Method and system for generating a probability map for a carrier detected by a detection system

Description

[0001] The invention relates to the field of analysis of enemy detection systems, such as electromagnetic wave transmitters / receivers, for example communication devices or radar devices.

[0002] The invention relates more specifically to a method for determining, for an allied carrier, the probability of being detected by an enemy detection system in a given area. The carrier is, for example, an aircraft. Thus, the invention provides decision-making assistance for the aircraft pilot to determine the movement areas in which it is not likely to be detected.

[0003] In the case where the enemy detection systems have a fixed position, it is possible to locate them, for example using satellite or other means, once and for all before the aircraft leaves.

[0004] When these systems are mobile, this is more difficult because their positions can change between the time of location and the aircraft's mission.

[0005] Furthermore, the transmitters to be located can be mounted on vehicles of various types, including those which may have varying sizes. For example, large vehicles are generally not very mobile, while medium-sized vehicles may be more mobile.

[0006] During a surveillance mission, the position of the medium-scale detection systems to be located is not known with certainty, which contributes to increasing the risk level of the mission or to prohibiting overflight of large areas considered to be at high risk because there is a high probability of the presence of this type of detection system.

[0007] Risk zones are generally defined in relation to the ranges of detection systems.

[0008] The general technical problem addressed by the invention consists, for an allied carrier, in estimating geographical areas in which the probability is high that it will be detected by enemy equipment having detection capabilities.

[0009] Prior art solutions are most often based on defining a priori detection risk zones, based on the assumed positions of the detection systems. The positions can be estimated from location sensors or by a priori information. The detection probability is generally defined in a binary way, having a value of 0 except in a disk centered on the assumed position of the detection system.

[0010] Document US2011 / 0029234A1 "threat analysis toolkit" discloses a system for modifying the navigation points of an aircraft's route based on identified threats from ground radar with a fixed position or from airborne radar with a mobile but known position.

[0011] However, these solutions do not take into account the inaccuracies in the location of detection systems, which can lead to the definition of erroneous risk zones. They also do not take into account the phenomena of signal masking by the terrain.

[0012] The invention proposes a method for generating a probability map of risk zones, i.e. zones in which a carrier can be detected by a detection system with a certain probability.

[0013] The invention makes it possible to improve the realism of these areas by taking into account the location inaccuracies of the detection systems but also the impact of the relief on their detection capacity.

[0014] The subject of the invention is a computer-implemented method for generating a probability map, for a carrier, of being detected by at least one detection system having a predefined maximum detection range ρ, the method comprising the steps of: Determine a probability of presence of at least one detection system as a function of its position. For each point M in a given geographical area, integrate the probability of presence on a disk with center M and radius equal to the maximum range ρ. Generate, at each point M, a probability of being detected by at least one detection system equal to the result of the previous integration.

[0015] In an alternative embodiment, the invention further comprises the steps of, for each detection system: Calculate information representative of the intervisibility between the wearer and the detection system, taking into account the terrain relief, Weight the probability of presence of the detection system by the information representative of the intervisibility.

[0016] According to a particular aspect of the invention, the information representative of intervisibility is equal to 1 if the wearer and the detection system are intervisible in view of the relief and is equal to 0 otherwise.

[0017] According to a particular aspect of the invention, the information representative of intervisibility is determined from a digital model of the terrain by checking whether or not the straight line connecting the wearer and the detection system has an intersection with the digital model of the terrain.

[0018] In an alternative embodiment, the invention further comprises a step of generating, at each point M, a probability of being detected by several detection systems, equal to the union of the probabilities of being detected by each detection system.

[0019] According to a particular aspect of the invention, the probability of presence of at least one detection system is determined by means of a location sensor.

[0020] According to a particular aspect of the invention, the location sensor is a radar, a passive triangulation location sensor or an optronic sensor.

[0021] In an alternative embodiment, the invention further comprises a step of displaying the map on a visualization interface.

[0022] The invention also relates to a system for generating a probability map, for a carrier, of being detected by at least one detection system having a predefined maximum detection range ρ, the system being configured to execute the steps of the method according to the invention.

[0023] Other features and advantages of the present invention will become more apparent upon reading the following description in relation to the following appended drawings. [ Fig. 1 ] there figure 1 represents a flowchart detailing the steps of implementing the method according to the invention, [ Fig. 2 ] there figure 2 represents, on a diagram, the principle of calculating the probability of risk of detection according to the invention, [ Fig. 3 ] there figure 3 represents an illustration of the consideration of the masking of a signal by the relief, [ Fig. 4 ] there figure 4represents two examples of probability maps of the presence of a detection system, [ Fig. 5 ] there figure 5 represents an example of a digital terrain model, [ Fig. 6 ] there figure 6 represents an example of maps of risk zones of being detected by a detection system, [ Fig. 7 ] there figure 7 represents an example of a map of risk zones of being detected by detection systems, [ Fig. 8 ] there figure 8 represents a diagram of a system for generating a risk zone map according to the invention.

[0024] The invention aims to determine a map of detection risk zones, at each point, by a detection system. The term detection system designates equipment comprising at least one electromagnetic wave transmitter / receiver having the capacity to detect waves emitted by another transmitter. This is, for example, a radar system.

[0025] The main steps of implementing the method according to the invention are shown diagrammatically in figure 1 .

[0026] The first step is to determine the probability of the presence of a detection system. We first consider the situation of potential detection by a system consisting of a single piece of detection equipment. The detection system is equipment comprising means for transmitting / receiving electromagnetic waves and / or the ability to detect the emission of electromagnetic waves by another transmitter.

[0027] Thus, the targeted situation corresponds to an allied platform located at a point M for which we seek to evaluate the probability of being detected by a detection system located at a point E. This example is shown diagrammatically in figure 2 .

[0028] For a point M on the map, with coordinates (x,y), we wish to determine the probability of detection by the system E with coordinates (x E ,y E ). We consider that the detection range of the system E is known and equal to ρ and that its probability of presence at a point (x,y) of the map is given by f E ( x, y ) .

[0029] The probability f E ( x, y ) can be determined beforehand by detection equipment comprising a location sensor, for example a SAR imaging radar, a passive triangulation location sensor, or an optronic sensor, for example a visible optical or infrared optical imaging sensor.

[0030] If the sensor provides a location in the form of an uncertainty ellipse, there is a literal expression defining f E . Generally, uncertainty ellipses are defined by their center (estimated position) µ E and their covariance matrix Σ E . The density f E is then given by the binormal distribution: f E X = 1 2 π Σ E 1 / 2 exp − 1 2 X − μ E T Σ E − 1 X − μ E

[0031] With X = [x,y] T< .

[0032] Without departing from the scope of the invention, the location probability f E can be obtained by merging various sources of information including in particular location information taking into account the semantics of the terrain, the relief or a priori information on the systems to be located.

[0033] In a second step 102, a probability is then determined that an allied platform located at point M is detected by a detection system located at point E.

[0034] This probability is given by the following relation: P D ≤ ρ = ∫ 0 ρ f D r dr

[0035] D is the distance between M and E and f D ( r ) is the probability density of the presence of system E as a function of distance D.

[0036] In the end, we show that: <menclose notation="box"> P D ≤ ρ = ∬ C M f E x y dx dy < / menclose>

[0037] Or is the center disk M and radius ρ.

[0038] A risk zone map is obtained by calculating the above probability for a set of points on the plane, for example on a grid with a given pitch for a predetermined geographical area.

[0039] In an optional step 203, we take into account the cases where masking linked to the relief can reduce the range of the adversary detection system E in certain zones. For this, we are interested in the intervisibility between the detection system E and the allied platform M. There is intervisibility when we can draw a straight line segment between the two points E and M without intercepting the terrain.

[0040] We assume that we have a digital terrain model that allows us to create a function giving the altitude of the terrain at a point with coordinates (x,y). We note this function z MNT ( x, y ) .

[0041] The intervisibility condition between the coordinate detection system E ( x E , y E , z E ) and a platform located at a point M with coordinates ( x M, y M , z M ) can be expressed as the following condition: points E and M are intervisible if the following relation is respected.

[0042] z MNT ( x E + k ( x M - x E ) , and E + k ( and M - and E )) < z E +k ( z M -z E ), for all real values of k between 0 and 1.

[0043] There figure 3 represents an example of a digital terrain model and illustrates a situation where points E and M are not intervisible because the line connecting them intercepts the relief.

[0044] We determine an indicator function of the intervisibility between points E and M.

[0045] We note 1 M ( x E , and E ) this function.

[0046] For example, this function is 1 if points E and M are intervisible and 0 otherwise.

[0047] The detection probability taking into account intervisibility can then be calculated as follows: <menclose notation="box"> P D ≤ ρ = ∬ C M 1 M x y f E x y dx dy < / menclose>

[0048] This expression depends on the platform coordinates M . By calculating P ( D ≤ ρ ) by varying ( x M ,and M ) with z M constant, we obtain a map of the risk of detection at altitude z M It is possible to calculate different detection probability maps at different altitudes if necessary.

[0049] If the overall detection system is composed of N networked detection subsystems E 1 ,... IN ,each having detection capabilities within a respective detection radius (range) ρ 1 , ..., ρ N , then the probability of being detected by at least one of these subsystems is equal to the union of the probabilities of being detected by each subsystem. It is given by the following relation: <menclose notation="box"> P D 1 ≤ ρ 1 ∪ D 2 ≤ ρ 2 ∪ … ∪ D N ≤ ρ N = 1 − ∏ n = 1 N 1 − P D n < ρ n < / menclose>

[0050] THE figures , 5 , 6 And 7 illustrate an example of application of the invention. In this example, we consider an area of interest where two detection systems E 1 and E 2 in range ρ 1 and ρ 2 are present. A geolocation system has previously made it possible to determine a rough estimate of the position of these detection systems. This information on the position is defined by the probability density maps of presence f E 1 and f E 2 represented at the figure 4 . Detection systemsE 1 and E 2 are located respectively inside the zone And .

[0051] We also have a digital terrain model z MNT ( x, y ) on the area of interest. This model is represented in the figure 5 .

[0052] From the densities f E 1 and f E 2, litters ρ 1 , ρ 2 as well as the digital terrain model z MNT , using the method according to the invention, it is possible to calculate P ( D 1 ≤ ρ 1) and P ( D 2 ≤ ρ 2 ) the individual detection probabilities for the detection systems E 1 and E 2 .

[0053] These probabilities are represented in the form of detection risk maps at the figure 6 .

[0054] The overall risk map associated with the system composed of the two detection systems is then obtained by calculating the union of the probabilities for each of the detection systems as explained above. The final result is shown in figure 7 .

[0055] The map shown in the figure 7 allows you to highlight areas where the risk of being detected by the overall system is very low (in black). For example, on the figure 7 , the ZR zone identified at the figure 7 is a relief masking zone that allows a platform to remain undetected.

[0056] There figure 8 represents a functional diagram of an exemplary system 800 configured to implement the invention.

[0057] The system 800 comprises a module 801 for calculating the probability of presence of a detection system which receives as input data from one or more location sensors LOC and data from a knowledge base B, in particular providing information on the range of the detection systems. An intervisibility calculation module 802 interacts with the probability calculation module 801 by exploiting a digital terrain model DTM. The module 801 performs a probability calculation for each detection subsystem of a global detection system, then provides the results to a fusion module 803 which calculates the final probability in the form of a risk zone map CZR.

[0058] Each of the elements of the system 800 according to the invention can be implemented in software and / or hardware form from a processor and a memory. The processor can be a generic processor, a specific processor, an application-specific integrated circuit (also known as ASIC for “Application-Specific Integrated Circuit”) or an in situ programmable gate array (also known as FPGA for “Field-Programmable Gate Array”).

[0059] The invention may also be implemented as a computer program comprising instructions for its execution. The computer program may be recorded on a recording medium readable by a processor. Reference to a computer program that, when executed, performs any of the functions described above, is not limited to an application program running on a single host computer. Rather, the terms computer program and software are used herein in a general sense to refer to any type of computer code (e.g., application software, firmware, microcode, or any other form of computer instruction) that can be used to program one or more processors to implement aspects of the techniques described herein. In particular, the computing means or resources may be distributed (" Cloud computing" ) ,possibly using peer-to-peer technologies. The software code may be executed on any suitable processor (e.g., a microprocessor) or processor core or a set of processors, whether provided in a single computing device or distributed among several computing devices (e.g., as may be accessible in the device environment). The executable code of each program enabling the programmable device to implement the processes according to the invention may be stored, for example, in the hard disk or in read-only memory. Generally, the program(s) may be loaded into one of the storage means of the device before being executed.The central unit can control and direct the execution of the instructions or portions of software code of the program(s) according to the invention, instructions which are stored in the hard disk or in the read-only memory or in the other aforementioned storage elements. The executable code can also be downloaded from a remote server.

[0060] The computer program may comprise source code, object code, intermediate source code or partially compiled object code or any other form of program code instructions suitable for implementing the invention in the form of a computer program.

[0061] Such a program may have various functional architectures. For example, a computer program according to the invention may be decomposed into one or more routines that may be adapted to execute one or more functions of the invention as described above. The routines may be recorded together in a single executable file but may also be saved in one or more external files in the form of libraries that are associated with a main program statically or dynamically. The routines may be called from the main program but may also include calls to other routines or subroutines.

[0062] All methods or method steps, programs or subroutines described in flowchart form are to be interpreted as corresponding to modules, segments or portions of program code which include one or more code instructions for implementing the logical functions and steps of the invention described.

[0063] The final CZR probability map can be rendered to a user via a graphical interface, for example a display screen or other equivalent means.

[0064] The system 800 may be carried on board a mobile carrier, for example an aircraft.

Claims

1. A computer-implemented method for generating a map of the probability of a carrier being detected by at least one detection system with a predefined maximum detection range ρ, the method comprising the steps of: - determining (101) a probability of the presence of at least one detection system as a function of its position; - integrating, for each point M of a given geographical area corresponding to a position of the carrier, the probability of the presence on a disk with a centre M and with a radius that is equal to the maximum range ρ; - generating (102), at each point M, a probability of being detected by at least one detection system that is equal to the result of the previous integration.

2. The method for generating a map of the probability of being detected according to claim 1, further comprising, for each detection system, the steps of: - computing (103) information representing the intervisibility between the carrier and the detection system, taking into account the relief of the terrain; - weighting the probability of the presence of the detection system through the information representing the intervisibility.

3. The method for generating a map of the probability of being detected according to claim 2, wherein the information representing the intervisibility is equal to 1 if the carrier and the detection system are intervisible in view of the relief, and is otherwise equal to 0.

4. The method for generating a map of the probability of being detected according to any one of claims 2 or 3, wherein the information representing the intervisibility is determined based on a digital model of the terrain by checking whether the straight line connecting the carrier and the detection system has or does not have an intersection with the digital model of the terrain.

5. The method for generating a map of the probability of being detected according to any of the preceding claims, further comprising a step of generating, at each point M, a probability of being detected by several detection systems, equal to the combination of the probabilities of being detected by each detection system.

6. The method for generating a map of the probability of being detected according to any of the preceding claims, wherein the probability of the presence of at least one detection system is determined by means of a location sensor.

7. The method for generating a map of the probability of being detected according to claim 6, wherein the location sensor is a radar, a passive triangulation location sensor or an optronic sensor.

8. The method for generating a map of the probability of being detected according to any of the preceding claims, further comprising a step of displaying the map on a visualisation interface.

9. A system (800) for generating a map of the probability of a carrier being detected by at least one detection system with a predefined maximum detection range ρ, the system being configured to execute the steps of the method according to any one of the preceding claims.