path of flight comprises movement at a plurality of distances from the at least one known- location target.

10. The method of any one of claims 7 to 9, wherein the first path of flight comprises flight over the at least one known-location target.

11. The method of any one of claims 7 to 10, wherein the first path of flight comprises flight at a plurality of altitudes.

12. The method of any one of claims 1 to 11, wherein the fixed sensor inaccuracies comprise sensor inaccuracies associated with installation of the at least one sensor in the UAV.

13. The method of any one of claims 1 to 12, wherein the fixed sensor inaccuracies comprise sensor inaccuracies associated with boresight error.

14. The method of any one of claims 1 to 13, wherein the fixed sensor inaccuracies are associated with at least one of an imaging device, a range finder, an Inertial Navigation System and a compass.

15. The method of any one of claims 1 to 14, wherein the imaging device comprising at least one of an electro-optical (EO) device and an infra-red (IR) device.

16. The method of any one of claims 1 to 15, further comprising: c) storing the correction data.

17. The method of any one of claims 1 to 16, further comprising: d) receiving, from the target-positioning system, the second measurement data, the second measurement data being indicative of coordinates of the at least one other target, the coordinates constituting second measured position information.

18. The method of claim 17, further comprising: e) determining, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and f) adjusting the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

19. The method of the previous claim, further comprising: g) determining, based at least on the corrected second measurement data, the location information of the at least one other target.

20. The method of the previous claim, wherein the determination of the location information of the at least one other target is based at least on the second measured position information.

21. The method of any one of claims 18 to 20, wherein at least one of the steps (e), (f) and (g) is performed in real time, utilizing stored correction data.

22. The method of any one of claims 18 to 21, wherein at least one of the steps (e), (f) and (g) is performed in the UAV.

23. The method of any one of claims 18 to 22, wherein at least one of the steps (e), (f) and (g) is performed by a ground system.

24. The method of any one of claims 19 to 20, further comprising: h) outputting the location information of the at least one other target to at least one external system.

25. The method of the previous claim, wherein the location information of the at least one other target is output together with an image of the target.

26. The method of any one of claims 1 to 25, wherein for corresponding points in the first plurality of points and second plurality of points, relative positions, of the UAV and of a corresponding target, meet a second similarity criterion.

27. The method of the previous claim, wherein the second similarity criterion comprises first relative positions of the UAV and of the at least one known- location target, associated with the first plurality of points, corresponding to second relative positions of the UAV and of the at least one other target, associated with the second plurality of points.

28. The method of any one of claims 1 to 27, wherein coordinate axes of the at least one known-location target comprise at least one of a longitude, a latitude and an altitude.

29. The method of any one of claims 1 to 28, wherein the at least one calibration mission precedes the target-location mission.

30. The method of any one of claims 1 to 29, wherein the at least one calibration mission follows the target-location mission.

31. The method of any one of claims 1 to 30, wherein the at least one known-location target comprises a fixed-location target.

32. The method of the previous claim, wherein the fixed-location target comprises one of a ground structure, a tree, a road junction, and a street junction.

33. The method of the previous claim, wherein the ground structure is one of a building and a tower.

34. The method of any one of claims 32 to 33, wherein the first measured position information is associated with the base of the ground structure.

35. The method of any one of claims 1 to 34, wherein the known coordinates of the at least one known-location target are known to within a defined accuracy.

36. The method of any one of claims 17 to 19, further comprising: i) adjusting the second measured position information utilizing the correction data, thereby deriving corrected second measured position information associated with at least one second point of the second plurality of points.

37. The method of the previous claim, further comprising: j) outputting the corrected second measured position information to at least one external system.

38. The method of any one of claims 36 to 37, further comprising: k) determining the location information of the at least one other target, based on the corrected second measured position.

39. The method of any one of claims 1 to 38, wherein the first measured position information being indicative of one or more known first orientation angles of the at least one known-location target in one or more orientation directions, wherein the second measured position information being indicative of one or more second orientation angles of the other target in one or more orientation directions.

40. A method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data being indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data being indicative of coordinates of at least one known-location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, d) receiving, from the target-positioning system, second measurement data associated with the at least one sensor and with a target- location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and second plurality of points, orientations of the at least one sensor, meet a first similarity criterion, wherein the second measurement data being indicative of coordinates of the at least one other target, the coordinates constituting second measured position information; e) determining, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and f) adjusting the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

41. The method of the previous claim, further comprising: g) determining, based at least on the corrected second measurement data and on the second measured position information, the location information of the at least one other target.

42. A system configured to perform calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the system comprising a processing circuitry configured to: a) receive, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data being indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data being indicative of of at least one known- location target, the coordinates constituting first measured position information, b) receive known coordinates of the at least one known-location target, constituting known position information; and c) derive correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and in the second plurality of points, orientations of the at least one sensor, meet a first similarity criterion.

43. The system of claim 42, wherein the processing circuitry further configured to: d) receiving, from the target-positioning system, the second measurement data, the second measurement data being indicative of coordinates of the at least one other target, the coordinates constituting second measured position information.

44. The system of the previous claim, wherein the processing circuitry further configured to: e) determine, based at least on the correction data, a sensor error associated with the at least one sensor and with at least one second point of the second plurality of points; and f) adjust the second measurement data utilizing the sensor error, thereby deriving corrected second measurement data.

45. The system of the previous claim, wherein the processing circuitry further configured to: g) determine, based at least on the corrected second measurement data, the location information of the at least one other target.

46. The system any one of claims 42 to 45, wherein the target positioning calibration system is comprised in the UAV.

47. The system of any one of claims 42 to 46, wherein the target positioning calibration system is comprised in a ground station.

48. The UAV, comprising the system of any one of claims 42 to 47.

49. A non-transitory computer readable storage medium tangibly embodying a program of instructions that, when executed by a computer, cause the computer to perform a method of performing calibration of a target-positioning system of an Unmanned Aerial Vehicle (UAV), the method being performed by a processing circuitry and comprising:: a) receiving, from the target-positioning system, first measurement data, the first measurement data being associated with at least one calibration mission performed by the UAV, the first measurement data being indicative of measurements recorded, by at least one sensor of the UAV, at a first plurality of points, the first measurement data being indicative of coordinates of at least one known-location target, the coordinates constituting first measured position information, b) receiving known coordinates of the at least one known-location target, constituting known position information; and c) deriving correction data associated with each point of the first plurality of points, by comparing the first measured position information to the known position information, thereby enabling correction of second measurement data associated with the at least one sensor and with a target-location mission associated with the UAV, in a situation of fixed sensor inaccuracies, wherein the target-location mission is associated with determining location information of at least one other target, wherein the second measurement data is indicative of second measurements recorded, by the at least one sensor, at a second plurality of points, wherein for corresponding points in the first plurality of points and in the second plurality of points, orientations of the at least one sensor, meet a first similarity criterion.