Air traffic monitoring process

Abstract

This document relates to a method for detecting an aircraft in the landing phase on an aerodrome, in particular an uncontrolled aerodrome, the aerodrome comprising at least one runway (V1) having at least two ends (E1, E2), and by means of an optronic system comprising at least one primary camera of which a primary angular aperture is oriented towards a first end (E1) of the runway, the method comprising determining the presence or not, in an approach region, of an object compatible with an aircraft, and where appropriate analyzing the path of the detected object by comparing its current position with a history of the positions of objects detected in an analysis zone. Abstract figure: Figure 14

Description

Title of the invention: Method for monitoring air traffic Technical field

[0001] The present disclosure relates to the field of air traffic monitoring systems and methods, more particularly for uncontrolled aerodromes. Prior art

[0002] Controlled and uncontrolled aerodromes are two types of airport infrastructure that differ in the presence or absence of a control tower and air traffic control services. Each of these types offers distinct characteristics and procedures for pilots and aircraft operations.

[0003] A controlled aerodrome has a control tower where air traffic controllers work to manage aircraft movements. ATCs (Air Traffic Controllers) ensure the safety of flight operations by providing air traffic control services, such as managing takeoffs, landings, and in-flight traffic. Pilots establish radio communication with the control tower and follow instructions issued by controllers for their movements on the aerodrome and in the surrounding controlled airspace. Controlled aerodromes also offer advanced navigation instruments, such as approach aids and instrument landing systems (ILS), which facilitate flight operations in adverse weather conditions.

[0004] In contrast, uncontrolled airfields do not have a control tower or air traffic controllers. Pilots operating at these airfields use a specific radio frequency to communicate with each other and share information about movements at the airfield. They are responsible for their own safety and air traffic management, following standard procedures and exercising increased vigilance to avoid potential conflicts with other aircraft. Uncontrolled airfields are usually equipped with visual aids such as beacons, runway identification signs, and ground markings to aid pilot navigation.

[0005] Uncontrolled aerodromes far outnumber controlled aerodromes, as many rural and remote areas do not require air traffic control services.

[0006] In many countries there are a large number of uncontrolled aerodromes used primarily for general aviation, recreational flying, agricultural operations, training flights, etc. These aerodromes may be small local facilities, training airfields, air sports airfields, relief airfields, and many more. For example, in France, there are approximately 450 to 500 uncontrolled airfields.

[0007] Uncontrolled aerodromes can be classified into two categories depending on whether they include an AFIS (Aerodrome Flight Information Service) service or not.

[0008] AFIS (Aerodrome Flight Information Service) is a type of air traffic control service provided at some uncontrolled aerodromes. Unlike controlled aerodromes that have a control tower and air traffic controllers, uncontrolled aerodromes with AFIS have a Flight Information Service.

[0009] The AFIS service is usually provided by qualified personnel called "Flight Information Service Officer" (FISO). FISOs are responsible for providing information and advice to pilots operating at and around the aerodrome. Their main role is to ensure the safety of flight operations by providing relevant information on weather conditions, local air traffic, aerodrome procedures and other useful information to pilots.

[0010] FISOs are responsible for monitoring air traffic using visual means, such as binoculars or electronic devices, to assist in the identification and separation of aircraft. They may also provide guidance and instructions to pilots, including ground movements, takeoffs and landings, while coordinating aircraft activities on the airfield.

[0011] It is important to note that the AFIS service does not constitute air traffic control in the strict sense, but it provides pilots with a source of information and support to help them make informed decisions regarding their flights. It aims to improve the safety of operations at uncontrolled aerodromes by providing limited but valuable assistance to pilots.

[0012] More and more controlled airfields are being transformed into uncontrolled airfields due to insufficient air traffic and / or increasing operating costs (standards to be respected, etc.).

[0013] However, passing through an uncontrolled aerodrome leads to the following difficulties: - knowing the air traffic of an aerodrome, - collecting the fees associated with this air traffic, - knowing the state of the infrastructure (state of the runways, fire, accident, etc.) - arranging flight schedules to optimize the noise around the aerodrome.

[0014] It is therefore understood that the detection of aircraft on an uncontrolled aerodrome is important. To this end, automatic air traffic detection systems have already been proposed. They are based on: - optical or radar systems from the automotive industry, with ranges of a few dozen meters, which requires the installation of equipment at each exit from an aerodrome taxiway, - cooperative surveillance systems of the ADS-B type (Automatic dependent surveillance-broadcast), but which only equip a very limited part of the aerodrome aircraft fleet (around 10 to 20%), - TCAS (Traffic Alert and Collision Avoidance System) systems, but which equip a very limited part of the aerodrome aircraft fleet, since this concerns aircraft weighing more than 5,700 kg or those authorized to carry more than 19 passengers which do not constitute the majority of the aircraft fleet using uncontrolled aerodromes.

[0015] These systems prove restrictive in terms of installation for the aerodrome manager, and do not cover all of the aerodrome's air traffic.

[0016] Furthermore, none of the current systems allows simple and rapid tracking of an aircraft in such a way as to provide certain information on the landing of an aircraft.

[0017] Currently, the great variability of situations on aerodromes prevents the development of an algorithm that is sufficiently reliable to detect an aircraft and only an aircraft. Among the elements that impact detection, we will note: - The movement of trees in strong winds, - The movement of grass in average wind, - Cloud shadows on the ground moving, - Clouds of smoke, - Cars driving in the camera field, - Birds, which depending on their location, have the apparent size of an airplane for the camera.

[0018] This document therefore aims to propose a universal air traffic monitoring solution that is simple to implement. Summary

[0019] The present document relates to a method for detecting an aircraft in the landing phase on an aerodrome, in particular an uncontrolled one, the aerodrome comprising at least one runway having at least two ends, and by means of an optronic system comprising at least one primary camera of which a primary angular aperture is oriented towards a first end of the runway, the method comprising the steps: - Determination of a set of possible approach trajectories on said at least one runway, - Determining a position of said at least one primary camera so that its primary angular aperture includes said set of possible trajectories, - Determination, in the primary angular aperture, of an analysis zone shaped so as to include all of said approach trajectories and preferably located above the horizon; - Determination of an end-of-approach region in the analysis zone; - Carrying out, in the said analysis zone, a detection of objects having a size compatible with that of an aircraft, - Determination of the presence or absence, in the approach region, of an object compatible with an aircraft, and if necessary analysis of the path of the detected object by comparison of its current position with a history of the positions of objects detected in the analysis zone and included in the database.

[0020] In practice, over at least one day or several, aircraft flights are recorded so as to identify all possible trajectories. It is advisable to have at least a hundred flights to be certain of having all possible trajectories. It is understood that the set of approach trajectories is a set making it possible to position the approach trajectories in three dimensions relative to the runway.

[0021] The aircraft approach zone can thus be chosen to be less than the primary angular aperture of the second camera, which makes it possible to reduce the zone analyzed in real time.

[0022] According to another characteristic, the indication that an aircraft is in the approach phase can be carried out by verifying that: a. At least one object has been detected in the approach zone and on at least k Im-S4 images;, i varying from 1 to k, temporally preceding the Im-S4a image for which an object was detected in the end-of-approach region, b. there are at least k hn-S4i images comprising at least one object of a size compatible with that of an aircraft and the abscissa of each of the objects is greater (or less depending on whether the object assumed to be an aircraft is arriving towards one end or the other of the runway) than the abscissa of the object detected in the end-of-approach region, c. determine all possible paths between the objects of the successive Im-S4 images; i varying from 1 to k, and leading to the object identified on the hn-S4a image, then we validate whether a trajectory follows a straight line or not.

[0023] According to the present document, the three aforementioned conditions must have been validated in order to be able to confirm that an aircraft is indeed in the approach region. The last linear regression step makes it possible to confirm the non-chaotic aspect of the trajectory. Indeed, a chaotic trajectory would be incompatible with the trajectory of an aircraft but could be compatible with the trajectory of a bird having a size compatible with that of an aircraft, due for example to a location closer than that of an aircraft.

[0024] The optronic system may comprise at least one second primary camera of which a primary angular aperture is oriented towards a second end of the track, the method comprising: - identification of possible runway exit trajectories for an aircraft at the second end of the runway; - the classification of said possible trajectories into three possible behaviors, a first behavior corresponding to an actual landing, a second behavior corresponding to a runway touchdown without landing and the third behavior corresponding to an overflight of the runway at low altitude, - Determination of a position of the second primary camera so that its primary angular aperture includes all possible runway exit trajectories, - Determination, in the primary angular aperture of the second camera, of three zones, a first end-of-runway zone corresponding to the first behavior, a second end-of-runway zone corresponding to the second behavior and a third end-of-runway zone corresponding to the third behavior.

[0025] From an aircraft approach trajectory, it is difficult to determine whether the aircraft will actually land, just touch the runway or just fly over the runway at low altitude. Since discrimination between these three scenarios is not possible from the approach trajectory alone, an analysis must then be carried out using a second primary camera arranged at the second end of the runway.

[0026] Obviously, it is understood that the first primary camera can play the role of the second primary camera depending on the direction of aircraft landings.

[0027] A runway exit trajectory is here an exit trajectory from the second end observation zone of the runway.

[0028] The method may further comprise: - Continuous recording of the primary camera's angular aperture, - For a given image at a given time t: • take the average of x images temporally preceding the given image and obtain an averaged image, • Subtract the given image from the averaged image.

[0029] The average of the previous x images is performed pixel by pixel. The number x of images used to perform the average is important and will be determined by successive iterations.

[0030] Preferably, a dilation step will be applied to the given image.

[0031] This expansion step makes it possible to close the contours. Preferably, objects having a surface area greater than a predetermined size are eliminated.

[0032] The position of the primary camera may be determined such that its primary angular aperture includes an intersection of said at least one runway with a taxiway.

[0033] A taxiway is an access route for the aircraft to the takeoff / landing runway from an aircraft stopping area. According to the present document, the primary angular aperture of a primary camera comprises both an end of the runway and said junction area, which makes it possible to identify that an aircraft is entering or leaving the runway.

[0034] The method may include determining an intersection region within the primary angular aperture of the primary camera, wherein the intersection region encompasses the intersection of the runway with the taxiway.

[0035] The analysis zone may comprise an approach zone delimited below by a first low line arranged above the runway and above by a second high line arranged above the first line, the approach zone being connected to the approach end region.

[0036] The first low line may have an inclination of a non-zero angle α relative to the axis of said at least one track, α may be greater than or equal to 3°.

[0037] The minimum angle should be chosen as the minimum value given by an administration competent in aeronautical legislation for the aerodrome considered. In France, the minimum value is 3° with a possible deviation of 0.5°.

[0038] This inclination greater than at least 3° relative to the axis of the runway makes it possible to remove part of the decoration likely to lead to so-called false positive detections of an aircraft.

[0039] The second upper line may have an inclination of an angle [3 greater than the angle a, the angle [3 being determined as corresponding to the maximum possible angle of arrival of an aircraft on said at least one runway.

[0040] In practice, a value of 9° corresponds to an approach standard.

[0041] The optronic system used with the method described above may comprise a secondary camera mobile in rotation around a vertical axis so that its optical axis can follow a moving aircraft, the method comprising a subsequent step of tracking an aircraft after indicating the presence of an aircraft in the approach region. Brief description of the drawings

[0042] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0043] [Fig-1] illustrates an optronic system according to the present document in an undeployed position in Figure 1A and in a deployed and ready-to-use position in Figure 1B;

[0044] [Fig.2] is a schematic perspective view of an optronic system according to the present document in an undeployed position, the system being shown without the support elements visible in [Fig.l];

[0045] [Fig.3] is a schematic perspective view of a portion of the mast supporting a plurality of primary cameras and in a bottom-up orientation.

[0046] [Fig.4] is an enlarged view of the means for moving each primary camera in order to achieve static positioning of the primary camera in a desired position.

[0047] [Fig.5] is a schematic view of the system, similar to [Fig.3], and viewed in a top-down orientation;

[0048] [Fig.6] represents a flowchart of interaction of the means of controlling the movement of the secondary camera;

[0049] [Fig.7] is a schematic view illustrating several existing takeoff / landing runway configurations at an uncontrolled airfield;

[0050] [Fig.9] comprises a part A which represents an image of an area of ​​space observed through an angular aperture of a first primary camera oriented towards a first end of a runway and part B represents an image of an area of ​​space observed through an angular aperture of a second primary camera oriented towards a second end of the runway;

[0051] [Fig. 10] is an image of another area of ​​space observed through an angular aperture of a primary camera oriented towards another end of a track;

[0052] [Fig. 11] is an enlarged image of a portion of [Fig. 10];

[0053] [Fig. 12] is an illustration of the steps of detecting movement in the opening angular of a primary camera;

[0054] [Fig. 13] is an illustration of several attempts to detect motion in a given image acquired by the primary camera;

[0055] [Fig. 14] is a flowchart of the steps of detecting objects and indicating the presence of an aircraft in an approach region;

[0056] [Fig. 15] illustrates different possible paths obtained from images stored in a database. Description of the embodiments

[0057] Reference is now made to [Fig. 1] which represents a system 10 according to the present document. The system 10 can be installed on a flat support 12 such as a concrete slab. It comprises a mast 14 carrying a secondary camera 16 movable in rotation around the longitudinal axis and at least two primary cameras 18 (better visible in [Fig.2]) which are fixed. By rotating mobile camera and fixed camera, it is meant that in operation the camera is able to move and by static or fixed camera, it is meant that the camera is fixed in operation, that is to say when the system is used. Obviously, for adjusting the positioning of the primary cameras 18, these can be connected to appropriate movement means as will be seen in the following.

[0058] The mast 14 may advantageously be telescopic as illustrated in FIGS. 1A and 1B and may thus comprise a plurality of tubular segments 15 arranged one inside the other. The system 10 is here surrounded by a protective enclosure 20 intended to prevent damage by unauthorized persons (intrusions) or due to impacts by aircraft (wingtip impacts). The mast 14 extends along a longitudinal axis L which is arranged in a vertical position. It comprises a lower end or first end 14a and an upper end or second end 14b. The mast 14 is held in a vertical position by a plurality of support arms 15 articulated in rotation between a support position and a waiting position.

[0059] Each camera 16, 18 comprises its own angular aperture. The secondary camera 16 comprises a secondary angular aperture 17. The system 10 comprises at least two primary cameras 18a, 18b. Thus, each primary camera is referenced 18 followed by a reference a, b, c, d... designating respectively the rank 1 for first, 2 for second, ... of the primary camera. The first primary camera is therefore noted 18a, the second primary camera is noted 18b, the third primary camera is noted 18c, etc.. .Each angular aperture is noted 18x where x is a letter designating the primary camera 18x. Each primary camera 18x comprises a primary angular aperture Px where x is a letter designating the angular aperture of the camera 18x.Thus, the first primary camera 18a has a primary aperture Pa, the second primary camera 18b has a primary aperture Pb, the third primary camera 18c has a primary aperture Pc, the fourth primary camera 18d has a primary aperture Pd,... As can be seen in [Fig.7], . the primary angular aperture Pa, Pb, Pc, Pd of each of the primary cameras 18a, 18b, 18c, 18d is greater than the secondary angular aperture 17.

[0060] The optronic system is suitable for installation on any type of uncontrolled aerodrome. It is thus suitable for installation on uncontrolled aerodromes having a runway configuration VI, V2 as shown in FIGS. 7A, 7B, 7C, 7D. It will be readily understood, in light of the description, that the invention is applicable to any type of aerodrome comprising one or more runways. The 2D configuration of the runways, i.e. the number of runways as well as the two-dimensional arrangement of the runway axes relative to each other, determines the number of primary cameras 18 required and the positioning of the primary cameras 18. In practice, when the aerodrome comprises more than two runways, it will be preferable to use more than one optronic system.In such a situation, an optronic system will advantageously comprise four primary cameras which are used to monitor the ends of two runways and another optronic device will be used to monitor the ends of the runways beyond said two runways.

[0061] In the configuration illustrated in the figures, the primary cameras 18 are positioned around the longitudinal axis L and are preferably arranged on a circle having a center located on the longitudinal axis L of the mast 14. In other words, the circle intercepts each primary camera 18. However, this does not mean that each primary camera 18 is positioned in space in the same way relative to this circle.

[0062] The secondary camera 16 is carried by the second end 14b of the mast 14. In one embodiment, the optical axis of the camera is intercepted by the longitudinal axis of the mast 14. It is observed that a protective wall 20 can be interposed between the primary cameras 18 and the secondary camera 16 (Figures 2 and 3). In [Fig.5], the protective wall 20 has been removed to facilitate viewing of the parts located beneath it. The protective wall 20 may have a frustoconical shape, the section of the wall 20 preferably having a section reducing towards the secondary camera 16.

[0063] Each primary camera 18 may be mounted on support means comprising means for moving the optical axis of the primary camera along at least one of the azimuthal orientation, the elevation orientation and a translation relative to a radial direction with respect to the longitudinal axis L.

[0064] The moving means may be motors illustrated at 22 and which may be arranged inside the mast 14 so as to protect them.

[0065] The means for moving each primary camera 18 are carried by a support 24 comprising a plate having a substantially triangular shape. One end of the plate 24 is integral with a ring 26 carried by the mast and another end carries the means for moving the optical axis of a primary camera 18 ([Fig.5]). The means for moving a primary camera 18 comprise means for moving in elevation, means for moving in azimuthal direction and means for moving in translation relative to the longitudinal axis L ([Fig.4]).

[0066] The elevation movement means comprise a yoke 28 secured to the primary camera 18 and an arm 30 articulated in rotation on the yoke 28. The articulation is produced along a horizontal axis 32, that is to say an axis perpendicular to the longitudinal axis and positioned so as to allow adjustment of the orientation of the axis of the primary camera 18 relative to a horizontal plane.

[0067] The azimuthal displacement means comprise the arm 30 which is mounted in rotation on a member 32 around a vertical axis 34 parallel to the longitudinal axis L.

[0068] The translational movement means comprise the member 32 and a rail 38, the member 32 being able to move along an axis 36. The rail may be a rail of the Picattiny® rail type.

[0069] The movement means are connected to motors arranged inside the mast 14.

[0070] As can be seen in [Fig. 5], the ring 26 comprises connectors, preferably a plurality of triplets connectors C1, C2, C3, each triplet being associated with a primary camera 18. Two connectors C1, C2 are provided for the transfer of video signals and a connector C3 is provided for the electrical power supply of a primary camera 18. These connectors make it possible to connect the video and electrical cables of a primary camera 18 to a static support of the mast 14.

[0071] According to the present disclosure, the system 10 may comprise means 40 for moving, in particular in rotation, the secondary camera 16 around the longitudinal axis L so as to move an optical axis of the secondary camera 16 over a predetermined angular distance D to perform dynamic tracking of an aircraft in the landing or takeoff phase, and means 42 for piloting the means 40 for moving. The piloting means 42 are connected to means 43 for recognizing and tracking an aircraft in a primary opening Px.Thus, the piloting means 42 in communication / link with the recognition and tracking means 43 are informed about the positioning of an aircraft in a static primary angular opening Px and make it possible to actuate the movement means 42 to carry out movement tracking of the aircraft in the secondary angular opening 17 - moving in rotation with the secondary camera 16 - to allow identification of the aircraft. The movement means 40 of the secondary camera 16 may also comprise means for moving the optical axis of the secondary camera 16 in elevation.

[0072] The piloting means 42 therefore receive positive detection information from an aircraft. This detection is carried out continuously from the images acquired in real time by each of the primary cameras 18. The analysis of the images from the cameras primary 18 is carried out in time and the detection can therefore be carried out in real time. [Fig.6] illustrates a flowchart of interaction between the secondary camera 16 connected to the movement means 40 which are controlled by the piloting means 42 which receive positive detection information of an aircraft detected in a primary opening Px of a primary camera 18. Each second camera is connected to recognition and tracking means 43 of an aircraft in the primary angular opening of a primary camera.

[0073] The means for identifying an aircraft are means for identifying the aircraft, i.e. means for recognizing the characters of a registration plate located on the aircraft. The recognition and tracking means 43 designate means for identifying the presence of an aircraft in the visual field of a primary camera 16 and for tracking it in the angular field Px.

[0074] The secondary camera 16 may be a SONY®- 4K 200-600mm, 12° - 4° SCMOS camera having a continuous x3 optical zoom extending between 200 to 600 mm. It may have a low light level 3 capability (ISO > 400,000). Each primary camera 18 may be a SONY- 4K FCB-ER8550, 4.4-88 mm, 60° - 3.5° CMOS camera and having a continuous x20 optical zoom between 4.4 and 88 mm.

[0075] We now refer to [Fig. 7] which represents different track configurations. In Figure 7A, the configuration is such that two tracks VI, V2 are parallel to each other. In Figure 7B, the configuration is such that two tracks VI, V2 form a non-zero angle with respect to each other and do not intercept each other, the tracks VI, V2 forming an angle less than 90° and in this case approximately 40°. In Figure 7C, the configuration is such that two tracks VI, V2 intercept each other with an angle less than 90°, in this case of the order of 30°. In Figure 7D, the tracks VI, V2 are perpendicular to each other and intercept each other and in this case substantially in their middle.

[0076] In the different configurations illustrated, the primary angular apertures Px of the primary cameras 18 are all identical. They could still be different. Each runway VI, V2 comprises a first end El and a second end E2. An aircraft can take off and land from one end El or E2 of each runway, depending on the wind direction.

[0077] For each 2D configuration of the runways of an aerodrome (figures 7A, 7B, 7C, 7D), it is necessary to determine the number of primary cameras 18 required and the positioning of the primary cameras 18. In each configuration, each runway is arranged or covered by the angular opening of a primary camera 18. A given primary camera can thus cover several ends E1, E2 of runways V1, V2.

[0078] In the configuration of Figure 7A, the first primary angular aperture Pa of a first primary camera 18a covers the two ends El of the two tracks VI, V2 while the second primary angular aperture Pb of the second primary camera 18b covers the two ends E2 of the two tracks VI, V2. Thus, in a parallel track configuration, only two primary cameras 18 are necessary.

[0079] In the configuration of FIG. 7B, it is observed that it is necessary to have three primary cameras 18, the first primary angular aperture Pa of a first primary camera 18a covers the two ends E2 of the two tracks VI, V2 while the second primary angular aperture Pb of the second primary camera 18b covers one end El of the track VI and the third primary angular aperture Pc of the third primary camera 18c covers one end El of the track V2.

[0080] In the configuration of Figure 7C, it is observed that two primary cameras 18 are necessary. The first primary angular aperture Pa of a first primary camera 18a covers the two ends El of the two tracks VI, V2 while the second primary angular aperture Pb of the second primary camera 18b covers the two ends E2 of the two tracks VI, V2.

[0081] In the configuration of FIG. 7D, it is observed that it is necessary to have four primary cameras 18. In this configuration, each primary angular aperture of a primary camera covers a single end E1, E2 of a track V1, V2.

[0082] In the configurations shown in [Fig.7], a secondary camera 16 is used to track an aircraft from the end E1, E2 where it was detected. For example, when the aircraft is detected in the landing / takeoff phase in one of the images from a primary camera 18, the secondary camera 16 tracks the aircraft during landing / takeoff on the relevant runway V1, V2.

[0083] Each runway VI, V2 is associated with a primary camera 18 for detecting an aircraft in the takeoff / landing phase at each of its ends E1, E2. Each position of a primary angular aperture Px of a primary camera 18 is associated with a first tracking start position for the takeoff / landing phase for the secondary camera 16. This first tracking start position is such that the secondary angular aperture 17 of the secondary camera 16 intercepts at least partially the primary angular aperture of the primary camera 18 achieving a positive detection. In practice, there are as many first positions as there are primary cameras 18. Each secondary camera is associated with a second tracking end position which can be fixed for a runway configuration.It can also be a function of a positive identification of an aircraft, thus leading to stopping the tracking of the aircraft by the secondary camera 16, which can for example take a waiting position in the first tracking position at the level of a runway VI, V2.

[0084] In the present document, a system comprising a single secondary camera is presented. However, it is understood that the present disclosure, in all its characteristics, also applies to a system comprising at least one secondary camera and therefore capable of comprising a second secondary camera. Such an additional secondary camera could be used simultaneously with the first secondary camera to position itself in a first tracking or waiting position while the first camera tracks the trajectory of an aircraft landing. This configuration would be particularly interesting when the aerodrome comprises a larger number of runways, for example more than two, which would make it possible to manage more air traffic with the system.

[0085] Preferably, the primary angular aperture Px, Pa, Pb of each primary camera is configured to comprise a zone 46 for junction of a taxiway 44 to a runway VI. Thus, the primary angular aperture Px of a primary camera 18 comprises both an end E1, E2 of the runway VI and said junction zone 46, which makes it possible to identify that an aircraft is entering or leaving the runway VI ([Fig.8]).

[0086] The positioning of the optronic system around the tracks is carried out according to the maximum range of the secondary camera 16. The reading being done on the central third of each track, the optronic system will then be placed on the intersection of two discs of radius equal to the maximum range of the secondary camera 16, in the case of a two-track configuration. The two-track configuration is the most common. Other parameters can be taken into account such as the relief (because the tracks are not always flat), the masks (buildings, trees, etc.) which reduce the possibilities within this intersection.

[0087] The method described below in the figures is intended to be implemented using an optronic system for monitoring air traffic, in particular for an uncontrolled aerodrome, comprising at least one secondary camera 16 having a secondary angular aperture 17 and at least two static primary cameras 18 having a primary angular aperture 18x which is greater than the secondary angular aperture 17 of the secondary camera 16, said at least two primary cameras being arranged around the same longitudinal axis on which said secondary camera is mounted to be movable in rotation. At least two primary cameras 18 are necessary to confirm the trajectory of an aircraft. The optronic system may comprise all or part of the characteristics of the optronic system described with reference to Figures 1 to 8.However, only one can be used if one only wishes to determine the behavior of an aircraft without having confirmation of its status (it landed, touched down and departed or it flew over the aerodrome at low altitude) as will appear below.

[0088] We now refer to [Fig.9] which comprises a part A which represents an image 100 of a zone of space observed through a primary angular aperture of a first primary camera oriented towards a first end of a runway VI and which can be described as a primary camera for the approach phase and part B represents an image 102 of a space area observed through an angular opening of a second primary camera oriented towards a second end of the runway VI and which can be described as a primary runway exit camera.

[0089] The image of Figure 9A includes several areas that are intended to serve for the purpose of providing an indication of an aircraft approaching runway VI. The image 102 of Figure 9B includes several areas that are intended to serve for the purpose of confirming the status of the aircraft that has entered the approach phase in the image of Figure 9A.

[0090] As can be seen, the first primary camera is oriented so that its primary angular aperture includes a first end of the VL track. The second primary camera is oriented so that its primary angular aperture includes a second end of the track Figure 9B.

[0091] In the image of FIG. 9A, we observe the presence of a rectangle 104 whose dimension is smaller than the primary angular aperture of the first camera. This rectangle 104 therefore corresponds to an analysis zone, that is to say to a zone in which the image processing will be carried out to detect the presence of objects related to an aircraft.

[0092] This analysis zone 104 corresponding to a reduced part of the primary angular aperture makes it possible to make digital processing compatible with a real-time analysis objective. This rectangle 104 comprises an approach zone 106 extending by an end-of-approach region 108. The approach zone has the shape of a corridor delimited below by a first low line arranged 106a above the runway and above by a second high line 106b arranged above the first line.

[0093] In order to determine the positioning of the first primary camera and more practically its azimuthal orientation, the method comprises a step of determining a set of possible approach trajectories on the runway (not visible). After this step, the position of the primary camera is determined so that its primary angular aperture includes said set of possible trajectories. In practice, the angular aperture of each primary camera is determined so as to also include a junction zone 107a of a taxiway 107 with the runway so as to be able to control the runway entries and exits corresponding to an upcoming takeoff and a completed landing. The taxiway comprises a zone 118 formed on a taxiway connected to the runway. This zone will be better described in relation to [Fig.l 1].

[0094] The analysis zone 104 is positioned so as to be located above the horizon, preferably grazing, and to include all of said trajectories approach to avoid including objects moving on the ground such as trees which undergo regular movements.

[0095] Thus, each approach zone 106 is associated with an end-of-approach region 108 which is located in the approach zone 106. This end-of-approach region 108 corresponds to the zone in which the detection of an object having a size compatible with that of an aircraft triggers the implementation of a confirmation step that the identified flying object corresponds to an aircraft. Prior to the implementation of the confirmation step, the flying objects compatible with an aircraft size are tracked in real time in the approach zone. The real-time tracking will be explained below with reference to FIGS. 12 to 14.

[0096] The method according to the present document preferably also comprises the steps of: - Identification of possible runway exit trajectories of an aircraft at the second end of the runway; these runway exit trajectories correspond to all possible trajectories after the aircraft has passed a first end of the runway, passing a middle part of said runway. It is understood that there is no bijection between an approach trajectory and a given behavior of the aircraft. In other words, an aircraft with a given approach trajectory may well correspond to one of the three possibilities of runway exit trajectories mentioned above, namely the aircraft has landed, the aircraft has touched down and taken off again and the aircraft has flown over the runway at low altitude; - classification of said possible trajectories into three possible behaviors, a first behavior corresponding to an actual landing, a second behavior corresponding to a runway touchdown without landing and the third behavior corresponding to an overflight of the runway at low altitude, - Determination of a position of the second primary camera so that its primary angular aperture includes all possible runway exit trajectories, - Determination, in the primary angular aperture of the second camera, of three zones, a first zone 110 at the end of the runway corresponding to the first behavior, a second 112 at the end of the runway corresponding to the second behavior and a third zone 114 at the end of the runway corresponding to the third behavior (figure 9B).

[0097] We observe the presence of a large zone 116 encompassing said three zones 110, 112, 114, this zone corresponds to that on which the real-time image processing analysis is carried out (see figures 12 to 14).

[0098] Thus, for each primary camera, there is a first set of approach zones and region for the approach phase and a second set of zones for confirmation of the status of the aircraft after entering the approach phase. This is necessary since each end of the runway can be used for takeoff and landing depending on the prevailing wind direction relative to the runway. The angular aperture of a primary camera must be such that the primary camera must be able to function as a primary camera for detecting an approach or as a primary camera for confirming the status of an aircraft.

[0099] [Fig. 10] illustrates another runway configuration which includes the same zones as those described in Figure 9A. However, it is understood that the shape of each of the zones is different since it is each time a function of the three-dimensional configuration of the runways of the aerodrome concerned.

[0100] [Fig. 11] illustrates a zone 118 formed on a taxiway connected to the runway. This zone 118 can be placed at the intersection of the taxiway and the runway or be positioned on the taxiway as is the case here. It can be seen that this zone comprises two longitudinal end regions 120a, 120b making it possible to determine the passage of an aircraft in one direction or the other. Depending on whether the aircraft passes through zone 120a or zone 120b first and then passes into the other zone, it can be understood that it is possible to detect the direction of movement of the aircraft and then to verify that it is traveling in the correct direction as prescribed by the rules in force.

[0101] For each image obtained by one and the other of the primary cameras, the following processing is carried out. In practice, the method for detecting an aircraft is implemented from the images of all the primary cameras 18. In this way, the landing detections are carried out regardless of the landing direction, which is particularly true when the wind is light where the choice of the landing direction belongs to the pilot. The primary camera 18 first detects an aircraft in the approach phase then gives the indication to the secondary camera 16 of the place where it must position itself.

[0102] Firstly, each image acquired by a primary camera undergoes processing by an attenuation filter SI, such as for example a Gaussian blur, which makes it possible to standardize the image. This first step makes it possible to eliminate small objects from the image which are therefore considered here as noise. However, care will be taken to ensure that the attenuation filter applied is sufficiently weak so as not to affect the aircraft detection resolution. For this, an empirical adjustment is possible on the images acquired by each primary camera in its desired position relative to one end of the runway.

[0103] In a step S2, for a given image 121 at a given time t: - take the average of x images 119 temporally preceding the given image and obtain an averaged image 123 - Subtract the given image from the averaged image and get a resulting image 125.

[0104] The resulting image thus comprises only the parts which have undergone a displacement compared to the average of the previous images 123 ([Fig. 12]). Only the parts of the image greater than a threshold value are retained. These parts therefore correspond to parts which have moved. It is understood that the greater the number x of images taken into account, the more the resulting image will comprise zones greater than the threshold value. This principle is illustrated in [Fig. 13] which shows three cases A, B and C each comprising two images, a first image 122 corresponds to the resulting image and a second image 124 corresponding to the resulting image after application of the threshold. In case A, the number of images x taken into account is 10, in case B, x is equal to 100 and in case C x is equal to 1000.

[0105] Each black and white output image undergoes a step S3 of closing the contours which can advantageously be carried out by contour dilation. This mathematical function is well known to those skilled in the art and will not be described in further detail. The dilation must be carried out sufficiently to avoid increasing the size of the object too significantly. An iteration may be carried out

[0106] In a step S4, objects having a size incompatible with an aircraft are eliminated. It is understood that the size criterion does not make it possible to distinguish a bird caught in the field of a primary camera at a distance such that its size becomes compatible with the size of an aircraft located at a greater distance from the primary camera.

[0107] The processing carried out through steps S1 to S4 could be carried out on all the images acquired by the primary camera. However, this would lead to the storage of a large amount of data. To this end, steps S1 to S4 are carried out on one image out of k, k being able to take a value of 3 for example. The Im-S4 images obtained at the end of step S4 are stored in a database and kept to carry out step S5. Obviously, it is not necessary to keep all the Im-S4 images. In practice, N Im-S4 images are stored, the choice of N being made to be able to keep sufficient history. Thus, it will be possible to keep a number of Im-S4 images of at least 4 when the primary camera has an acquisition rate of 25 images per second.

[0108] In a step S5, an object detection is carried out in the approach region of the image Im-S4. Thus, each processing S1-S4 is associated with an end processing consisting of verifying the presence or absence of an object compatible with an aircraft in the approach zone 108.

[0109] In the event of a positive detection of an object in the approach region 108, it must be determined whether or not the detected object is an aircraft.

[0110] For this purpose, in a step S6, an indication is provided that an aircraft is in the approach phase. This step S6 makes it possible to distinguish between aircraft-type objects and other objects. Verifying the following conditions makes it possible to ensure that an aircraft is indeed in the approach phase for landing: a. At least one object was identified in an approach region of the last Im-S4a image obtained, b. At least one object has been detected in the approach zone and on at least k Im-S4 j images (i varying from 1 to k) temporally preceding the Im-S4a image for which an object was detected in the end-of-approach region, k being less than or equal to N. k can be equal to 3. c. there are at least k hn-S4i images comprising at least one object of a size compatible with that of an aircraft and the abscissa of each of the objects is greater (or less depending on whether the object assumed to be an aircraft arrives towards one end or the other of runway VI) than the abscissa of the object detected in the end-of-approach region, • this condition ensures that the object follows a continuous progression from left to right or from right to left. The origin of the abscissa is determined at one end of the track. d. determine all possible paths between the objects of successive Im-S4 j images (i varying from 1 to k) and leading to the object identified on Im-S4 a image, then determine whether the trajectory follows a straight line or not. This last step can be carried out by determining a correlation coefficient r2 which should preferably be greater than 0.9.

[0111] [Fig. 15] illustrates the objects detected on the Im-S4 j images and the different possible paths. It can be seen that steps a) to c) are verified and step d is only verified for path 128, paths 132 not being sufficiently linear. [Fig. 15] also illustrates the direction of approach of the aircraft with arrow 134.

Claims

1. Claims Method for detecting an aircraft in the landing phase on an aerodrome, in particular an uncontrolled aerodrome, the aerodrome comprising at least one runway (VI) having at least two ends (El, E2), and by means of an optronic system comprising at least one primary camera of which a primary angular aperture is oriented towards a first end (El) of the runway, the method comprising the steps: - Determination of a set of possible approach trajectories on said at least one runway (V1), - Determining a position of said at least one primary camera so that its primary angular aperture includes said set of possible trajectories, - Determination, in the primary angular aperture, of an analysis zone shaped so as to include all of said approach trajectories and preferably located above the horizon; - Determination of an end-of-approach region in the analysis zone; - Carrying out, in the said analysis zone, a detection of objects having a size compatible with that of an aircraft, - Determination of the presence or absence, in the approach region, of an object compatible with an aircraft, and where appropriate analysis of the path of the detected object by comparison of its current position with a history of the positions of objects detected in the analysis zone and included in the database, in which the analysis zone comprises an approach zone delimited below by a first low line arranged above the runway and above by a second high line arranged above the first line, the approach zone being connected to the end of approach region, and in which the indication that an aircraft is in the approach phase is carried out by verifying that:

2. a. At least one object has been detected in the approach zone and on at least k Im-S4 i5 i images varying from 1 to k, temporally preceding the Im-S4 a image for which an object was detected in the end-of-approach region, b. there are at least k Im-S4 images; comprising at least one object of a size compatible with that of an aircraft and the abscissa of each of the objects is greater, or less depending on whether the object assumed to be an aircraft, arrives towards one end or the other of runway VI, than the abscissa of the object detected in the end of approach region, c. determine all possible paths between the objects of successive Im-S4 j images, i varying from 1 to k, and leading to the object identified on the Im-S4 a image, then we validate whether a trajectory follows a straight line or not. Method according to one of the preceding claims, in which the optronic system comprises at least one second primary camera whose primary angular aperture is oriented towards a second end (E1, E2) of the track, the method comprising: - identification of possible runway exit trajectories for an aircraft at the second end of the runway; - the classification of said possible trajectories into three possible behaviors, a first behavior corresponding to an actual landing, a second behavior corresponding to a runway touchdown without landing and the third behavior corresponding to an overflight of the runway at low altitude, - Determination of a position of the second primary camera so that its primary angular aperture includes all possible runway exit trajectories, - Determination, in the primary angular aperture of the second camera, of three zones, a first end-of-runway zone corresponding to the first behavior, a second end-of-runway zone corresponding to the second behavior and a third end-of-runway zone corresponding to the third behavior.

3. Method according to one of the preceding claims, in which it comprises: - Continuous recording of the angular aperture of the primary camera, - For a given image at a given time t: • taking the average of x images temporally preceding the given image and obtaining an averaged image, • Subtracting the given image from the averaged image.

4. Method according to the preceding claim, in which a dilation step is applied to the given image.

5. Method according to one of the preceding claims, in which the position of the primary camera is determined so that its primary angular aperture comprises an intersection of said at least one runway with a taxiway.

6. Method according to the preceding claim, in which it comprises determining an intersection region in the primary angular aperture of the primary camera, this intersection region encompassing the intersection of the runway with the taxiway.

7. The method of claim 1, wherein the first low line has an inclination of a non-zero angle α relative to the axis of said at least one track.

8. Method according to the preceding claim, in which a is greater than or equal to 3°.

9. Method according to one of the two preceding claims, in which the second upper line has an inclination of an angle [3 greater than the angle a, the angle [3 being determined as corresponding to the maximum possible angle of arrival of an aircraft on said at least one runway.

10. Method according to the preceding claim, in which the optronic system comprises a secondary camera movable in rotation around a vertical axis so that its optical axis can follow a moving aircraft, the method comprising a subsequent step of tracking an aircraft after indicating the presence of an aircraft in the approach region.

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