EP2240742A1

EP2240742A1 - Device and method for planning a surveillance mission on areas of interest that can be performed with a reconnoitring system using a reconnaissance aircraft

Info

Publication number: EP2240742A1
Application number: EP08751462A
Authority: EP
Inventors: Valerio Manetti
Original assignee: Selex Galileo SpA
Current assignee: Selex Galileo SpA
Priority date: 2008-01-21
Filing date: 2008-01-21
Publication date: 2010-10-20
Also published as: WO2009093276A1

Abstract

Described herein is a method for planning a surveillance mission of one or more areas via a reconnaissance aircraft (2), comprising the steps of : establishing (120) at least one first display constraint correlated to a state of visibility of the target within an area and at least one second display constraint correlated to the minimum dimension (DOmin) of the target in the area; determining (140) a set of main parameters correlated to the capacity of observation of the area and a set of secondary parameters correlated to the conditions of environmental visibility; calculating (210) 'a maximum threshold of observability (DMOC) of the target; and calculating a maximum reconnoitring distance (DMR) of the aircraft (2) as a function of the area in order to signal a condition of impossibility of planning of the surveillance mission when the maximum reconnoitring distance (DMR) and the maximum threshold of observability (DMOC) satisfy between them a first pre-set condition of observability.

Description

"DEVICE AND METHOD FOR PLANNING A SURVEILLANCE MISSION ON AREAS OF INTEREST THAT CAN BE PERFORMED WITH A RECONNOITRING SYSTEM USING A RECONNAISSANCE AIRCRAFT"

TECHNICAL FIELD

The present invention relates to a device and a method for planning a surveillance mission on areas of interest with a reconnoitring system using a reconnaissance aircraft.

BACKGROUND ART

As is known, reconnoitring systems have the function of identifying the presence of targets of interest of a civil or military nature potentially present within pre-set areas of a territory.

The reconnoitring systems cited above typically comprise a unmanned reconnaissance aircraft, typically referred to as UAV

(Unmanned Aerial Vehicle) , an image-acquisition device provided with one or more telecameras mounted on board the reconnaissance aircraft for acquiring the images of the territory flown over thereby, and a remote surveillance station, which is in turn provided with: a control system, designed to pilot the reconnaissance aircraft according to a plan of flight; a communications system capable of transceiving signals/data to and from the reconnaissance aircraft in order to receive the images acquired by the telecamera; display devices, designed to display on a monitor the images of the territory filmed at a certain scrolling rate; and a control interface, through which an operator is able to remotely control the image-acquisition apparatus.

Carrying out of a surveillance mission by the reconnoitring systems of the type described above envisages a preventive step of "flight planning" , in which an operator identifies on a cartographic map the area or areas to be surveyed and establishes, on the basis of the areas identified, the flight paths that the aircraft will have to traverse during reconnoitring .

Normally, the aforesaid flight planning is established in a way altogether uncorrelated from and independent of the capacity of observation of the images by the system in the course of reconnoitring of the area by the aircraft. If on the one hand the preventive step of flight planning referred to above can prove advantageous from the standpoint of correct execution of the reconnoitring flight by the aircraft over the different areas, on the other hand it can prove altogether inadequate for correct and/or complete observation of the areas to be monitored.

It frequently happens in fact that, in the course of the reconnoitring envisaged by the plan of flight established beforehand, the system is not able to observe the areas to be monitored correctly and/or completely, consequently limiting the capacity of detection of the targets by the operator.

DISCLOSURE OF INVENTION

The aim of the present invention is consequently to provide a device and a method that will enable planning of a surveillance mission according to the real capabilities of observation of the target by the reconnoitring system in the conditions of visibility encountered during reconnoitring, ensuring a complete observation of the areas, and that will be able to plan in an altogether automatic way the flight and observation path most suited to the areas to be observed.

Provided according to the present invention is a method for planning a surveillance mission that can be performed with a reconnoitring system using a reconnaissance aircraft, as specified in Claim 1 and preferably, but not necessarily, in any one of the claims that depend directly or indirectly upon Claim 1. Moreover provided according to the present invention is a device for planning a surveillance mission that can be performed with a -reconnoitring system using a reconnaissance aircraft, as specified in Claim 28.

Moreover provided according to the present invention is a computer, as specified in Claim 29.

Finally, provided according to the present invention is a software product as specified in Claim 30.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the annexed drawings, which illustrate a non- limiting example of embodiment thereof and in which:

Figure 1 is a schematic illustration of a reconnoitring system provided with a device for planning a surveillance mission over areas of interest made according to the teachings of the present invention;

- Figure 2 shows a flowchart of the operations implemented by the device shown in Figure 1 during planning of the surveillance mission;

- Figure 3 shows a flowchart of the operations implemented by the device shown in Figure 1 during a step of initialization of the parameters used for planning the surveillance mission;

- Figure 4 shows a flowchart of the operations implemented by the device shown in Figure 1 during a first planning strategy envisaged by the system shown in Figure 1; - Figure 5 shows a possible example of surveillance mission planned on a two-dimensional area of vast proportions envisaged by the first planning strategy;

Figure 6 shows a possible example of the surveillance mission planned on a two-dimensional area of vast proportions envisaged by a second planning strategy;

Figure 7 shows a possible example of the surveillance mission planned on a two-dimensional area of vast proportions in the absence of the stand-off constraint;

- Figure 8 shows a flowchart of the operations implemented by the device shown -in Figure 1 according to a third planning strategy;

- Figure 9 shows a possible example of a surveillance mission planned on a portion of territory having a substantially striplike shape;

Figures 10 and 11 show as many possible examples of surveillance mission planned on a two-dimensional area of limited proportions; and

- Figure 12 is a possible example of the overall planned surveillance mission.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, the reference number 1 designates as a whole a reconnoitring system, which is able to identify one or more targets of a civil, military or similar nature, located within pre-set areas of interest of a given territory.

The reconnoitring system 1 basically comprises a reconnaissance aircraft 2, and an image-acquisition apparatus 3, which is preferably, but not necessarily, provided with a photographic camera or telecamera 3a operating in the range of the visible and/or of the infrared, which is provided with one or more electro-optical sensors and an optical system (not illustrated) and is mounted on the aircraft 2 with its own pointing axis, that can be oriented freely in the space so as to enable acquisition of the images of the underlying territory, and a mechanical positioning member 3b, which is designed, upon command, to move the telecamera 3a with respect to the aircraft 2 in order to vary the angles of pointing thereof .

It should be pointed out that the aircraft 2 can be preferably, but not necessarily, a UAV or else a manned aircraft, equipped with a flight control system (FCS) , which will enable automatic execution of pointing of the electro- optical sensors and/or automatic execution of the flight according to plan.-

The reconnoitring system 1 moreover comprises an apparatus 4, for example a GPS (Global Positioning System) receiver, preferably coupled to an inertial navigator (known and not illustrated herein) , which has the function of detecting, instant by instant, both the position of the aircraft 2 in space with respect to a spatial reference system, which in the examples shown in attached figures is of a cartesian type X, Y, Z, and the roll and pitch attitudes and the orientation with respect to the geographical North of the bow of the aircraft 2.

The reconnoitring system 1 moreover comprises an on-board computer 2a, designed for performing automatically the surveillance mission programmed, and a remote surveillance station 5, which is provided with: a control system 5a, designed to pilot the reconnaissance aircraft 2 according to a given flight plan; a communications system 5b able to carrying out transceiving signals/data to and from the aircraft 2 in order to receive the images acquired from the telecamera or telecameras 3a; and a display device 5c provided, for example, with a monitor designed to display the images of the territory acquired by the telecamera 3a.

The image-acquisition apparatus 3, the on-board computer 2a, the apparatus 4, the control system 5a, the communications system 5b, and the display device 5c are apparatuses that are known and will consequently not be described any further herein.

Unlike reconnoitring systems of a known type, the reconnoitring system 1 moreover comprises a computing device 10, which is able to signal the possibility or impossibility of planning a surveillance mission according to the real capabilities of observation of the target by the reconnoitring system in the conditions of visibility envisaged during reconnoitring and, if so, plans the surveillance mission itself in an altogether automatic way, without, that is, the aid of a direct programming performed by an operator.

In particular, the computing device 10 is able to implement a method that plans, i.e., programs, the surveillance mission of the aircraft 2, on the basis of the characteristics of the target and/or on the basis of the areas of interest to be monitored, and/or on the basis of a set of environmental parameters, such as visibility, temperature, atmospheric pressure, and/or on the basis of the lighting conditions, and/or according to a set of parameters that characterize the image-acquisition apparatus 3.

In detail, the surveillance mission basically comprises an "overall" plan of flight of the aircraft 2, and a "overall" plan of observation of the territory that can be carried out through the apparatus 3, in the course of execution of the flight by the aircraft 2.

From what has been described above it should be noted that the overall flight plan corresponds to the flight that the aircraft 2 performs in the course of the entire surveillance mission and is characterized by one or more "local" flight plans, each of which comprises, in turn, one or more flight paths that the aircraft 2 must traverse during surveillance of a corresponding area. Each local flight plan is moreover characterized by: a speed of advance of the aircraft 2 over the area,- a minimum reconnoitring height that the aircraft 2 must keep to with respect to the territory/area to be observed; and preferably, but not necessarily, one or more states of standby of the aircraft 2, each of which is performed by the aircraft 2 traversing a circular standby- orbit centred in a point located along the flight path envisaged by the local flight plan.

As regards, instead, the overall observation plan, this represents the set of the scans that the apparatus 3 must perform during the entire mission of surveillance of the areas and comprises one or more local observation plans, each of which is characterized by a scanning path constituted by a series of segments of scanning of an area, by a total number of samplings, i.e., by a number of image acquisitions to be carried out necessarily on each area for enabling a complete display of the entire area under observation, and by the dimensions of the portions of area of the territory that can be represented in each image sampled.

According to the information indicated above and to the local flight plan envisaged, the method defines the "local" observation path and hence determines the displacements to be imparted on the telecamera 3a in space during motion of the aircraft 2 so that the optical axis of the telecamera 3a itself will intersect the territory along the scanning path determined, and at the same time determines the angular opening to be set, instant by instant, on the optical system of the telecamera 3a itself so that the image acquired thereby will contain a portion of territory having the dimensions envisaged.

With reference to Figure 1, the computing device 10 moreover comprises a processing unit 11 designed to implement the method for planning the surveillance mission, and an interface unit 12 through which an operator can supply data and/or information to the processing unit 11. In the case in point, the processing unit 11 can comprise a computer or any other similar electronic device able to process appropriately the information according to the method for planning the surveillance mission described hereinafter, whereas the interface unit 12 can be defined, for example, by a control keypad, and/or by a mouse or any other device that will enable an operator to .interact with and issue commands to the processing unit 11.

With reference to Figures 2-12, described hereinafter is the method for planning the surveillance mission that can be implemented by the processing unit 11.

With reference to Figures 2 and 3, the method for planning the surveillance mission envisages an initialization step (block 100), during which the processing unit 11 receives at input: a set of parameters that characterize the type or types of the area or areas to be observed; for each area, a set of parameters that characterize the target to be sought/surveyed; a set of parameters that characterize the optical system and/or the electro-optical sensors of the telecamera 3a; and a set of parameters that characterize the conditions of environmental visibility.

The method for planning the surveillance mission moreover comprises a processing/calculation step (block 200) , in which the processing unit 11 determines the overall flight plan and the overall observation plan and carries out a final check of the plans determined according to the modalities described in detail hereinafter. In the case in point, for each area to be monitored, the method processes the parameters referred to above to determine the corresponding optimal local observation plan and the optimal local flight plan associated to the area to be surveyed itself.

With reference to Figure 3, the planning-initialization step of the method (block 100 in Figure 2) basically envisages the following steps: a step of definition of the areas to be reconnoitred (block 110) ; for each area to be surveyed, a step of definition of the characteristics of the target to be surveyed/sought within the area itself (block 120) ; a step of definition of the flight constraints of the aircraft 2 (block 130) ; a step of definition of first parameters correlated to the characteristics of the optical system and/or of the electro-optical sensors of the telecamera 3a (block 140) ; a step of definition of second parameters correlated to the environmental conditions (block 150) ; and a step of definition of a constraint correlated to the minimum contrast of the images acquired by the telecamera 3a that can be displayed by the display devices 5c (block 160) .

In particular, with reference to the example shown in Figure 3, the step of definition of the areas to be reconnoitred (block 110) comprises the step of delimiting the perimeter of each area to be observed on a digital map displayed, for example, through the monitor of the display devices 5c. The delimitation of each area can be carried out by the operator by drawing on the digital map itself a selection frame of a rectangular, or square, or else circular shape, containing the area within which observation for detection of the potential target is required.

On the basis of each area selected, the method establishes the dimensions of the area to be surveyed, a "preliminary" local- scanning-path model, and a "preliminary" local-flight-path model, and, according to the parameters set during the initialization step, characterizes for each area the local- flight-path model and the local-scanning-path model optimized for the area to be surveyed.

In the case in point, the areas to be surveyed envisaged by the method can be divided basically into the following three categories: two-dimensional surface portions which can be delimited on the digital map by selecting a frame of a rectangular or square shape,- strips of small width having an elongated shape and associated, for example, to stretches of roads, and/or coasts, and/or state boundaries, which can be delimited on the digital map with a broken line that can be superimposed on the strip and has a width substantially equal to the strip itself; and point elements of known co-ordinates, which can be delimited by the operator on the digital map using a circular frame centred in the point element itself. The two-dimensional surface portions can moreover, in turn, be divided according to their dimensions, into "vast" two- dimensional surface portions and "limited" two-dimensional surface portions .

The step of definition of the areas (block 110) moreover comprises: the steps of establishing the sequential order of observation of the areas selected during the flight; for each area selected, the step of defining a point of start-of- reconnoitring WPVi positioned preferably, but not necessarily, in a point corresponding to a first vertex of the selection frame, and a point of end-of-reconnoitring WPVfi positioned preferably, but not necessarily, in a point corresponding to an opposite vertex of the selection frame.

Finally, the step of definition of the areas (block 110) comprises the step of establishing a maximum time of observation of each area TMax.

As regards, instead, the step of definition of the constraints correlated to the characteristics of the target (block 120) , it comprises the steps of establishing: the minimum dimensions of the target DOmin in terms of width and length; a value indicating the percentage contrast of the target with respect to the terrain, in the case where the telecamera 3a operates in the range of the visible, and/or a value indicating the minimum difference of temperature DTmin of the target, in the case where the telecamera 3a operates in the range of the infrared; an index of observability Io of the target consisting in the minimum time of scrolling of the image that enables a sufficient permanence of the target on the monitor in order to enable display/reconnoitring of the target and its analysis in real t-ime by the operator.

As regards the step of definition of the constraints of the surveillance mission (block 130) , this comprises the step of establishing preliminarily for each area selected: a minimum reconnoitring height hv of the aircraft 2 envisaged in each area to be reconnoitred with respect to the ground; the minimum speed Vm that the aircraft 2 can maintain over the area; the radius R of each circular standby orbit that will be described by the aircraft 2 along a flight path during reconnoitring of an area in the case of standby; the co- ordinates and orientation of the runways PIST for take-off and/or landing of the aircraft 2 envisaged in the surveillance mission; the flight path TPIST followed by the aircraft in the course of take-off and the flight path followed by the aircraft in the course of landing; the height of flight of the aircraft 2 at the end of take-off and the height of flight of the aircraft 2 at start of landing; the wind conditions on the ground, in an area corresponding to the take-off and landing runways PIST, and the wind conditions at the reconnoitring height hv.

The constraints of the surveillance mission can moreover comprise an indication on the presence or otherwise of a stand-off constraint. In the case in point, the stand-off constraint imposes a distance, designated hereinafter by Dso, that the aircraft 2 will have to maintain during observation of an area with respect to the perimeter of the surveyed area itself.

As regards the step of definition of the characteristics of the telecamera or telecameras 3a (block 140) , this comprises the step of defining a transfer function of the optical/electronic system and/or of the electro-optical sensors of the telecamera 3a, and the minimum/maximum field of view associated to the telecamera or telecameras 3a. It should be pointed out that the method is able to determine the transfer function of the optical/electronic system and/or of the electro-optical sensors of the telecamera 3a by applying a calculation algorithm of a known type and consequently not described in detail .

As regards the step of defining the conditions of environmental visibility (block 150) , this comprises the step of receiving a set of data correlated to the environmental visibility in order to define a transfer function of the atmosphere in the area to be monitored. The transfer function of the atmosphere can be determined in the range of frequencies of light comprised in the IR and/or visible spectrum and/or laser spectrum.

It should be pointed out that the method is able to implement an algorithm of a known type that calculates the transfer function of the atmosphere on the basis of the visibility, and/or of the season, and/or of the time, and/or of the meteorological situation corresponding to a state of clear sky, or a state of overcast sky or a state of rain, and/or according to the relative humidity, temperature, wind speed, and/or the type of atmospheric aerosol in an area corresponding to agricultural terrains, desert terrains, lakes, centres of population, industrial estates, wooded areas, etc.

With reference to Figure 2, the processing step (block 200) comprises the step of calculating for each area to be surveyed selected by the operator, a maximum threshold of theoretical observability referred to hereinafter as "maximum allowed distance of observation DMOC" of the aircraft 2 with respect to the target (block 210) . The maximum threshold of theoretical observability, i.e., the maximum allowed distance of observation DMOC, consists in the distance that the- aircraft 2 must keep from the target for guaranteeing that the operator has a sufficient view of the target represented in the images acquired by the telecamera 3a and displayed by the monitor. In other words, the observation of the target at a distance greater than the maximum threshold of theoretical observability, i.e., the maximum allowed distance of observation DMOC, would entail a view that is potentially insufficient or degraded of the target itself by an operator.

In detail, the maximum threshold of theoretical observability, i.e., the maximum allowed distance of observation DMOC, is calculated by the method through a calculation algorithm according to the following parameters: the minimum dimension of the target DOmin, the meteorological conditions, the transfer function of the optical/electronic system and of the electro-optical sensor of the telecamera 3a, the minimum/maximum field of view associated to the telecamera 3a; the transfer function of the atmosphere; and the minimum contrast set by the operator.

In detail, the algorithm for calculation of the maximum allowed distance of observation DMOC can be contained in a known program, such as, for example, the program known as EOTDA (electro-optic tactical decision aid) , or the program known as LOWTRAN 6/7, or else the program known as MODTRAN. Said algorithm is known and consequently will not be described any further .

The processing step (block 200) moreover comprises the step of recognizing for each area the type of area selected (block 220) . In the case in point, recognition of the area can be carried out by the method on the basis of the dimensions and/or shape of the selection frame that delimits the area. For example, if the length and the width of the selection frame are greater than two pre-set maximum thresholds, the method can recognize a vast two-dimensional area; if the length and the width of the selection frame are smaller than the two pre-set maximum thresholds, but greater than two pre-set intermediate thresholds, the method can recognize a limited two-dimensional area,- if, instead, the width of the frame is smaller than a pre-set minimum threshold but the length is greater than the pre-set maximum threshold, the method can recognize a strip; and, finally, if the width and the length of the frame are both smaller than two pre-set minimum thresholds, the method can recognize a point element.

In the case where the selected area corresponds to a vast two- dimensional surface portion (block 230 in Figure 2), the method checks the presence or otherwise of the stand-off constraint (block 240) . In the case where the stand-off constraint is present, and hence the stand-off distance Dso is other than zero (output YES from block 240) , the method calculates a maximum possible reconnoitring distance DMR of the aircraft 2 with respect to the target (block 250) .

It should be pointed out that, in the example shown in Figure 5, the vast two-dimensional area is delimited by a selection frame 26 of a rectangular shape having a longitudinal axis AL set parallel to the cartesian axis Y, and in which the two major sides of the frame 26 are parallel to the longitudinal axis AL and have a length L, whereas the two minor sides thereof are transverse to the longitudinal axis AL and have a length H. In this step, the method makes a first preliminary- check of observability (block 250 in Figure 2) , which envisages comparing a maximum possible reconnoitring distance DMR with the maximum allowed distance of observation DMOC (block 260) , and checks the following first condition of observability: a) DMR>DMOC, where the maximum reconnoitring distance is calculated as If this condition is not satisfied, the method checks one of the following second conditions of observability: bl) DMR<=DMOC, where the maximum reconnoitring distance is calculated as DMR = K^( (D_so + 2R + H / 2)² + hv²) ; or b2) DMR<=DM0C, where the maximum reconnoitring distance is calculated as DMR = where K is a pre-set constant equal to approximately 1.3.

In the case where the aforesaid second condition of observability b2) is satisfied, the method determines that the constraints imposed in the initialization step are acceptable, i.e., that the area to be monitored is altogether observable via a surveillance mission defined by a first planning strategy (block 270) described in detail hereinafter.

If, in the course of the first preliminary check of observability (block 260) , the second condition of observability bl) is instead satisfied, the method determines that the constraints imposed in the initialization step are acceptable, i.e., that the area can be observed via a surveillance mission defined by a second planning strategy (block 280) described in detail hereinafter.

If, instead, in the course of the first check of observability (block 260) the first condition of observability a) is satisfied, i.e., DMR>DMOC, then the method signals that the area is not completely observable and that it is not possible to plan an adequate local observation plan and a corresponding local flight plan (block 290) . In this case, the method indicates to the operator the need to change some constraints imposed in the initialization step. Said change can envisage: a reduction in the stand-off distance Dso; and/or a reduction in the radius R of the standby orbits; and/or an increase in the minimum contrast accepted; and/or an increase in the minimum dimensions DOmin of the target; and/or a reduction in the dimensions of -the area to be reconnoitred.

Following upon the new setting of the parameters, the method repeats the calculation of the maximum possible reconnoitring distance DMR (block 250) , implements the first check of observability envisaged by block 260 and, according to the result of the check, defines the flight planning strategy envisaged.

With reference to Figures 2, 4 and 5, the first planning strategy (block 270) envisages a local-flight-path model associated to the type of area recognized (block 500) . In the case of a vast two-dimensional area with a stand-off constraint, the first planning strategy envisages a flight path 22 located outside of the area itself (Figure 5) .

In particular, with reference to Figures 4 and 5, the method envisages that the local-flight-path model comprises a local flight path 22 set parallel to the longitudinal axis AL and facing a major side of the frame 26 at a distance Dso. In this case, the local-flight-path model selected automatically by the method can envisage, along the flight path 22, a number of circular standby orbits 23 of the aircraft 2, each of which is associated to a standby time corresponding to the time of scanning of the area by the telecamera 3a, and is characterized by the radius R, and by a centre Cti (with i ranging between 1 and Nl) positioned along the flight path 22 itself (block 500 in Figure 4) .

In this case, the method moreover identifies a local-scanning- path model associated to the area recognized (block 500) , comprising a series of transverse scanning stretches 24 that develop in a direction transverse to the longitudinal axis AL within the area and are set at a distance apart from one another, and a series of longitudinal scanning stretches 25, which develop within the area in a direction parallel to the longitudinal axis- AL. In the case in point, the transverse scanning stretches 24 and longitudinal scanning stretches 25 of the observation plan are set at intervals apart from one another in such a way as to form within the frame 26 a scanning path that is substantially fret-shaped. In greater detail, the fret of the observation plan comprises a series of semi-portions of scanning lines, each of which comprises a transverse scanning stretch 24 and a consecutive longitudinal scanning stretch 25.

With reference to Figures 4 and 5, the flight plan and the observation plan identified are adapted by the method to the area to be surveyed through the calculation of a series of calculation factors, such as the transverse dimensions of the field of view hi and the longitudinal dimensions Ii thereof, and the number Nsp of semi-portions included in the observation plan. In the case in point, the number Nsp of semi-portions is given by the following relation: Nsp=Int( (L- (1-Ot) *hi)/SLp+0.5) (block 510); where: Int (x) is the function that calculates the integer part of x; Ot is a numeric value comprised between 0 and 1 correlated to the superposition between two images acquired by the telecamera 3a in two consecutive instants; hi is the width of the image on the ground; and SLp corresponds to a preliminary length of a longitudinal scanning stretch 25 calculated applying the relation SLp=hi* (1-Ot) .

At this point, the method calculates the total length SLd of the longitudinal scanning stretch 25 applying the relation SLd= (L- (1-Ot) *hi) /Nsp (block 520).

Next, the method calculates a preliminary total time Tstp of scanning of the area by applying the following relation: Tstp=( (Nsp+1) *ST+Nsp*SLd) /Vsp (block 530), where Vsp is to a preliminary speed of scan of the territory calculated applying the relation Vsp=hi/Io, and ST is the transverse width of the scan, which can be calculated applying the relation ST=H-Ii* (1-Ot) , where Ii is the width of the image filmed by the telecamera 3a on the ground.

Next, the method calculates the average speed Vmv of the aircraft 2 along the major side of the area during scanning of the area itself applying the relation Vmv= (L- (1-Ot) *hi) /Tstp (block 540) .

Next, the method checks whether the average speed Vmv of the aircraft 2 is higher than or equal to the minimum speed Vm of the aircraft 2 applying the relation Vm<Vmv or Vm=Vmv (block 550) .

If it is (output YES from block 550), i.e., if the minimum speed Vm of the aircraft 2 is smaller than or equal to the average speed Vmv of the aircraft 2, the method determines the total time of scanning of the area Tstt applying the relation Tstt=(L-(l-Ot) *hi) /Vm (block 560) and calculates the definitive scanning speed Vsd of the territory in the way described next (block 610) .

If it is not (output NO from block 550) , the method calculates a preliminary step Dpp between the standby orbits of the aircraft 2 applying the relation Dpp=2pR*Vmv/ (Vm-Vmv) (block 570).

At this point the method calculates the number of standby orbits Nl of the aircraft 2 applying the relation Nl=Int( ( (L-I-Ot) *hi) /Dpp) (block 580).

Next, the method calculates: the definitive step Dpd between the standby orbits applying the relation Dpd= (L- (1-Ot) *hi) /Nl (block 590) , and the definitive total time Tstt of scanning of the area applying the relation Tstt= (Nl* (Dpd+2pR) ) /Vm (block 600) .

Next, the method calculates the definitive speed Vsd of scan of the territory applying the relation Vsd=Tst*Vs/Tstt (block 610) .

At this point, the method is able to configure the flight plan (block 620) on the digital map with respect to a cartesian reference system X, Y having origin in the point of start-of- reconnoitring WPVi i=l and oriented along the sides of the frame 26 including the area to be surveyed.

In particular, the method defines the flight path assigning: to a point of start-of-reconnoitring WPVi (Xpvi, Ypvi) i=l of the flight path 22 the co-ordinates Xpvi=-Dso; Ypvi=0; to a point of end-of-reconnoitring WPVfi (Xpvfi, Ypvfi) of the flight path 22 the co-ordinates Xpvfi=-Dso; Ypvfi=L; to a point WPSi (Xpsi, Ypsi) of the flight path 22 in which the apparatus 3 starts scanning of the area and i=l the co-ordinates Xpsi=-Dso; Ypsi=hi* (1-Ot) /2; and to a point WPSfi (Xpsfi, Ypsfi) of the stretch in which the apparatus 3 terminates scanning of the area the co-ordinates XPSfi=-Dso; YPSfi=L-hi* (1-Ot) /2.

The method moreover assigns to the local flight plan the number of standby orbits of the aircraft Nl and calculates the centres Cti(Xci,Yci) applying the relations: Xcti=- (Dso+R) ; Ycti=hi* (1-Ot) /2+Dp* (2i-l) /2 (where i is comprised between 1 to Nl) .

Finally, the method assigns to the speed of the aircraft 2 over the area the value Vm and to the height the value sl=hv.

Following upon configuration of the flight plan, the method defines the scanning-path model (block 630) shaped like a Greek fret with a number of scans Nsp. In particular, the scanning-path model comprises a plurality of transverse scanning stretches 24 joined together by as many longitudinal scanning stretches 25 in positions corresponding to a set of points Psj (with j comprised between 1 and 2*Nsp) .

In greater detail, the method configures the scanning-path model by defining the points Psj that join the transverse scanning stretches 24 and longitudinal scanning stretches 25. In the case in point, the method envisages calculating, cyclically, the points Psj (Xsj , Ysj , Zsj ) (with j ranging between 1 and 2*Nps) as follows: XsJ=I* (l-0t)/2+(l+(-l)nx) *ST/2; Ysj=h (1-Ot) /2+ny* (SL-I) ; where nx=Int (j/2) +1 and ny=Int ( (j+1) /2) .

As regards, instead, the third component ZSj of each point, this corresponds preferably, but not necessarily, to the height from ground and is given by the method according to the information contained on the digital cartographic map in a region corresponding to the points of co-ordinates Xsj and Ysj .

With reference to Figures 2 and 6, the second planning strategy (block 280) envisages dividing the area to be observed into at least two distinct sub-areas 27' and 27'' (as shown in Figure 6) , divided from one another by a midplane orthogonal to the area itself. In this case, the method configures for each sub-area 27' and 27'' the flight plan and the observation plan, implementing the same operations implemented by blocks 500-630 described above. It is evident that in this case the flight path comprises two paths 22' and 22'' having respective circular standby orbits 23' and 23''. The paths 22' and 22'' are external to the respective sub- areas 27' and 27'' and are radiused to one another by an intermediate stretch (not illustrated) having the shape of a semi-circle of radius R=Dso+H/2 with the two ends connected respectively to the paths 22' and 22'' in the points WPfi and WPVi.

With reference to Figure 2, in the case of absence of the stand-off constraint (output NO from block 240) , the method envisages carrying out the steps described in what follows . It calculates a preliminary scanning speed Vsp=hi/Io and compares Vsp with the minimum speed Vm of flight. If the minimum speed Vm of flight is greater than the preliminary scanning speed Vsp, the method assigns to ST a value zero, ST=O, whilst if the minimum speed Vm of flight is lower than or equal to the preliminary scanning speed Vsp, the method calculates the length ST of the transverse scan 24 as follows: ST=SL* (Vsp-Vm) /Vm. At this point, the method calculates the width of the observation band As of the area applying the relation As=hi+ST.

Now, the method makes a second check of observability (block 245) calculating the maximum distance of observation possible DMR of the area through the following relation:

DMR = κV( (As / 2)² + hv²) , where K=I .3.

The second check of observability of the method envisages comparing the maximum possible reconnoitring distance DMR with the maximum allowed distance of observation DMOC by applying the inequality DMR<=DM0C. If the method finds that the first condition of observability DMR>DMOC is satisfied, then the area is not completely observable. In this case, the method identifies a state of impossibility of planning of a local observation plan and of a corresponding flight plan that will be able to 'satisfy the pre-set constraints, and signals to the operator the need to change the constraints themselves set in the initialization step. Said change can envisage a reduction in the height hv.

If, instead, the second condition of observability DMR<=DMOC is satisfied, the method determines that the constraints imposed in the initialization step are acceptable, i.e., that the area is entirely observable via a surveillance mission.

At this point, the method implements a third planning strategy (block 300) comprising a local-flight-path model without standby orbits (Figure I)₁ which envisages: dividing the area into a series of sub-areas 27', 27'', and 27''' (three of which are shown in the example of Figure 7) having preferably, but not necessarily, the same dimensions,- and tracing the flight paths 22 in a direction coinciding with the longitudinal axis ALi (with i comprised between 1 and the number of sub-areas) of each sub-area 27', 27'', and 27'''.

With reference to Figures 7 and 8, the method envisages configuration of the observation plan implementing for each sub-area 27', 27'' and 27''' to be observed the steps outlined in what follows.

Initially (Figure 8) , a preliminary scanning speed Vsp=hi/Io (block 700) is calculated, which is then compared with the minimum speed Vm of flight (block 710) .

If the minimum speed Vm of flight is higher than the preliminary scanning speed Vsp (output NO from block 710) , the method assigns to ST a zero value, ST=O (block 720) . If, instead, the minimum speed Vm of flight is lower than or equal to the preliminary scanning speed Vsp (output YES from block 710) , the method calculates the length ST of the transverse scan 24 as follows: ST=SL* (Vsp-Vm) /Vm (block 730).

At this point, the method calculates the width of the observation band As of the sub-area (for example, the sub-area 27') applying the relation As=hi+ST (block 740).

Next, the method calculates the number of paths Nl of the local-flight-plan model and the distance DL between the paths themselves along the longitudinal axes ALi (with i comprised between 1 and the number of sub-areas) of the respective sub- areas 27', 27-'' and 27''' applying the relation Nl=Int (H/ (As* (1-Ot) ) and DL=H/Nl (block 750).

It should be pointed out that the method can envisage increasing, preferably, but not necessarily, by one unit the number of paths Nl according to the relative position between the entry point WPVi and the end point WPVfi of the flight plan envisaged. In the case in point, if WPVi and WPVfi face one and the same side of the area to be reconnoitred, Nl will be calculated in such a way as to be even, whereas, otherwise, i.e., if WPVi and WPVfi face the opposite sides of the area to be reconnoitred, Nl will be calculated in such a way as to be odd. Consequently, the method is able to decide each time whether to add or not a unit value to the number of paths Nl calculated in block 750 according to the mutual position of the two points of start and end of the flight path envisaged with respect to the sub-area to be observed.

Next, the method calculates the number Nsp of semi-portions applying the relationNsp=Int (1+ (L-I* (1-Ot) /SL) ) (block 760).

At this point, the method envisages calculating the total scanning time Tsc associated to each flight path of a sub-area 27' and/or 27'' and/or 27''' applying the relation TSC=(L-I* (1-Ot) ) /Vm (block 770) .

Now, the method envisages calculating the length of the total longitudinal scanning stretch 25 of each sub-area 27' and/or 27'' and/or 27''' by applying the relation SLd=(L-I* (1-Ot) ) /Nsp (block 780).

Next, the method envisages calculating the definitive scanning speed Vsd= (Nsp* (ST+SLd) +ST) /Tsc (block 790). Once the aforesaid quantities have been determined, the method is able to define the flight plan and the local observation plan.

In detail, definition of the flight plan (block 792) envisages calculating cyclically, with i ranging between 1 and Nl: the co-ordinates of the point of start WPVi(XPVi₇YPVi) of each path 22 by applying the relation XPVi= (hi* (1-Ot) +ST) /2+DL* (i- l)and YPVi=O (for i odd); or YPVi=L (for i even); the coordinates of the point of end-of-path WPVfi (XPVfi, YPVfi) by applying the relation XPVfi=XPVi,- YPVfi=L (for i odd), or alternatively YPVfi=0 (for i even) ; the co-ordinates of the point of start-of-scan WPSi (XPSi, YPSi) corresponding to XPSi= (hi* (1-Ot) +ST) /2+DL* (i-1) ; YPSi=Ii* (1-Ot) /2 (for i odd), or YPSi=L-I* (1-Ot) /2 (for i even).

The method moreover envisages determining the radius of the semi-circles 22b for radiusing the paths 22, which is equal to R=DL/2 and the co-ordinates XCi= (h* (1-Ot) +ST) /2 + DL*(2i-l)/2 and YCi=L (for i odd) ; 0 (for i even) of the centres of the semi-circles themselves. The method finally envisages establishing the speed of the aircraft Vm and the height sl=hv thereof .

As regards, instead, the definition of the observation plan (block 794), it envisages calculating cyclically, with i ranging between 1 and Nl, the co-ordinates of the scanning path.

Also in this case, the model of the scanning path has for each sub-area 27' and/or 27'' and/or 27''' a path shaped like a fret comprising a plurality of transverse scanning stretches 24 joined together by as many longitudinal scanning stretches 25 in positions corresponding to a series of points Psi,j, the number of which is equal to 2*Nsp-l. In greater detail, the method configures the scanning-path model by defining the points Psi,j that delimit the transverse scanning stretches 24 and longitudinal scanning stretches 25. In the case in point, the method envisages for each sub-area 27', 27'' and 27''' calculating in a cyclic way the points Psi, j (Xsij , Ysij , Zsij ) (with j ranging between 1 and 2*Nps, and i ranging between 1 and Nl) as follows: Xsij=hi* (1-Ot) /2+(1+(-I)¹¹*) *ST/2+DL* (i-1) ; Ysij= (Ii*.(1-Ot) /2+ny* (SL-I) ) (1+ (-1) ^<i+1) ) /2+ (L-Ii* (1-Ot) /2- ny* (SL-I)) (1+ ( -1) ⁽ⁱ⁾ ) /2 ; where nx=Int ( j /2) +1 and ny=Int ( ( j+1) /2) , whilst Zsij is the height of terrain detected on the cartographic map on the points of co-ordinates Xsij ; Ysij .

With reference to Figures 2 and 9, in the case where the selected area corresponds to a strip (block 800) , the method checks the presence or otherwise of the stand-off constraint (block 810) .

It should be specified that in this case the strip 40 to be observed (shown in Figure 9) is divided into a broken line made up of a series of segments 41, defined by a series of rectangles having each a reduced length L and width Hi, joined together in such a way as to have the ends at least partially overlapping so as to cover entirely the strip 40. The segments can have different widths Hi, and consequently one of the segments can have a width Hi=Himax greater than the widths of the other segments .

With reference to Figure 2, if there exists a stand-off constraint and hence Dso is other than zero (output YES from block 810) , the method envisages implementing a third observability check (block 815) and calculates the maximum reconnoitring distance DMR of the area by applying the relation DMR = KΛ/( (DSO + 2R + H)² + hv²) where K is a constant equal, for example, to 1.3.

At this point, the third preliminary observability check of the method envisages comparing the maximum possible reconnoitring distance DMR with the maximum allowed distance of observation DMOC by applying the condition DMR<=DMOC.

If the method verifies that the first condition of observability DMR>DM0C is satisfied, then the area is not completely observable. In this case, the method identifies a state of impossibility of planning a local observation plan and a corresponding flight plan able to meet the constraints imposed and signals to the operator the need to change some constraints set in the initialization step according to what is implemented in block 290 described above. Said change can envisage: a reduction in the stand-off distance; and/or a reduction in the radius R of the orbits; and/or an increase in the minimum contrast accepted; and/or an increase in the minimum dimensions DOmin of the target, and/or a reduction in the dimensions of the area to be reconnoitred.

If, instead, the second condition of observability DMR<=DMOC is verified, the method determines that the constraints imposed in the initialization step are acceptable, i.e., that the area is entirely observable via a surveillance mission. At this point, the method reiterates for each segment 41 the operations described in block 270 corresponding to the first planning strategy (block 820) .

However, in this case, unlike what is implemented in block 270, the flight paths 22 of each segment 41 are set parallel to the longitudinal axes ALi of the segments 41 at a distance from the major side of the segments 41 equal to (Dso+Hi/2) (with i comprised between 1 and the number of segments) . In this step, the method determines moreover, for each path 22, the point WPVfi of intersection of the path 22 itself with the subsequent path 22.

In detail, the -method determines the initial end point WPVi (XPVi, YPVi) of the first path 22 assigning the coordinates XPVi=XIspl+/- (Dso + Hl/2) ) and YPVi=YIspl, where XIspl and YIspl are the co-ordinates of the first segment of the broken line encountered during the flight.

The method moreover determines the end point WPVfi (XPVfi, YPVfi) of the last stretch, assigning the coordinates XPVfi=XFspn+/- (Dso+Hn/2) , whilst YPVfin= YFspn, where XFspn and YFspn are the co-ordinates of the end of the last (n-th) segment of the broken line, and Hn is the width of the segment of the n-th path.

As a function of the points WPVi and WPVfi determined above, the method moreover calculates the length Li_eg(i) of each path 22. At this point, the method is able to determine the average speed Vmv of the aircraft 2 as a function of the length Li_eg(i) of the paths 22. The method then calculates the number of standby orbits Nl according to the same modality of calculation implemented in block 270 and on the basis of the average speed Vmv (block 830) .

If no stand-off constraint has been imposed (output NO from block 810) , the method makes a comparison between the minimum speed Vm of flight and a preliminary scanning speed Vsp=hi/Io (block 840) .

If the minimum speed Vm of flight is higher than the preliminary scanning speed Vsp, the method assigns to the length ST of transverse scanning 24 a zero value ST=O. If, instead, the minimum speed Vm of flight is lower than or equal to the preliminary scanning speed Vsp, the method calculates ST as follows: ST=SL* (Vsp-Vm) /Vm .

At this point, the method calculates the width As of the band of transverse observation of the segment 41 by applying the relation As=hi+ST.

Following upon calculation of the observation band As, the method compares the latter with the transverse width Himax

(block 850) . In the case where the width of the observation band As is greater than the transverse width Himax (output YES from block 850) , the method assigns to the stand-off distance

Dos a pre-set minimum value, preferably, but not necessarily, equal to Himax/2 (block 860) .

At this point, the method envisages implementing a fourth observability check (block 865) and calculates the maximum reconnoitring distance DMR of the area by applying the relation DMR = KV(Dso + 2R + H)² + hv²) , where K is a constant of a value, for example, of 1.3.

The observability check of the method envisages comparing the maximum possible reconnoitring distance DMR with the maximum allowed distance of observation DMOC by applying the condition DMR<=DMOC. If the method verifies that the first condition of observability DMR>DMOC is true, then the area is not completely observable. In this case, the method identifies a state of impossibility of planning a local observation plan and a corresponding flight plan able to satisfy the constraints imposed and signals to the operator the need to change some constraints set in the initialization step (block 290) .

If, instead, the second condition of observability DMR<=DMOC is true, the method determines that the constraints imposed in the initialization step are acceptable, and plans the observation plan implementing the operations of block 270. Also in this case, the flight paths 22 of each segment 41 of the broken line, instead of being determined as indicated in block 270, are determined through the steps implemented in block 830 described above.

If, instead, the width of the observation band As is smaller than the transverse width Hi (output NO from block 850) then the method implements a fifth check of observability (block 885) and calculates the maximum reconnoitring distance DMR of the area by applying the relation DMR = KV(Hi max/ 2)² + hv².

If the method verifies that the first condition of observability DMR>DM0C is true, then the area is not completely observable. In this case, the method identifies a state of impossibility of planning a local observation plan and a corresponding flight plan able to satisfy the constraints imposed and signals to the operator the need to change some constraints set in the initialization step (block 290) .

If, instead, the second condition of observability DMR<=DMOC is true, the method determines that the constraints imposed in the initialization step are acceptable and plans the observation plan implementing the operations envisaged by block 280 described above. In particular, in this case, the flight paths 22 of each segment 41 of the broken line, instead of being external to the segments 41, coincide with the median lines, i.e., with the axes ALi of each segment 41 and divide the area covered by the segment 41 itself into two specular parts. In detail, in this case, the flight paths 22 of each segment 41 of the broken line, instead of being determined as indicated in block 280, are determined as follows: paths 22 sharing the longitudinal axes ALi of the segments 41 of the broken line are traced and the points of intersection of the paths 22 (block 880) are calculated. In particular, the point WPVfi of intersection between each path and the next path 22 represents the end of the first path 22 and the start of the following path 22. In detail, the point WPVi (XPVi, YPVi) of the initial end of the first path 22 will have the co-ordinates XPVi=XIspl and YPVi=YlSpI, where XIspl and YIspl are the co- ordinates of the first segment of the broken line encountered during the flight, and the end point WPVfi (XPVfi, YPVfi) of the last path will have co-ordinates XPVfi=XFspn whilst YPVfn= YFspn, where XFispn and YFispn are the co-ordinates of the end of the last segment (n-th) of the broken line.

With reference to Figures 2 and 10, in the case where the selected area corresponds to a limited two-dimensional area

(block 900) that is rectangular 26 (indicated in Figure 10 with a solid line) or square 26' (indicated with a dashed line) , the method implements a sixth check of observability (block 905) calculating the maximum reconnoitring distance DMR of the area by applying the relation DMR = KΛ/( (DSO + 2R + H)² + L² + hv²) , in ^"the case shown in Figure 10; or alternatively DMR = κV( (H / 2)² + (L + R)² + hv²), in the case shown in Figure 11 and where K=I.

If the method verifies that the first condition of observability DMR>DMOC is true, then the area is not completely observable. In this case, the method identifies a state of impossibility of planning a local observation plan and a corresponding flight plan able to satisfy the constraints imposed and signals to the operator the need to change some constraints set in the initialization step (block 290) .

If, instead, the second condition of observability DMR<=DMOC is satisfied, the method determines that the constraints imposed in the initialization step are acceptable, and selects a closed-flight-path model, which, in the case of the rectangular frame, comprises two rectilinear paths 22 parallel to the longitudinal axis AL of the area radiused to one another at the opposite ends by two semi-circles of radius R, whilst in the case of a square frame 26' it envisages a single circular path 22' of radius R (block 910) .

In the case in point, the flight path envisaged by the model can fall completely outside of the area to be reconnoitred in such a way that the two paths 22, or the path 22', face the same side of the selection frame 26 (Figure 10) or else faces each a respective side of the frame 26 on opposite sides of the midplane of the frame 26 itself in such a way as to contain the frame 26 itself (as shown in Figure 11) .

In greater detail, in the case where the two paths 22 and 22 face the same side of the frame 26 Figure 10, the first path 22a has: a point of start-of-reconnoitring WPVi (Xpvi, Ypvi) of the flight path 22 having co-ordinates Xpvi=-Dso,- Ypvi=0; and a point of end-of-reconnoitring WPVfi (Xpvf , Ypvf) of the flight path 22 having co-ordinates Xpvfi=-Dso; Ypvfi=L. The second path 22b has a point of start-of-reconnoitring WPVi (Xpvi, Ypvi) of the flight path 22 having co-ordinates Xpvi=- (Dso+2R) ; Ypvi=L; and a point of end-of-reconnoitring WPVfi (Xpvfi, Ypvfi) of the flight path 22 having co-ordinates Xpvfi=- (Dso+2R) ;Ypvfi=0, whilst the two semi-circles have a radius R and each of them radiuses the two ends of the two paths 22a and 22b.

In the case where the two paths 22 face the corresponding two major sides of the frame 26 (as shown in Figure 11) , the first path 22 has: a point of start-of-reconnoitring WPVi (Xpvi, Ypvi) of co-ordinates Xpvi=-Dso; Ypvi=0; and a point of end-of- reconnoitring WPVf (Xpvf , Ypvf) of co-ordinates Xpvf=-Dso; Ypvf=L; the second path 22b has: a point of start- of -reconnoitring WPVi (Xpvi, Ypvi) of co-ordinates Xpvi= (Dso+H) ; Ypvi=L; and a point of end-of-reconnoitring WPVf (Xpvf , Ypvf) of co-ordinates Xpvf= (Dso+H) ;Ypvf=0 ; whilst the two semi-circles have a radius R and each of them radiuses the two ends of the two paths 22a and 22b. In the case where the frame is square 26' , the path 22' is circular and is sized to contain inside it the frame 26' itself at a distance equal to Dso.

In this case, the method plans a fret-shaped observation plan in which the co-ordinates of the stretches of transverse scan 24 and longitudinal scan 25 and the respective points of intersection Psi are determined through the steps implemented in block 270.

It should be added that, in this step, the method is able to determine the point of exit of the aircraft from the flight path as a function of the maximum time of observation of each area TMax. In the case in point, the exit point can correspond to the point of tangency to the closed path of the straight line that passes through the first point WP of the next area when the maximum time of observation of each area TMax has elapsed.

In the case where the selected area corresponds to a point element (block 1000) , the method moreover selects a pre-set flight-path model associated to the point element itself, which can be defined preferably, but not necessarily, by a circular orbit, which can be centred on the element itself or else be located at a pre-set distance from the element, in the case where, for example, a stand-off distance is envisaged.

As regards the observation path it envisages intersecting the optical axis of the telecamera 3a with the target when the circular orbit is being followed by the aircraft 2.

Following upon determination of the local flight plans and of the local observation plans, the method implements the observability check (block 1005) and calculates the maximum reconnoitring distance DMR of the point area by applying the relation or else, in the case of absence of the stand-off constraint, by applying the second relation • where K =1.

If the method verifies that the first condition of observability DMR>DMOC is true, then the point element is not completely observable. In this case, the method identifies a state of impossibility of planning a local observation plan and a corresponding flight plan able to satisfy the constraints imposed and signals to the operator the need to change some constraints set in the initialization step (block 290) .

If, instead, the second condition of observability DMR<=DM0C is true, the method determines that the constraints imposed in the initialization step are acceptable and hence the method maintains the predefined flight path and scanning path (block 1010) .

Following upon completion of the processing of the scanning plans and of the local observation plans, the method processes them in such a way as to orient them according to a common reference system. In the case in point, in this step the local observation plans and the corresponding local flight plans calculated for each area with respect to a reference of local co-ordinates are repositioned on the points of the territory according to a common reference. Said processing can envisage that all the co-ordinates of the paths of the observation plan and of the flight plan will be recalculated, for example, via an operation of roto-translation (block 1020) .

At this point, the local flight plans set according to the same reference are radiused to one another via stretches 28 that connect the end of the local flight plan of an individual area to the start of the local flight plan of the next area (Figure 12) . In the case of the closed paths linked to the limited areas or to the orbits in a point, they are connected with the straight- line TU tangential to the flight plan that passes through the point WPVi of start of the flight plan associated to the next area. The first path 28 will connect the point WPVf of the end-of-runway path TPIST with the first point WPVi of the path 22 assigned to the first area, and the last path 28 will connect the point WPVfi of the last path 22 of the overall flight plan to the end point WPVi of the landing path TPIST (block 1030) .

Following upon definition of the overall flight and observation plan, the method envisages preferably, but not necessarily, performing automatically a series of final verifications (block 1040) such as, for example: calculation of the length of the overall flight plan; control of the residual autonomy of the aircraft according to the length of the overall flight plan; control of the total time of flight that has elapsed; minimum height from ground defined by the intersection of the overall flight plan with the salient elements of the territory present in the digital map; check of possible areas in the observation of the territory in the shade on account of the orography of the ground and of the angle of observation envisaged; possible interruptions in the line of radio communications due to the orographic impediments identified; contrast; and/or probability of discovery of the target defined as a function of the variable characteristics such as the distance and atmospheric characteristics. Finally, the method can supply information on the maximum distance whereby the contrast falls below the minimum values programmed .

The method makes these data available to the operator for each path 22 of flight envisaged in the overall flight plan planned. On the basis of these data, the operator can thus advantageously modify some initialization data such as the height, and/or the stand-off distance, and/or the target and activate again the method according to what has been described above. In this way, on the basis of the data processed, the method performs once again the calculation and reproposes a new plan to the operator .

The method hence conveniently makes available to the operator: the flight plan defined by the sequence of the paths 22 with corresponding height and speed that the aircraft will have to observe automatically; the observation plan defined by the sequence of scans with associated thereto the angular opening of the objective that the telecamera 3a will have to follow automatically; possible areas in which the contrast of the hypothetical target is lower than the minimum detectable value; possible residual areas of observation in the shade; residual autonomy at the end of the mission; and total flight time .

In the case where during the flight some of the meteorological conditions planned were to vary, the operator is advantageously able to carry out real-time updating of some data used in the initialization step in such a way as to enable the method to plan the flight plan and/or the observation plan again according to the new parameters.

The method described above is extremely advantageous in so far as it determines in an altogether automatic way both a plan of observation of the areas to be observed and a plan of flight for the reconnaissance aircraft according to the real capacity of observation of the target in the real conditions of visibility, thus ensuring full coverage of the observation area.

Finally, it is clear that modifications and variations can be made to the device and the method described and illustrated herein, without thereby departing from the scope of the present invention as defined in the annexed claims.

Claims

1. A method for planning a surveillance mission of one or more areas of a territory via a reconnaissance aircraft (2) , which is designed to acquire the images of said areas for transmitting them to a remote surveillance station (5) , which processes said images for detecting the presence/absence of targets within the areas observed; said aircraft (2) comprising image-acquisition means (3), designed to carry out a scan of each of said areas to be observed according to a scanning path, and control means (2a) (5a) , designed to pilot said aircraft (2) according to a flight path; said remote surveillance station (5) comprising display means (5c) , designed to display a digital cartographic map representing said territory, control means (12) , designed to enable an operator to select one or more areas to be observed on said digital map, and processing means (11) , designed to plan said surveillance mission comprising a flight plan containing a flight path and an observation plan containing a scanning path; said method being characterized in that it comprises the steps of : a) detecting (110) on said digital map one or more selection frames (26) (26') (41) traced by the operator via said control means (12) and each containing an area to be observed; b) establishing (120) at least one first display constraint correlated to a state of minimum visibility of the target fixed by the operator via said control means (12) and representable in the image during display of the image itself through said display means (5c) ; c) establishing (120) at least one second display constraint correlated to the minimum dimension (DOmin) of the target fixed by the operator via said control means (12) and representable within the image during display of the image itself through said display means (5c) ; d) determining (140) a set of main parameters correlated to the capacity of observation of said areas by said acquisition means (3), and/or to the capacity of acquisition of the image of the areas themselves by said acquisition means (3) ; e) determining (150) a set of secondary parameters correlated to the conditions . of environmental visibility present in said areas ; for each of said areas selected on said digital map said method comprising the following steps: f) calculating (210) a maximum threshold of observability (DMOC) of said target by said acquisition means (3) as a function of said main and/or secondary parameters; said maximum threshold of observability (DMOC) corresponding to the maximum distance of positioning of said acquisition means (3) with respect to said area, beyond which the representation of said target in said image does not satisfy said first and/or second constraint; g) calculating (250) (260) (815) (865) (885) (905) (1005) a maximum reconnoitring distance (DMR) of the aircraft (2) from said area according to the area itself; and h) signalling a condition of impossibility of planning of said surveillance mission when said maximum reconnoitring distance (DMR) and said maximum threshold of observability (DMOC) satisfy between them a first pre-set condition of observability.

2. The method according to Claim 1, wherein said first condition of observability is satisfied when said maximum reconnoitring distance (DMR) is greater than said maximum threshold of observability (DMOC) DMR>DMOC.

3. The method according to Claim 1 or Claim 2, comprising the step i) of detecting a condition of possible planning of said surveillance mission when said maximum reconnoitring distance (DMR) and said maximum threshold of observability (DMOC) satisfy between them a second condition of observability corresponding to DMR<=DMOC.

4. The method according to any one of the preceding claims, comprising the step of establishing a first surveillance strategy provided with a flight path that comprises one or more paths (22) of flight external to said area and facing a same side of the selection frame (26) of the area itself.

5. The method according to any one of the preceding claims, comprising the step of establishing a second surveillance strategy that envisages subdividing said more stretches (22area into a pair of sub-areas (27', 27'') via a midplane and comprises a flight path provided with two flight paths (22',22''), set on opposite sides of the selection frame (26) of said area with respect to said midplane.

6. The method according to Claims 4 and 5, wherein the flight path provided in said first surveillance strategy or in said second surveillance strategy comprises at least one circular standby orbit of said aircraft (2) , which is centred along one said path and has a pre-set radius (R) .

7. The method according to any one of the preceding claims, comprising the step of establishing a third surveillance strategy, which envisages subdividing said selected area into a plurality of sub-areas (27 ' , 27 ' ' , 27 ' ' ' ) and comprises a flight path provided with a series of flight paths (22) , each set along the longitudinal axis (ALi) of a corresponding sub- area (27' ,27' ' ,27' ' ' ) .

8. The method according to any one of Claims 4 to 7 , wherein said first or second or third surveillance strategy comprises at least one scanning path that follows a path substantially shaped like a fret within said area or sub-area; said scanning path being provided with a series of first stretches (24) and second stretches (25) , which are respectively set parallel and transverse to a longitudinal axis (AL) (ALi) of said area or sub-area (27 ' , 27' ' , 27 ' ' ' ) .

9. The method according to the preceding claims, comprising the step of establishing, for each of said areas, a stand-off constraint indicating a minimum distance (Dso) that the aircraft (2) must keep with respect to said area, and the step of establishing a set of constraints correlated to the flight of said aircraft (2) .

10. The method according to Claim 9, wherein said selection frame (26) (26') (41) is designed to delimit alternatively a first type of area corresponding to a surface portion associated to an area of vast dimensions, or a second type of area corresponding to a surface portion associated to an area of limited proportions, or a third type of area corresponding to a strip, or a fourth type of area corresponding to a point element .

11. The method according to Claim 10, wherein if said selected area corresponds to said first type, and a stand-off constraint has been established, said step g) comprises the step of determining said maximum reconnoitring distance (DMR) applying the relation DMR = Kψ φ_so + 2R + H)² + hv²) where: K is a constant equal to approximately 1.3; H is the width of said area; hv is a pre-set reconnoitring height of said aircraft (2) ; and R is a pre-set radius of the standby orbits of said aircraft envisaged during said flight path.

12. The method according to Claims 10 and 11, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan the flight path envisaged in said first surveillance strategy.

13. The method according to Claims 10 and 11, wherein, if said selected area corresponds to said first type and a stand-off constraint has been established, said step g) comprises the step of determining said maximum reconnoitring distance (DMR) applying the relation DMR = Ky(OD₃₀ + ZR + H / 2)² + hv²), where K is a constant equal to approximately 1.3; H is the width of said area; hv is a pre-set reconnoitring height of said aircraft (2) ; and R is a pre-set radius of the standby orbits of said aircraft envisaged during said flight path.

14. The method according to Claim 13, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan the flight path envisaged in said second surveillance strategy.

15. The method according to Claim 12 or Claim 14, comprising the step of configuring the path of scanning of said area or sub-area (27' , 27' ' , 27' ' ' ) calculating the points Psj (Xsj , Ysj , Zsj ) that join said first scanning stretches (24) and second scanning stretches (25) by applying the following relations: XsJ=I* (1-Ot) /2+ (1+ (-l)πx) *ST/2; Ysj=h(l- Ot) /2+ny* (SL-I) ; where nx=Int (j /2) +1 and ny=Int ( (j +1) /2) , whilst j is an index ranging between 1 and 2*Nps.

16. The method according to Claim 11, wherein, if no stand-off constraint has been established and said selected area corresponds to said first type, said step g) comprises the step of determining said maximum reconnoitring distance (DMR) applying the relation DMR = K-J{ (As / 2)² + hv²) where As is a width of the observation band of the area.

17. The method according to Claim 16, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan the flight path envisaged in said second surveillance strategy.

18. The method according to Claim 17, comprising the step of configuring the scanning path of said area by defining the points Psi, j (Xsij , Ysij , Zsij ) that delimit said first (24) and second (25) scanning stretches within the area applying the relations :

Xsij=hi* (1-Ot) /2+(1+(-I)¹¹*) *ST/2+DL* (i-1) ;

Ysij=(li* (1-Ot) /2+ny* (SL-I) ) (l+(-l) ^<i+1) ) /2+ (L-Ii* (1-Ot) /2- ny* (SL-I) ) (1+ (-1) ^¹' ) /2; where j ranges between 1 and 2*Nps, and i ranges between 1 and Nl, whilst nx=Int (j/2) +1 and ny=lnt( (j+l)/2) .

19. The method according to Claim 11, wherein said step a) comprises the step of tracing a series of elongated rectangular segments (41) delimiting said strip associated to said third type of area.

20. The method according to Claim 19, wherein, if a stand-off constraint has been established and said selected area corresponds to said third type, said step g) comprises the step of determining said maximum reconnoitring distance (DMR) applying the relation DMR = K>/( (Dso + 2R + H)² + hv²) where K is a constant equal to approximately 1.3.

21. The method according to Claim 20, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan corresponding to each segment the flight path envisaged in said first planning strategy.

22. The method according to Claim 19, wherein, if a stand-off constraint has not been established and said selected area corresponds to said third type, said step g) comprises the step of establishing a stand-off constraint, of assigning a pre-set value to the stand-off distance (Dso) , and of determining said maximum reconnoitring distance (DMR) by applying the relation DMR = Kyji (Dso + 2R + H)² + hv²) , where K is a constant of value equal to approximately 1.3.

23. The method according to Claim 22, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan corresponding to each segment the flight path envisaged in said first planning strategy or said third planning strategy.

24. The method according to Claim 11, wherein if said selected area corresponds to said second type, said step g) comprises the step of determining said maximum reconnoitring distance (DMR) by applying the relation DMR = κV( (Dso + 2R + H)² + L² + hv²) ; or alternatively DMR = K-v/( (H / 2)² + (L + R)² + hv²).

25. The method according to Claim 24, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan the flight path envisaged in said first planning strategy.

26. The method according to Claim 11, wherein, if said selected area corresponds to said fourth type, said step g) comprises the step of determining said maximum reconnoitring distance (DMR) by applying the relation DMR = KV( (Dso + 2R)² + hv²) or in case of absence of the standoff constraint DMR = K-^(R² + hv²) ; where K =1.

27. The method according to Claim 26, wherein, if said second condition of observability is satisfied, the step is envisaged of assigning to the flight plan a flight path having a substantially circular orbit centred on the element to be observed or set at a pre-set distance from the element itself.

28. A device (11) for planning a mission of surveillance of one or more areas set on a territory via a reconnaissance aircraft (2), which is designed to acquire the images of said areas for transmitting them to a remote surveillance station

(5) , which processes said images for detecting the presence/absence of targets within the areas observed; said aircraft (2) comprising image-acquisition means (3) designed to carry out a scan of each of said areas to be observed, and control means (2a) (5a) , designed to pilot said aircraft (2) ; said remote surveillance station (5) comprising display means

(5c) , designed to display a digital cartographic map representing said • territory, control means (12), designed to enable an operator to select one or more areas to be observed on said digital map, and processing means (11) , designed to plan said surveillance mission, comprising a flight plan containing a flight path of said aircraft (2) and an observation plan containing a path of scanning of the images of the area by said acquisition means (3) ; said device (11) being installed in said surveillance station (5) and being characterized in that it comprises: means for detecting one or more selection frames (26) (26') (41) traced by the operator on said digital map via said control means (12) and containing each an area to be observed;

- means for establishing at least one first display constraint correlated to a state of minimum visibility of the target that can be set by the operator via said control means (12) and can be represented in the image during display of the image itself through said display means (5c) ; means for establishing at least one second display constraint correlated to the minimum dimension (DOmin) of the target that can be set by the operator via said control means (12) and can be represented within the image during display of the image itself through said display means (5c) ;

- means for determining a set of main parameters correlated to the capacity of observation of said areas by said acquisition means (3), and/or to the capacity of acquisition of the image of the areas themselves by said acquisition means (3) ; means for determining a set of secondary parameters correlated to the conditions of environmental visibility present in said areas,-

- means designed to calculate, for each of said areas selected on said map, a maximum threshold of observability (DMOC) of said target by said acquisition means (3) as a function of said main and/or secondary parameters; said maximum threshold of observability (DMOC) corresponding to the maximum distance of positioning of said acquisition means (3) with respect to said area, beyond- which the representation of said target in said image does not satisfy said first and/or second constraint;

- means designed to calculate, for each of said areas selected on said map, a maximum reconnoitring distance (DMR) of the aircraft (2) from said area according to the area itself; and - means designed to signal, for each of said areas selected on said map a condition of impossibility of planning said surveillance mission when said maximum reconnoitring distance (DMR) and said maximum threshold of observability (DMOC) satisfy between them a first pre-set condition of observability.

29. A computer, characterized in that it implements a method as indicated in any one of Claims 1 to 27.

30. A software product that can be loaded into the memory of processing means (11) and is designed for implementing, when run, the method according to any one of Claims 1 to 27.