GB2235293A

GB2235293A - Target information transmission system

Info

Publication number: GB2235293A
Application number: GB8919349A
Authority: GB
Inventors: Robert James Mcfarlane; Robert William Garioch
Original assignee: Ferranti International Signal PLC; GEC Ferranti Defence Systems Ltd
Current assignee: Ferranti International PLC; Leonardo UK Ltd
Priority date: 1989-08-25
Filing date: 1989-08-25
Publication date: 1991-02-27
Also published as: GB8919349D0; AU6291890A; CN1054157A; WO1991002988A1

Abstract

A system is provided which will transmit information concerning a target viewed by an observer (AC1) to a user system (AC2) possibly a second observer. The orientation of a sight-line from the observer to the target is determined relative to a first set of axes by angle-determining means (HMS1), and the position and attitude of the observer relative to a second set of axes is determined by first position-determining means (IRS1). Communication means (TX, RX) are provided to pass the angle, position and attitude information to the user system (AC2). The position and orientation of the user system relative to the second set of axes is determined by second position-determining means (IRS2). A data processor (DP) uses the information received from the communication means (TX, RX) and from the second position-determining means to determine the orientation of the target relative to the user system.

Description

TARGET INFORMATION TRANSMISSION SYSTEM It is frequently necessary in a combat situation for an observer of a target to be able to indicate the position of that target, at least approximately, to a data processing system and/or a second observer, referred to collectively in this specification as a "user system". In an air combat situation, for example, a pair of aircraft may be operating together on a patrol and a target may be viewed by the pilot of one of the aircraft. It is, of course, possible for the pilots to communicate by radio so that the information may be passed from one to the other by this means. This is not only time-consuming but also involves each pilot in some positive action at a time when they may already be busy with other things.A further problem arises in identifying the position or direction of the target. Vhilst the first pilot may be able to describe the bearing and elevation of the target relative to his own instantaneous heading, unless the second pilot is following the same course the information will have no relevance. Similarly, an estimation of range by one pilot will not be very accurate for the second pilot unless the two aircraft are close together.

It is an object of the present invention to provide a target information transmission system operable to transmit information concerning a target viewed by an observer to a user system with minimum involvement of the observer.

According to the present invention there is provided a target information transmission system operable to transmit information concerning a target viewed by an observer to a user system, which information transmission system includes angle-determining means for determining the orientation of an optical sightline between the observer and the target relative to a first system of axes, first position-determining means for determining the spatial position and attitude of the observer relative to a second system of axes, communication means for transmitting the said orientation position and attitude information to the user system, second position-determining means for determining the spatial position and attitude of the user system relative to the second system of axes, and signal processing means operable to determine the orientation of the target relative to user system.

In the case where the user system is a second observer the invention provides means for indicating to that second observer the orientation of a line of sight to the target relative to a third system of axes.

The Invention will now be described with reference to the accompanying drawing which is a schematic block diagram of an information transmission system according to an embodiment of the invention.

The embodiment to which the drawing relates envisages two aircraft each with a pilot wearing a helmet-mounted sight.

Basically this comprises a helmet having a partially-reflecting element onto which' an image of a sighting graticule is projected. The helmet is provided with sensors for determining its orientation relative to the aircraft cockpit so that the orientation of the line of sight from pilot to target may be determined relative to the axes of the aircraft. Many types of helmet-mounted sight are know, frequently using infra-red or electromagnetic radiation for sensing purposes. Such a sight forms the feature HMS1 of aircraft AC1 of the drawing. For the information defining the direction of that line of sight to be useful to anyone outside the aircraft it is necessary to relate it a different set of axes.This is done by using an inertial reference system IRKS1 to determine the spatial position of the aircraft and its attitude at the instant when the line of sight between-target and observer is defined. The information available therefore defines the direction of the line of sight relative to the aircraft axes and also the orientation of those axes and the instantaneous position of the aircraft relative to a spatial system of axes such as a latitude-longitude geometric system.

The information from the helmet-mounted sight and inertial navigation system may be suitably modified before being applied to a transmitter TX which conveys the information over a suitable communications channel in a suitable manner.

The second aircraft has a receiver RX which receives the transmitted information and passes it in a suitable form to a data processor DP. Also supplying an input to the data processor is an inertial reference system IRS2 which determines the spatial position and orientation of the second aircraft AC2, relative to the same spatial axes, that is the latitudelongitude axes, as aircraft AC1.

The data processor performs a series of coordinate transformations, firstly converting the line of sight direction from aircraft ACl into a direction relative to the latitudelongitude axes. ' This is then converted into a direction relative to the axes of the second aircraft AC2 using the signals from the inertial reference system IRS2. The data processor DP then supplies signals to the helmet-mounted sight HMS2 worn by the pilot of the second aircraft so that the projected display indicates to that pilot the direction of the target.

Coordinate transformation techniques are well-known and will not be described here. The technique used to indicate the line of sight direction to the second pilot may vary. It is possible, for example, to produce arrows in the pilot's field of view to indicate the quadrant or octant which he should scan to locate the target. It is also possible to produce a more precise aiming mark indicating target position. Bowever, since the target may well be moving rapidly on a possibly unknown course such a precise indication will be difficult. The helmet-mounted sight indication may be combined with non-visual indications. For example, if a target is behind the second aircraft it is possible to produce suitable sounds in the pilot's ears to indicate this, supplemented by the visual indication when he has changed direction so as to be able to see the target.

One factor that the system so far described has been unable to determine is range. It may be difficult for the first pilot to estimate the range of the target. However, a rough estimate may be obtained if the rate of rotation of the line of sight is measured as the observer changes position relative to the target.

The situation so far considered is that of two aircraft operating together. It will be clear that the same information transmission system may be used in other situations, possibly with some simplification. For example the pilot of a fixed or rotary wing aircraft may indicate the position of a target, either in the air or on the ground, to a ground-based observer, who may use the information to locate the target. Similarly both the observer and the "user system" may be ground-based.

Such a system may not require the use of an inertial reference system to determine position and the system of axes used may, for example, be a conventional map grid reference.

In an even simpler arrangement the observer and user may be the two-man crew of a single aircraft. The attitude and spatial position of the two are then the same, leaving only the line of sight direction to be conveyed from one to the other.

The nature of the communication channel and the associated transmitter and receiver has not been discussed.

Data will usually be transmitted in digital form and any suitable method of transmission may be used. This may be combined with or separate from any existing intercommunicating system.

The "user system" may of course be just that, having no human operator. Remote control of weapons or even simple information displays may be provided from the input provided by an observer.

Claims

Claims:

1. A target information transmission system operable to transmit information concerning a target viewed by an observer to a user system, which information transmission system includes angle-determining means for determining the orientation of an optical sight-line between the observer and the carget relative to a first system of axes, first position-determining means for determining the spatial position and attitude of the observer relative to a second system of axes, communication means for transmitting the said orientation, position and attitude information to the user system, second position-determining means for determining the spatial position and attitude of the user system relative to the second system of axes, and signal processing means operable to determine the orientation of the target relative to the user system.

2. A system as claimed in Claim 1 in which the angle-determining means includes a helmet-mounted sight having a helmet orientation system.

3. A system as claimed in either of Claims 1 or 2 in which the first position-determining means includes an inertial reference system.

4. A system as claimed in any one of Claims 1 to 3 in which the user system is a second observer located remote from the said observer and which includes means for indicating to said second observer the orientation of a line of sight to the target relative to a third system of axes.

5. A system as claimed in Claim 4 in which the indicating means include a helmet-mounted sight.

6. A system as claimed in any one of Claims 2 to 5 in which the second position-determining means includes an inertial reference system.

7. A target information transmission system substantially as herein described with reference to the accompanying drawing.