Air traffic monitoring method

Abstract

This document relates to a method for detecting an aircraft during its landing phase at an aerodrome, particularly an uncontrolled one, 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 whose primary angular aperture is directed towards a first end (E1) of the runway. The method comprises determining the presence or absence, in an approach area, of an object compatible with an aircraft, and, if so, analyzing the trajectory of the detected object by comparing its current position with a history of the positions of objects detected in an analysis area. Abstract figure: Figure 14

Description

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

[0001] This disclosure falls within the field of air traffic monitoring systems and processes, more particularly for uncontrolled aerodromes. Previous technique

[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 type offers distinct characteristics and procedures for pilots and flight 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 the instructions issued by the controllers for their movements within the aerodrome and 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 aerodromes do not have a control tower or air traffic controllers. Pilots operating at these aerodromes use a specific radio frequency to communicate with each other and share information about movements at the aerodrome. They are responsible for their own safety and for managing air traffic, adhering to standard procedures and exercising heightened vigilance to avoid potential conflicts with other aircraft. Uncontrolled aerodromes are generally equipped with visual aids such as beacons, runway identification signs, and ground markings to facilitate pilot navigation.

[0005] Uncontrolled aerodromes are far more numerous than controlled aerodromes, since 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 mainly for general aviation, recreational flights, agricultural operations, training flights, etc. These aerodromes can be small Local facilities, training airfields, air sports airfields, emergency airfields, and many others. 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) or not.

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

[0009] AFIS service is generally provided by qualified personnel called Flight Information Service Officers (FISOs). FISOs are responsible for providing information and advice to pilots operating at and around the aerodrome. Their primary role is to ensure the safety of flight operations by providing relevant information on weather conditions, local air traffic, aerodrome procedures, and other information useful 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 advice and instructions to pilots, particularly for ground movements, takeoffs and landings, while coordinating aircraft activities at the aerodrome.

[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 aerodromes are being transformed into uncontrolled aerodromes due to insufficient air traffic and / or increasing operating costs (standards to be met, ...).

[0013] However, the passage 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 (condition of the runways, fire, accident, etc.,) - arranging flight times to optimize the noise around the aerodrome.

[0014] It is therefore understandable that aircraft detection at 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 sector, with ranges of a few tens of meters, which requires the installation of equipment at each exit of an aerodrome taxiway, - Cooperative surveillance systems of the ADS-B type (Automatic Dependent Surveillance-Broadcast), but which equip only a very limited part of the aerodrome aircraft fleet (on the order of 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 over 5,700 kg or those authorized to carry more than 19 passengers, which do not constitute the bulk of the fleet of aircraft using uncontrolled aerodromes.

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

[0016] Moreover, none of the current systems allow for 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 wide variability of situations at aerodromes prevents the development of a sufficiently reliable algorithm for detecting an aircraft and only an aircraft. Among the factors that impact detection are: - The movement of trees in strong winds, - The movement of grasses in average wind, - Shadows of clouds moving across the ground, - Clouds of smoke, - Cars moving within the camera's field of view, - Birds, which, depending on their location, have the apparent size of a airplane for the camera.

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

[0019] This document relates to a method for detecting an aircraft in the landing phase at an aerodrome, in particular an uncontrolled aerodrome, 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 having a primary angular aperture 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 for said at least one primary camera such that its primary angular aperture encompasses said set of possible trajectories, - Determination, within the primary angular aperture, of a conformal analysis zone so as to understand all of said approach trajectories and preferably located above the horizon; - Determination of an end-of-approach region within the analysis area; - Implementation, within the aforementioned analysis zone, of object detection for objects of a size compatible with that of an aircraft, - Determination of the presence or absence, in the approach area, of an object compatible with an aircraft, and if so, analysis of the path of the detected object by comparing its current position with a history of the positions of objects detected in the analysis area and included in the database.

[0020] In practice, over at least one day or several, aircraft flights are recorded in such a way as to identify all possible trajectories. At least one hundred flights are necessary to ensure that all possible trajectories are recorded. It is understood that the set of approach trajectories is a set that allows the approach trajectories to be positioned in three dimensions relative to the runway.

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

[0022] According to another feature, the indication that an aircraft is on approach can be made by verifying that: a. At least one object was detected in the approach zone and on at least k Im-S4 images; i ranging 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 Im-S4i images including at least one object of a size compatible with that of an aircraft and the abscissa of each of the objects is greater than (or less than depending on whether the object assumed to be an aircraft is approaching 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 path follows a straight line approximately or not.

[0023] According to this document, the three aforementioned conditions must have been met in order to confirm that an aircraft is indeed in the approach area. The last

[0024]

[0025]

[0026]

[0027]

[0028] A linear regression step confirms the non-chaotic nature 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 of a size comparable to that of an aircraft, due, for example, to a location closer to the aircraft. The optronic system may include at least one second primary camera whose primary angular aperture is directed 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 touch-and-go without landing, and a third behavior corresponding to a low-altitude flyover of the runway. - Determining the position of the second primary camera so that its primary angular aperture encompasses all possible off-track trajectories, - Determination, in the primary angular aperture of the second camera, of three zones, a first end-of-track zone corresponding to the first behavior, a second end-of-track zone corresponding to the second behavior and a third end-of-track zone corresponding to the third behavior. Based on an aircraft's approach path, it is difficult to determine whether the aircraft will actually land, merely touch down, or simply fly over the runway at low altitude. Since distinguishing between these three scenarios is not possible using only the approach path, an analysis must be performed using a second primary camera positioned at the far end of the runway. Obviously, we understand that the first primary camera can play the role of the second primary camera depending on the direction of aircraft landings. A runway exit trajectory is here a trajectory for exiting the second end observation zone of the runway. The process may also include: - A continuous recording of the angular aperture of the primary camera, - For a given image at a given instant t: • calculate the average of x images preceding the given image over time and obtain an averaged image, • Subtract the given image from the averaged image.

[0029] The average of the previous x images is calculated pixel by pixel. The number x of images used to calculate the average is significant and will be determined by successive iterations.

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

[0031] This expansion step allows the contours to be closed. Preferably, objects with a surface area greater than a predetermined size are eliminated.

[0032] The position of the primary camera can be determined so that its primary angular aperture includes an intersection of said at least one track with a traffic lane.

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

[0034] The method may include determining an intersection region in the primary angular aperture of the primary camera, this intersection region encompassing the intersection of the track with the traffic lane.

[0035] The analysis area may include an approach area 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 area being connected to the end-of-approach area.

[0036] The first lower line may have an inclination of a non-zero angle α with respect 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 a competent aviation authority for the aerodrome in question. In France, the minimum value is 3° with a possible deviation of 0.5°.

[0038] This greater inclination of at least 3° relative to the runway axis makes it possible to remove part of the scenery which could 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 a standard approach.

[0041] The optronic system used with the method described above may include a secondary camera that rotates about a vertical axis so that its optical axis can track a moving aircraft, the method including a subsequent step of tracking an aircraft after the presence of an aircraft has been indicated in the approach region. Brief description of the drawings

[0042] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0043] [Fig-1] illustrates an optronic system according to this document in a non-deployed position in Figure IA and in a deployed position and ready for use in Figure IB;

[0044] [Fig.2] is a schematic perspective view of an optronic system according to this document in a non-deployed position, the system being shown without the support elements visible in [Fig.1];

[0045] [Fig.3] is a schematic perspective view of a portion of the mast supporting a plurality of primary cameras, oriented from bottom to top

[0046] [Fig.4] is a larger-scale view of the means of movement of 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 from top to bottom;

[0048] [Fig.6] represents a logic diagram of the 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 aerodrome;

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

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

[0052] [Fig.11] is a larger scale image of part of [Fig.10];

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

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

[0055] [Fig. 14] is a flowchart of the steps for 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 implementation methods

[0057] Reference is now made to [Fig. 1], which represents a system 10 according to this 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 that is movable and rotatable about its longitudinal axis, and at least two primary cameras 18 (best seen in [Fig. 2]) that are fixed. By movable and rotatable camera and fixed camera, it is understood that in operation the camera is capable of moving, and by static or fixed camera, it is understood that the camera is fixed in operation, that is, when the system is in use. Obviously, for adjusting the positioning of the primary cameras 18, they can be connected to suitable means of movement, as will be seen below.

[0058] The mast 14 can advantageously be telescopic, as illustrated in Figures 1A and 1B, and can thus comprise a plurality of tubular segments 15 arranged one inside the other. The system 10 is here surrounded by a protective enclosure 20 designed to prevent damage by unauthorized persons (intrusions) or due to aircraft impacts (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 for rotation between a support position and a standby position.

[0059] Each camera 16, 18 includes its own angular aperture. The secondary camera 16 includes a secondary angular aperture 17. The system 10 includes 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 denoted 18a, the second primary camera is denoted 18b, the third primary camera is denoted 18c, etc. Each angular aperture is denoted 18x where x is a letter designating the primary camera 18x. Each primary camera 18x includes 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 at any type of uncontrolled aerodrome. It is thus suitable for installation at uncontrolled aerodromes with a runway configuration of VI, V2 as shown in Figures 7A, 7B, 7C, 7D. It will be readily understood from the description that the invention is ap Applicable to any type of aerodrome with one or more runways. The 2D configuration of the runways, that is, the number of runways and the two-dimensional arrangement of their axes relative to each other, determines the number of primary cameras required and their positioning. In practice, when the aerodrome has more than two runways, it is preferable to use more than one optronic system. In such a situation, an optronic system will advantageously include 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 runways beyond these 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 mounted on 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 can be seen 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 can have a frustoconical shape, preferably with a cross-section that narrows towards the secondary camera 16.

[0063] Each primary camera 18 can 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 means of movement may be motors illustrated in 22 and which may be arranged inside the mast 14 so as to protect them.

[0065] The movement means for 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 fixed to a ring 26 carried by the mast, and the other end carries the movement means for the optical axis of a primary camera 18 ([Fig. 5]). The movement means for a primary camera 18 include means for elevation movement, azimuth movement means, and translational movement means relative to the longitudinal axis L ([Fig. 4]).

[0066] The means for moving upwards comprise a yoke 28 fixed to the primary camera 18 and an arm 30 articulated for rotation on the yoke 28. The articulation is made along a horizontal axis 32, that is to say an axis perpendicular to the longitudinal axis tudinal and positioned so as to allow adjustment of the orientation of the axis of the primary camera 18 with respect to a horizontal plane.

[0067] The azimuth movement means include the arm 30 which is mounted for rotation on a member 32 around a vertical axis 34 parallel to the longitudinal axis L.

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

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

[0070] As can be seen in [Fig. 5], the ring 26 includes connectors, preferably a plurality of triplets of 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 one connector C3 is provided for the power supply of a primary camera 18. These connectors allow the video and power cables of a primary camera 18 to be connected to a static support of the mast 14.

[0071] According to this disclosure, the system 10 may include means for moving 40, in particular for rotating 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 achieve dynamic tracking of an aircraft during landing or takeoff, and means for controlling the means 42 of the means for moving 40. The means for controlling 42 are connected to means for recognizing and tracking an aircraft in a primary aperture Px.Thus, the control means 42, in communication / liaison with the reconnaissance and tracking means 43, are informed of the aircraft's positioning within a static primary angular aperture Px and enable the actuating of the movement means 42 to perform tracking of the aircraft in the secondary angular aperture 17 – moving in rotation with the secondary camera 16 – to allow for aircraft identification. The movement means 40 of the secondary camera 16 may also include means for moving the optical axis of the secondary camera 16 in elevation.

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

[0073] Aircraft identification means are means for identifying the aircraft, that is, means for recognizing the characters of a registration plate located on the aircraft. Recognition and tracking means 43 refer to 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 SCMOS camera with a 12° - 4° field of view and a continuous 3x optical zoom ranging from 200 to 600 mm. It may have a low-light capability (ISO > 400,000). Each primary camera 18 may be a SONY FCB-ER8550 4K CMOS camera with a 4.4-88 mm field of view and a 60° - 3.5° field of view, and a continuous 20x optical zoom between 4.4 and 88 mm.

[0075] Reference is now made 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 intersect, the tracks VI, V2 forming an angle of less than 90°, in this case approximately 40°. In Figure 7C, the configuration is such that two tracks VI, V2 intersect each other at an angle of less than 90°, in this case approximately 30°. In Figure 7D, the tracks VI, V2 are perpendicular to each other and intersect, in this case substantially at their midpoint.

[0076] In the various 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 either 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 El, E2 of runways VI, 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 required.

[0079] In the configuration of Figure 7B, it can be seen that three primary cameras 18 are required; the first primary angular aperture Pa of a first primary camera 18a covers both 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 track VI and the third primary angular aperture Pc of the third primary camera 18c covers one end El of track V2.

[0080] In the configuration of Figure 7C, it can be seen that two primary cameras 18 are required. 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 Figure 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 only one end El, E2 of a track VI, V2.

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

[0083] Each runway VI, V2 is associated with a primary camera 18 for detecting an aircraft during takeoff / landing 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 at least partially intercepts the primary angular aperture of the primary camera 18, thus 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 given runway configuration.It can also be a function of a positive identification of an aircraft, thus leading to the stopping of the aircraft tracking 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] This document presents a system comprising a single secondary camera. However, it is understood that this disclosure, in all its features, also applies to a system comprising at least one secondary camera and therefore potentially including a second secondary camera. Such an additional secondary camera could be used simultaneously with the first secondary camera to position itself in an initial tracking or holding position while the first camera tracks the trajectory of a landing aircraft. This configuration would be particularly advantageous when the aerodrome has a larger number of runways, for example, more than two, which would allow the system to handle a larger volume of air traffic.

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

[0086] The positioning of the optronic system around the runways is determined based on the maximum range of the secondary camera 16. Since the reading is taken on the central third of each runway, the optronic system will be placed at the intersection of two disks with a radius equal to the maximum range of the secondary camera 16, in the case of a two-runway configuration. The two-runway configuration is the most common. Other parameters can be taken into account, such as the terrain (since the runways are not always flat), and obstructions (buildings, trees, etc.) that reduce the possibilities within this intersection.

[0087] The method described below in the figures is intended to be implemented using an optronic system for air traffic monitoring, 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 that 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 for rotational movement. At least two primary cameras 18 are required to confirm the trajectory of an aircraft. The optronic system may include all or part of the features of the optronic system described with reference to Figures 1 to 8.However, only one can be used if one wishes solely to determine the behavior of an aircraft without having confirmation of its status (it landed, touched down and took off again, or it flew over the aerodrome at low altitude) as will appear below.

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

[0089] The image in Figure 9A includes several areas intended to provide an approach indication for an aircraft on runway VI. Image 102 of the Figure 9B includes several areas which are intended to serve to confirm the status of the aircraft that has passed into 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 track VI. The second primary camera is oriented so that its primary angular aperture includes a second end of track Figure 9B.

[0091] In the image in Figure 9A, a rectangle 104 can be seen, the dimensions of which are smaller than the primary angular aperture of the first camera. This rectangle 104 therefore corresponds to an analysis zone, that is to say, a zone in which image processing will be carried out to detect the presence of objects resembling an aircraft.

[0092] This analysis zone 104, corresponding to a reduced portion of the primary angular aperture, makes it possible to ensure compatibility between digital processing and a real-time analysis objective. This rectangle 104 comprises an approach zone 106 extending into 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 includes 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 encompasses 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 in order to control runway entries and exits corresponding to an upcoming takeoff and a completed landing. The taxiway includes a zone 118 formed on a taxiway connected to the runway. This zone will be better described in relation to [Fig. 1 1].

[0094] The analysis zone 104 is positioned so as to be located above the horizon, preferably at a low angle, and to include all of said approach trajectories in order 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 located within the approach zone 106. This end-of-approach region 108 corresponds to the area in which the detection of an object of a size consistent with that of an aircraft triggers the implementation of a confirmation step that the identified flying object is indeed an aircraft. Prior to the implementation of During the confirmation stage, flying objects compatible with an aircraft size are tracked in real time within the approach zone. Real-time tracking will be explained below with reference to Figures 12 to 14.

[0096] The process according to this document preferably also includes the steps of: - Identification of possible runway excursion trajectories for an aircraft at the second end of the runway; these runway excursion trajectories correspond to all possible trajectories after the aircraft has passed the first end of the runway, and the mid-section of said runway. It is understood that there is no one-to-one correspondence between an approach trajectory and a given aircraft behavior. In other words, an aircraft with a given approach trajectory can very well correspond to one of the three possible runway excursion trajectories mentioned previously, namely the aircraft landed, the aircraft touched down and took off again, and the aircraft flew 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 touch-and-go without landing, and a third behavior corresponding to a low-altitude flyover of the runway; - Determination of a position for the second primary camera such that its primary angular aperture encompasses all possible runway exit trajectories. - Determination, in the primary angular opening of the second camera, of three zones, a first zone 110 at the end of the track corresponding to the first behavior, a second 112 at the end of the track corresponding to the second behavior and a third zone 114 at the end of the track corresponding to the third behavior (figure 9B).

[0097] We observe the presence of a large area 116 encompassing the said three areas 110, 112, 114, this area 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 regions for the approach phase and a second set of zones for confirming the aircraft's status after it has entered the approach phase. This is necessary because each runway end 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 can function as either an approach detection camera or an aircraft status confirmation camera.

[0099] Fig. 10 illustrates another runway configuration which includes the same zones as those described in Figure 9A. However, it is clear 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] Figure 11 illustrates a zone 118 formed on a taxiway connected to the runway. This zone 118 can be located at the intersection of the taxiway and the runway or positioned on the taxiway itself, as is the case here. It can be seen that this zone comprises two longitudinal end regions 120a and 120b, which allow for the determination of whether an aircraft is traveling in one direction or the other. Depending on whether the aircraft passes through zone 120a or zone 120b first and then through the other zone, it is possible to detect the aircraft's direction of travel and then verify that it is traveling in the correct direction as prescribed by the applicable rules.

[0101] For each image obtained by either of the primary cameras, the following processing is performed. In practice, the aircraft detection process is implemented using the images from all the primary cameras 18. In this way, landing detections are performed regardless of the landing direction, which is particularly true when the wind is light and the choice of landing direction belongs to the pilot. The primary camera 18 first detects an aircraft on approach, then provides the secondary camera 16 with the location where it should position itself.

[0102] First, each image acquired by a primary camera undergoes processing with an SI attenuation filter, such as Gaussian blur, to smooth out the image. This first step eliminates small objects from the image, which are therefore considered noise. However, care must be taken to ensure that the applied attenuation filter is sufficiently weak so as not to affect the aircraft detection resolution. To achieve this, 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: - calculate the average of x images 119 preceding the given image temporally and obtain an averaged image 123 - Subtract the given image from the averaged image and obtain a resulting image 125.

[0104] The resulting image thus includes only the parts that have been displaced relative to the average of the previous images 123 ([Fig. 12]). Only the parts of the image exceeding a threshold value are retained. These parts therefore correspond to areas that have moved. It is understood that the larger the number x of images taken into account, the more areas the resulting image will contain. 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, corresponds to the resulting image after the threshold has been applied. In case A, the number of images x considered 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 contour closing step S3, which can advantageously be performed 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 performed sufficiently to avoid excessively increasing the size of the object. An iteration may be performed

[0106] In a step S4, objects whose size is incompatible with an aircraft are eliminated. It is understood that the size criterion does not allow for the distinction of a bird captured within the field of view 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 performed in steps SI 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 SI to S4 are performed on one image out of k, where k can take a value of 3, for example. The Im-S4 images obtained at the end of step S4 are stored in a database and retained to perform step S5. Obviously, it is not necessary to retain all the Im-S4 images. In practice, N Im-S4 images are stored, the choice of N being made to ensure sufficient historical data retention. Thus, at least 4 Im-S4 images can be retained when the primary camera has an acquisition rate of 25 frames per second.

[0108] In a step S5, an object detection is performed in the approach region of the Im-S4 image. Thus, each S1-S4 processing is associated with a final processing consisting of checking 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 is necessary to determine whether the detected object is an aircraft or not.

[0110] To this end, in step S6, an indication is provided that an aircraft is on approach. This step S6 makes it possible to distinguish between aircraft-type objects and other objects. Verification of the following conditions ensures that an aircraft is indeed on approach to land: a. At least one object has been identified in an approach region of the last Im-S4a image obtained, b. At least one object was detected in the approach zone and on at least k [YES] Im-S4j 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 Im-S4i images including at least one object of a size compatible with that of an aircraft and the abscissa of each of the objects is greater than (or less than depending on whether the object assumed to be an aircraft is approaching 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 right to left. The origin of the x-coordinate is determined at one end of the track. d. Determine all possible paths between the objects in successive Im-S4j images (i ranging from 1 to k) that lead to the object identified in Im-S4a image, and then determine whether the path follows a straight line approximately. This last step can be performed by determining a correlation coefficient r2, which should preferably be greater than 0.9. Figure 15 illustrates the objects detected in the Im-S4j images and the different possible paths. It can be seen that steps a) to c) are verified, and step d is verified only for path 128, as paths 132 are not sufficiently linear. Figure 15 also illustrates the aircraft's approach direction with arrow 134.

Claims

Claims

1. Method for detecting an aircraft in the landing phase on an aerodrome, in particular an uncontrolled one, 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 (VI), - 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 said analysis zone, a detection of objects having a size compatible with that of an aircraft, - Determining the presence or not, in the 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 the analysis zone and included in the database.

2. Method according to one of the preceding claims, in which the indication that an aircraft is in the approach phase is carried out by verifying that: a. At least one object has been detected in the approach zone and on at least k Im-S4j 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 Im-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 the runway VI) at the abscissa of the object detected in the end of approach region, c. determine all the possible paths between the objects of the successive Im-S4j images (i varying from 1 to k) and leading to the object identified on the Im-S4a image, then we validate that a trajectory follows substantially or not a straight line.

3. 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 (El, E2) of the runway, the method comprising: - the identification of the possible runway exit trajectories of 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 runway end zone corresponding to the first behavior, a second runway end zone corresponding to the second behavior and a third runway end zone corresponding to the third behavior.;

4. Method according to one of the preceding claims, in which it comprises: - A continuous recording of the angular aperture of the primary camera, - For a given image at a given time t: • taking the average of x previous images tempo- so the given image and get an averaged image, • Subtract the given image from the averaged image.

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

6. 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.

7. 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.

8. Method according to the preceding claim, 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 approach end region.

9. Method according to the preceding claim, in which the first low line has an inclination of a non-zero angle α relative to the axis of said at least one track.

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

11. 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.

12. Method according to the preceding claim, in which the op-tronic 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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