Method for three-dimensional localization of an aircraft within a landing scene comprising at least one landing runway

Abstract

Method for three-dimensional localization of an aircraft within a landing scene comprising at least one landing runway The invention relates to a method (40) for localizing an aircraft within a scene comprising at least the following steps: - in a radar reference frame, obtaining (42) at least: - the distance to the radar and the circular of a point of the scene, - the distance to the ground in the radar sighting axis; - determining (44) a matrix of change of reference frame of said radar reference frame to a local geographical reference frame using the attitude of the aircraft; - determining (46), in the radar reference frame, the elevation of said point corresponding to the arc sine of the solution of an equation obtained by determining the component of said predetermined point along the altitude axis of said local geographical reference frame, both from said distance to the ground, the attitude, and the application of said matrix to the coordinates of said point. Figure for abstract: Figure 2

Description

Title of the invention: Method for three-dimensional localization of an aircraft within a landing scene comprising at least one landing runway

[0001] The present invention relates to a method for three-dimensional localization of an aircraft within a landing scene comprising at least one landing runway, said aircraft carrying at least one radar, the landing scene being considered substantially planar in the domain of the angular aperture of said radar.

[0002] The invention also relates to a computer program comprising software instructions which, when implemented by a programmable electronic device, implement such a method.

[0003] The invention also relates to an electronic device for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway, said aircraft carrying at least one radar, the landing scene being considered substantially planar in the domain of the angular aperture of said radar.

[0004] The invention also relates to a landing assistance system comprising at least one radar and such a device.

[0005] The invention also relates to an aircraft comprising such a landing assistance system.

[0006] The invention lies in the field of aircraft navigation. In this field in particular, it is known to equip aircraft with landing aid devices capable in particular of determining the position of the aircraft relative to the landing runway.

[0007] In particular, to land in conditions of reduced visibility, in particular in the presence of fog, snow, heavy rain, etc., the crew or pilot of an aircraft generally relies on on-board equipment corresponding to such landing aid devices including, in a known manner, instrument landing systems ILS (from the English Instrument Landing System), microwave landing systems MLS (from the English Microwave Landing System), a GPS receiver making it possible in particular to obtain a geolocated position of the aircraft, etc. and also relies on ground landing aid infrastructures such as approach light ramps, an approach slope indicator PAPI (from the English Precision Approach Path Indicator), the beacons used by the instrument landing system ILS such as the runway axis, the plane descent slope leading to the runway, the runway threshold, the runway itself, the touchdown zone, etc.

[0008] However, when the visibility and / or radio navigation conditions are insufficient, such conventional solutions are limited because they do not offer sufficient precision to comply with the air navigation safety objectives applied to the different types of approach and landing, or require one or more specific infrastructures that are costly or impossible to implement regardless of the landing zone.

[0009] To remedy this, it is generally proposed to determine the angular deviations of the aircraft relative to its ideal final approach trajectory FAS (Final Approach Segment), in particular from radar measurements.

[0010] However, due to the geometry of its radar antenna(s), each radar antenna having a width substantially six times greater than its height, the determination of the elevation of a predetermined point of the landing scene in the predetermined radar reference frame associated with the radar, in particular a point of interest, is doomed to failure in terms of accuracy, said elevation corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference frame to said predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, the circular of said predetermined point corresponding to the angle formed from the line of sight of the radar up to the projection of said predetermined point of said landing scene in the projection plane of the circulars, this plane being defined by the line of sight of the radar, and the axis of the angular measurements of said radar reference frame.

[0011] The aim of the invention is then to propose a solution providing, to the conventional solutions for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway, additional precision which is consistent with the safety objectives of air navigation applied to the different types of approach and landing.

[0012] To this end, the invention relates to a method for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway, said aircraft carrying at least one radar, the landing scene being considered substantially planar in the domain of the angular aperture of said radar, said method comprising at least the following successive steps:

[0013] - in a predetermined radar reference associated with said radar, the origin of which corresponds to the phase center of the antenna of said at least one radar, obtaining at least:

[0014] - the distance to the radar and the circular of at least one predetermined point of the scene landing, obtained from measurements of said radar, the circularity of said at least one predetermined point corresponding to the angle formed from the line of sight of the radar to the projection of said at least one predetermined point of said scene landing in the projection plane of the circulars, this plane being defined by the radar sighting axis, and the axis of the angular measurements of said radar reference mark, and

[0015] - the distance to the ground in the radar line of sight, from the phase center of the antenna of said at least one radar;

[0016] - determination of a reference change matrix allowing passage from said predetermined radar reference to a predetermined local geographical reference whose origin corresponds to the phase center of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll, pitch and yaw angles defining the attitude of the aircraft, these angles being provided beforehand by an inertial unit of the aircraft;

[0017] - determination, in the radar reference frame, of the elevation of said at least one pre-point determined from said landing scene, said elevation corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference mark to said at least one predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, said elevation corresponding to the arc sine of the solution of a second degree equation obtained by determining the component of said at least one predetermined point of said landing scene along the axis of altitudes of said local geographical reference mark, both from said distance to the ground in the radar line of sight and from said pitch angle, and from the application of said reference mark change matrix to the coordinates of said at least one predetermined point of the landing scene measured and expressed in said radar reference mark;

[0018] - determination, in said radar reference frame, of the three-dimensional location of said at at least one predetermined point of said landing scene, from said radar distance, said circular and said elevation of said at least one predetermined point of said landing scene.

[0019] Thus, the present invention proposes to determine with precision, in the radar reference frame, the elevation of at least one predetermined point of the landing scene to improve the precision of the subsequent location of the aircraft as such.

[0020] More specifically, the present invention proposes to take advantage of the fact that the height of the radar relative to the circular projection plane is unique and this for any predetermined point in the line of sight of the radar, under the assumption of a flat landing scene in the domain of the angular aperture of said radar. Thus, knowing on the one hand the pitch of the aircraft and the distance to the ground in the line of sight which is insensitive to rolling, and on the other hand the application of said reference frame change matrix to the coordinates of said predetermined point of the landing scene measured and expressed in said radar reference frame, it is possible to precisely determine said previously unknown elevation.

[0021] According to other advantageous aspects of the invention, the three-way localization method dimensional of an aircraft within a landing scene comprising at least one landing runway comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0022] - the method further comprises the following steps:

[0023] - determination of the three-dimensional location of said at least one pre-point determined from said landing scene expressed in said local geographic reference frame by applying said reference frame change matrix to said three-dimensional location of said at least one predetermined point of said landing scene in said radar reference frame;

[0024] - from the three-dimensional location expressed in the geographic reference point local, obtaining the three-dimensional location of said radar expressed in a predetermined reference frame of the landing runway whose origin is a predetermined point of said landing runway and whose two axes correspond respectively to the longitudinal axis and the transverse axis of the runway, said obtaining comprising the inversion of the sign of the component along the altitude axis of said at least one predetermined point of the landing scene expressed in said local geographical reference frame;

[0025] - determining the vertical angular deviation of said aircraft relative to a reference approach path, using the three-dimensional location of said radar translated along the x-axis from the runway reference mark to the GPIP point of intersection of the reference approach path with the landing runway;

[0026] - determining the lateral angular deviation of said aircraft relative to the tra reference approach target, using the three-dimensional location of said radar, translated along the x-axis from the runway reference to the GARP reference point for determining lateral deviations;

[0027] - said at least one predetermined point of said landing scene corresponds to the middle S of the threshold of said landing runway;

[0028] - said at least one predetermined point of said landing scene corresponds to a point of intersection A of two lines of approach lights perpendicular to each other, and in which the norm of the vector going from said point of intersection A to the middle S of the threshold of said landing runway is also taken into account (58), when determining (56) the vertical angular deviation and the lateral angular deviation, by translating, from said norm, the position of said radar, expressed in the predetermined reference of said runway along the x axis;

[0029] - said determination of a reference change matrix comprises three successive changes of reference, namely:

[0030] - a first change of reference from the radar reference to the reference of the aircraft used by said inertial unit to provide the roll, pitch and yaw angles defining the attitude of the aircraft, using the inclination of said radar; then

[0031] - a second change of reference from the aircraft reference to a geo reference intermediate graph showing: an origin corresponding to the phase center of the antenna of said radar, an abscissa axis according to the terrestrial geographic North direction, an ordinate axis according to the terrestrial geographic East direction and an altitude axis according to the terrestrial geographic local vertical;

[0032] - a third change of reference from the intermediate geographical reference to said predetermined local geographic reference point defined relative to the landing scene plan.

[0033] - the method further comprises, prior to obtaining the three-dimensional localization dimension of said radar expressed in a predetermined reference frame of the landing runway, the application of a rotation around the altitude axis of the local geographical reference frame according to a predetermined angle representative of the error in determining the yaw angle W by said inertial unit of the aircraft, said predetermined angle representative of the error in determining the yaw angle being obtained, prior to the application of said rotation, from a point Q defined by its spherical coordinates in the radar reference frame, such that:

[0034] - its distance from the phase center of the antenna of said radar is unitary,

[0035] - its circularity is equal to the orientation of the longitudinal axis of said track landing expressed in the radar reference and previously obtained from said measurements of said radar;

[0036] - its elevation angle is zero,

[0037] the point Q then being expressed in Cartesian coordinates in said local geographical reference frame by means of said reference frame change matrix, said predetermined angle ew representative of the error in determining the yaw angle being such that sv- atan2^yQ, xG]-

[0038] The invention also relates to a computer program comprising software instructions which, when executed by a computer, implement a method for three-dimensional localization of an aircraft within a landing scene comprising at least one landing runway, as defined above.

[0039] The invention also relates to an electronic device for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway, said aircraft carrying at least one radar, the landing scene being considered substantially planar in the domain of the angular aperture of said radar, said device comprising:

[0040] - a first module configured to implement, in a pre-set radar reference determined associated with said radar, the origin of which corresponds to the phase center of the antenna of said at least one radar, obtaining at least:

[0041] - the distance to the radar and the circular of at least one predetermined point of the scene landing, obtained from measurements of said radar, the circular of said predetermined point of said landing scene corresponding to the angle formed from the line of sight of the radar to the projection of said at least one predetermined point in the plane of projection of the circulars, this plane being defined by the line of sight of the radar and the axis of the angular measurements of said radar reference mark, and

[0042] - the distance to the ground, in the radar line of sight, from the phase center of the antenna of said at least one radar;

[0043] - a second module configured to determine a change matrix of reference point enabling the transition from said predetermined radar reference point to a predetermined local geographical reference point whose origin corresponds to the phase centre of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll, pitch and yaw angles defining the attitude of the aircraft, these angles being provided beforehand by an inertial unit of the aircraft;

[0044] - a third module configured to determine, in the radar reference frame, the elevation of said at least one predetermined point of said landing scene, said elevation corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference mark to said at least one predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, said elevation corresponding to the arc sine of the solution of a second degree equation obtained by determining the component of said at least one predetermined point of said landing scene along the axis of altitudes of said local geographical reference mark, both from said distance to the ground in the radar line of sight and from said pitch angle, and from the application of said reference mark change matrix to the coordinates of said at least one predetermined point of the landing scene measured and expressed in said radar reference mark;

[0045] - a fourth module configured to determine, in said radar reference frame, the loca three-dimensional lization of said at least one predetermined point of said landing scene, from said radar distance, said circular and said elevation of said at least one predetermined point of said landing scene

[0046] The invention also relates to a landing assistance system comprising at least one radar and such an electronic device for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway.

[0047] The invention also relates to an aircraft comprising such a landing assistance system.

[0048] The invention will appear more clearly on reading the description which follows, given solely as a non-limiting example, and made with reference to the drawings in which:

[0049] [Fig.l] [Fig.l] is a block diagram of the main functional blocks of an electronic device for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway;

[0050] [Fig.2] [Fig.2] is a flowchart of the main steps of a loca process three-dimensional rendering of an aircraft within a landing scene comprising at least one landing strip;

[0051] [Fig.3] [Fig.3] illustrates the successive changes of reference implemented according to the present invention.

[0052] In the remainder of the description, the expression “substantially equal to” is understood as a relationship of equality to plus or minus 10%, that is to say with a variation of at most 10%, more preferably as a relationship of equality to plus or minus 5%, that is to say with a variation of at most 5%.

[0053] [Fig.l] illustrates an embodiment of an electronic device 10 for three-dimensional location of an aircraft within a landing scene comprising at least one landing strip according to an embodiment of the invention.

[0054] Such a device is suitable for being integrated within a landing assistance system, not shown, comprising at least one radar, in particular millimetric radar, not shown, said landing system itself being suitable for being carried on board an aircraft, not shown.

[0055] More precisely, the electronic three-dimensional location device 10, according to the present invention, is capable of implementing the method for three-dimensional location of an aircraft within a landing scene comprising at least one landing strip which will be described subsequently in relation to [Fig.2].

[0056] To do this, such a device 10 firstly comprises a first obtaining module 12 configured to obtain, in a predetermined radar reference associated with said radar as illustrated below in relation to [Fig.3], the origin of which corresponds to the phase center of the antenna of said at least one radar, at least:

[0057] - the distance p to the radar and the circular a of at least one predetermined point of the landing scene, obtained from measurements of said radar, the circular of said predetermined point corresponding to the angle formed from the line of sight of the radar to the projection of said predetermined point of said landing scene in the plane of projection of the circulars, this plane being defined by the line of sight of the radar, and the axis of the angular measurements of said radar reference mark, and

[0058] - the ground distance D in the radar line of sight, from the phase center of the antenna of said at least one radar.

[0059] In addition, the device 10 comprises a first configured determination module 14 to determine a reference change matrix making it possible to pass, as illustrated below in relation to [Fig. 3], from said predetermined radar reference to a predetermined local geographical reference whose origin corresponds to the phase center of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll, pitch and yaw angles defining the attitude of the aircraft, these angles being provided beforehand by an inertial unit of the aircraft.

[0060] Then, the device 10 comprises a second determination module 16, configured to determine in the radar reference frame, the elevation [3 of said predetermined point of said landing scene, said elevation corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference frame to said predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, said elevation [3 corresponding to the arc sine of the solution of a second degree equation obtained by determining the component of said predetermined point of said landing scene along the axis of altitudes of said local geographical reference frame, both from said distance to the ground in the radar line of sight and from said pitch angle, and from the application of said reference frame change matrix to the coordinates of said predetermined point of the landing scene measured and expressed in said radar reference frame.

[0061] The device 10 also comprises a third module 18 for determining, in said radar reference frame, the three-dimensional location of said at least one predetermined point of said landing scene, from said radar distance, from said circular and from said elevation of said predetermined point of said landing scene.

[0062] As an optional addition, as shown in dotted lines, said electronic three-dimensional location device 10, according to the present invention, further comprises a fourth determination module 20 configured to determine the three-dimensional location of said at least one predetermined point of said landing scene expressed in said local geographic reference frame by applying said reference frame change matrix to said three-dimensional location of said at least one predetermined point of said landing scene in said radar reference frame.

[0063] According to this optional addition, said device 10 also comprises a second obtaining module 22 configured to obtain, from the three-dimensional location expressed in the local geographical reference frame, the three-dimensional location of said radar expressed in a predetermined reference frame of the landing runway whose origin is a predetermined point of said landing runway and whose two axes correspond respectively to the longitudinal axis and to the transverse axis of the runway, said obtaining comprising the inversion of the sign of the component along the axis of the altitudes of said predetermined point of the landing scene expressed in said geographical reference frame. local graph.

[0064] Furthermore, according to this optional addition, said device 10 also comprises a fifth determination module 24, configured to determine the vertical angular deviation of said aircraft relative to a reference approach trajectory, using the three-dimensional location of said radar translated along the x-axis from the runway reference to the GPIP point of intersection of the reference approach trajectory with the landing runway (from the English Glide Path Intercept Point).

[0065] Finally, according to this optional addition, said device 10 also comprises a sixth determination module 26, configured to determine the lateral angular deviation of said aircraft relative to the reference approach trajectory, using the three-dimensional location of said radar, translated along the x-axis from the runway reference to the GARP reference point for determining lateral deviations (GNSS Azimuth Reference point).

[0066] The GARP and GPIP points are the references of the lateral and vertical deviations respectively as defined in document DO-229E in paragraphs 2.2.4.3.1 and 2.2.4.4.2.3 of the Radio Technical Commission for Aeronautics (RTCA).

[0067] According to another optional addition, said device 10 further comprises an application module 28 configured to apply, prior to obtaining the three-dimensional location of said radar expressed in a predetermined reference frame of the landing runway, a rotation around the altitude axis of the local geographical reference frame according to a predetermined angle ew representative of the error in determining the yaw angle V by said inertial unit of the aircraft, said predetermined angle representative of the error in determining the yaw angle being obtained, prior to applying said rotation, from a point Q defined by its spherical coordinates in the radar reference frame, such that:

[0068] - its distance from the phase center of the antenna of said radar is unitary,

[0069] - its circularity is equal to the orientation of the longitudinal axis of said track landing expressed in the radar reference and previously obtained from said measurements of said radar;

[0070] - its elevation angle is zero,

[0071] the point Q then being expressed in Cartesian coordinates in said local geographical reference frame by means of said reference frame change matrix, said predetermined angle sw representative of the error in determining the yaw angle being such that Exp — atan2 ( y Xo j ■

[0072] In the example of [Fig.l], electronic device 10 for three-dimensional localization of an aircraft within a landing scene comprises a unit of processing 30 formed for example of a memory 32 and a processor 34 associated with the memory, and the device 10 is at least partly produced in the form of software, or a software brick, executable by the processor, in particular the first obtaining module 12, the first determining module 14, the second determining module 16, the third determining module 18, and optionally the fourth determining module 20, the second obtaining module 22, the fifth determining module 24, the sixth determining module 26 and the application module 28. The memory 32 of the electronic device 10 for three-dimensional location of an aircraft within a landing scene is then capable of storing such software or software bricks, and the processor 34 is then capable of executing them.

[0073] In a variant not shown, the first obtaining module 12, the first determining module 14, the second determining module 16, the third determining module 18, and optionally the fourth determining module 20, the second obtaining module 22, the fifth determining module 24, the sixth determining module 26 and the application module 28 are each produced in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array) or in the form of a dedicated integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0074] When a part of the electronic device 10 for three-dimensional location of an aircraft within a landing scene according to the present invention is produced in the form of one or more software programs, that is to say in the form of a computer program, this part is furthermore capable of being recorded on a medium, not shown, readable by a computer. The computer-readable medium is, for example, a medium capable of storing electronic instructions and of being coupled to a bus of a computer system. By way of example, the readable medium is an optical disk, a magneto-optical disk, a ROM memory, a RAM memory, any type of non-volatile memory (for example EPROM, EEPROM, FLASH, NVRAM), a magnetic card or even an optical card. A computer program comprising software instructions is then stored on the readable medium.

[0075] An example of operation of the electronic device 10 for three-dimensional location of an aircraft within a landing scene according to the present invention is described below in relation to [Fig. 2] as illustrated previously in relation to [Fig. 1].

[0076] More precisely, the method 40 for three-dimensional localization of an aircraft within a landing scene generally comprises a first step 42 of obtaining OBT(p, a, D) of at least, on the one hand the distance to the radar, noted p, and the circular noted a of at least one predetermined point of the landing scene, obtained from measurements of said radar, the circular a of said predetermined point corresponding at the angle formed from the line of sight of the radar to the projection of said predetermined point of said landing scene in the projection plane of the circulars, this plane being defined by the line of sight of the radar, and the axis of the angular measurements of said radar reference mark, and on the other hand of the distance to the ground D in the line of sight of the radar, from the phase center of the antenna of said at least one radar.

[0077] The elements p, a, D are obtained in the predetermined radar reference frame associated with said radar, the origin of which corresponds to the phase center of the antenna of said at least one radar as illustrated below in relation to [Fig.3].

[0078] Furthermore, such elements can be obtained according to different variants.

[0079] For example, according to a first variant, the elements are capable of being obtained at least in part by using a solution based on artificial intelligence learning using a deep learning tool based in particular on attention mechanisms applied in a non-trivial manner specifically to radar measurements as described in the patent application whose filing number is FR2309055 in the name of the Applicant.

[0080] According to another variant, these elements are capable of being obtained at least in part using the solution described in patent FR 3 103 178 in the name of the Applicant.

[0081] The method 40 for three-dimensional localization of an aircraft within a landing scene then generally comprises a step 44 of determining DET_M a matrix M of change of reference frame making it possible, as illustrated below in relation to [Fig. 3], to pass from said predetermined radar reference frame to a predetermined local geographical reference frame whose origin corresponds to the phase center of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll, pitch and yaw angles defining the attitude of the aircraft, these angles being provided beforehand by an inertial unit of the aircraft.

[0082] The method 40 for three-dimensional localization of an aircraft within a landing scene then generally comprises a step 46 of determining DET_ [3, in the radar reference frame, the elevation [3 of said predetermined point of said landing scene, said elevation corresponding, as explained below in relation to [Fig. 3], to the opposite of the angle formed from the vector starting from the origin of the radar reference frame to said predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, said elevation corresponding to the arc sine of the solution of a second-degree equation obtained by determining the component of said predetermined point of said landing scene along the altitude axis of said local geographical reference frame, both from said distance to the ground in the radar line of sight and from said pitch angle, and from the application from said reference frame change matrix to the coordinates of said predetermined point of the landing scene measured and expressed in said radar reference frame.

[0083] The method 40 for three-dimensional localization of an aircraft within a landing scene then generally comprises a step 48 of determining DET_LOCr in said radar reference frame, the three-dimensional localization of said at least one predetermined point of said landing scene, from said radar distance p, said circular a and said elevation [3 of said predetermined point of said landing scene.

[0084] As an optional addition, the method 40 for three-dimensional localization of an aircraft within a landing scene also comprises a step 50 of determining DET_LOCg the three-dimensional localization of said at least one predetermined point of said landing scene expressed in said local geographical reference frame by applying said matrix M of change of reference frame to said three-dimensional localization of said at least one predetermined point of said landing scene in said radar reference frame.

[0085] Optionally, as shown in dotted lines, the method 40 for three-dimensional localization of an aircraft within a landing scene also comprises a step 52 of applying a rotation ROT around the altitude axis of the local geographical reference frame according to a predetermined angle representative of the error in determining the yaw angle by said inertial unit of the aircraft, said predetermined angle representative of the error in determining the yaw angle being obtained, prior to the application of said rotation, from a point Q defined by its spherical coordinates in the radar reference frame, such that:

[0086] - its distance from the phase center of the antenna of said radar is unitary,

[0087] - its circularity is equal to the orientation of the longitudinal axis of said track landing expressed in the radar reference and previously obtained from said measurements of said radar;

[0088] - its elevation angle is zero,

[0089] the point Q then being expressed in Cartesian coordinates in said local geographical reference frame by means of said reference frame change matrix, said predetermined angle s'i; representative of the error in determining the yaw angle being such that en, = atan2 yo, Xq j •

[0090] As an optional addition, the method 40 for three-dimensional localization of an aircraft within a landing scene also comprises, from said three-dimensional localization expressed in the local geographical reference, a step 54 of obtaining OBT_LOC(R)P the three-dimensional localization of said radar R expressed in a predetermined reference of the landing runway whose origin is a predetermined point of said landing runway and two axes of which correspond respectively to the longitudinal axis and the transverse axis of the runway, said obtaining comprising the inversion of the sign of the component along the axis of the altitudes of said predetermined point of the landing scene expressed in said local geographical reference, the index P being here representative of the fact that the location is in the reference of the runway.

[0091] As an optional addition, the method 40 for three-dimensional localization of an aircraft within a landing scene also comprises a step 56 determining DET_DEVv the vertical angular deviation of said aircraft relative to a reference approach trajectory, using the three-dimensional localization of said radar translated along the x-axis from the runway reference frame to the GPIP point of intersection of the reference approach trajectory with the landing runway.

[0092] Optionally, as illustrated in Figure 2 in dotted lines, said at least one predetermined point of said landing scene corresponds to a point of intersection A of two lines of approach lights perpendicular to each other, the norm of the vector AS going from said point of intersection A to the middle S of the threshold of said landing runway is then also taken into account according to the optional sub-step 58, during the determination 56 of the vertical angular deviation, by translating, from said norm, the position of said radar, expressed in the predetermined reference frame of said runway along the x axis.

[0093] Finally, as an optional addition as illustrated by [Fig.2], the method 40 for three-dimensional localization of an aircraft within a landing scene also comprises a step 60 of determining DET_DEVL the lateral angular deviation of said aircraft relative to the reference approach trajectory, using the three-dimensional localization of said radar, translated along the x-axis from the runway reference to the reference GARP point for determining the lateral deviations.

[0094] It should be noted that in a manner not shown, when said at least one predetermined point of said landing scene corresponds to a point of intersection A of two lines of approach lights perpendicular to each other, the norm of the vector as going from said point of intersection A to the middle S of the threshold of said landing runway is then also taken into account according to the optional sub-step 58 during the determination 60 of the lateral angular deviation, by translating, from said norm, the position of said radar, expressed in the predetermined reference frame of said runway along the x axis.

[0095] An example of implementation of the steps of the method 40 previously cited is described below in detail in relation to [Fig.3] illustrating the successive changes of reference implemented according to the present invention.

[0096] More precisely, according to the example illustrated by [Fig.3], a predetermined radar reference mark 62 is used whose origin O corresponds to the phase center of the radar antenna. In addition, the x axis of the abscissas of the predetermined radar reference mark 62 is along the axis of aiming of the radar, while the y axis of the ordinates in the plane 64 of projection of the circulars is perpendicular to this x axis of aiming, and parallel to the line of the transmitters (i.e. to the width of the radar), and in particular oriented towards the right when looking along the aiming of the radar. The z axis of the altitudes is according to this example such that the radar reference mark 62 is direct orthonormal (i.e.

[0097] downwards if the aircraft attitude is zero).

[0098] As indicated previously, the first step 42 of the method 40 according to the present invention consists in obtaining on the one hand the distance to the radar, in particular in meters, noted p in [Fig. 3], and the circular noted a, in particular in radians, of at least one predetermined point P of the landing scene, obtained from measurements of said radar, the circular a of said predetermined point corresponding to the angle formed from the radar sighting axis x to the projection of said predetermined point of said landing scene in the plane 64 of projection of the circulars, this plane 64 being defined by the radar sighting axis x, and the axis of the angular measurements of said radar reference frame, and on the other hand the distance to the ground D in the radar sighting axis, in particular in meters, from the phase center of the antenna of said at least one radar, and corresponding to the distance of said center to the point Po of intersection (not shown) with the ground.

[0099] In particular, in the example of [Fig.3], the circular noted a is thus defined in the radar reference frame 62 and corresponds to the angle formed from the origin O and the line of sight x of the radar, in the plane 64 (O, x, y) and oriented positively following the rotation around (O, z).

[0100] As indicated previously, different variants are suitable for use for the implementation of said obtaining step such as a solution based on learning by artificial intelligence using a deep learning tool based in particular on attention mechanisms applied in a non-trivial manner specifically to radar measurements such as described in the patent application whose filing number is FR2309055 in the name of the Applicant or the solution described in patent FR 3 103 178 in the name of the Applicant.

[0101] In particular, said at least one predetermined point corresponds to a plurality of points P; identifying in particular the threshold and the edges of the runway, or the axes of the approach lights.

[0102] Another variant of obtaining 42, consists of identifying the contour of the runway by detection or segmentation applied to the “radar grid”, the straight line segments of this contour are then located by Hough transform or affine adjustment, and a verification is carried out so as to ensure that the segments of the edges and the threshold of the runway thus identified are such that: the edges of the runway are substantially parallel (in particular with an orientation error of less than 1°, the threshold of the runway is perpendicular to the edges (in particular with an orientation error of less than 2°), and that the runway is a rectangle with likely dimensions (for example, the runway edges are spaced less than 18m apart and more than 300m long). According to this variant, the intersection of the median of the runway edges with the runway threshold is the point S corresponding to the midpoint S of the threshold of said landing runway, and the orientation V of the runway, expressed in the radar reference frame, is derived from the direction coefficient a, expressed in the radar reference frame, of the median line of the runway edges such that y = ataiïl(a, 1)

[0103] Thus, as illustrated by [Fig.3], in such a radar reference frame 62, P is considered to be one of these points Pi, defined by its distance from the radar p and its angles a and [3 such that: a being the circular of P as defined previously and [3 the elevation of said predetermined point corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference frame to said predetermined point P of said landing scene in the plane 66 (O, P, z), up to the projection of this vector in the plane 64 of projection of the circulars.

[0104] The Cartesian coordinates of P in such a radar reference frame 62, also called reference frame R, are then such that: = p ■ cos ( a ) • cos ( fi ), y[Æ] = p ■ sin( a ) ■ cos( / ?) et = p ■ sin(^)

[0105] However, as previously indicated, determining the elevation [3 of a predetermined point of the landing scene, in particular a point of interest, is doomed to failure in accuracy, it is therefore considered unknown at this stage of the method and as represented by means of a question mark in [Fig.3].

[0106] As indicated previously, the second step 44 of the method consists, in parallel or not with the obtaining step 42 previously described, in determining a reference frame change matrix making it possible to pass from said predetermined radar reference frame 62, also called reference frame R, to a predetermined local geographical reference frame G' whose origin corresponds to the phase center of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll, pitch and yaw angles defining the attitude of the aircraft, these angles being supplied beforehand by an inertial unit of the aircraft.

[0107] More precisely, said determination 44 of a reference frame change matrix comprises three successive reference frame changes, namely a first reference frame change 68 from the radar reference frame 62 to the reference frame 70 of the aircraft, also subsequently called reference frame B, used by said inertial unit to provide the angles of:

[0108] - roll q> around the roll axis 72 corresponding to the longitudinal axis of the aircraft, and therefore in the presence of pitching most of the time non-zero, positive if leaning towards the right,

[0109] - pitch 0 around the pitch axis 74, in particular defined with respect to the ho- plane terrestrial and positive rhizomatous in rearing, and

[0110] - yaw rp around the yaw axis 76, in particular defined relative to geo north land graph, and positive towards the East.

[0111] defining the attitude of the aircraft to within plus or minus 0.05°, using the inclination i of said radar defined relative to the plane of faith of the aircraft and in particular positive if the radar points downwards.

[0112] The reference change matrix used during this first reference change is subsequently called R2B.

[0113] In addition, said determination 44 of a reference frame change matrix comprises a second change of reference frame from the reference frame 70 of the aircraft to an intermediate geographical reference frame G not shown having: an origin corresponding to the phase centre of the antenna of said radar, an abscissa axis x along the terrestrial geographic North direction, an ordinate axis y along the terrestrial geographic East direction and an altitude axis z along the terrestrial geographic local vertical.

[0114] The reference frame change matrix, called B2G, used during this second change of reference frame from the aircraft reference frame 70 to an intermediate geographical reference frame G is such that it is the transposed matrix of the G2B matrix allowing the passage from the intermediate geographical reference frame to the aircraft reference frame 70, such that:

[0115] / cos(v')-cos(0) sin(y>)-cos(0) -sin(^) \ G2B = cos(v)-sin(S)-sin]^)-sin(y>)-cos(p) sin(y>) -sinf 6*)-sin(p) +cos(y')-cos(^) cos(0)-sin(^) \cos(y>) ■ sin( 0) ■ cos(p) +sin( y.') • sin(<p) sin( y;) ■ sin(^) ■ cos(y> ) -cos( >p) ■ sin(^) cos(0) ■ cos( <p) /

[0116] où G2B(n, p) désigne le terme en ligne n et colonne P, l’ordre des rotations dans ce deuxième changement de repère G2B ; cap (^), puis tangage (0), puis roulis (9).

[0117] The order of rotations is advantageous. As previously indicated, the distance to the ground in the line of sight is insensitive to roll and because in the order of rotations defining the attitude of the aircraft, the roll is applied after the pitch, it is possible to determine the height of the radar relative to the ground independently of the roll.

[0118] In other words, p2G — (G?#)^' and the matrix R2B associated with the first change of reference is defined as G2B but considering that 0 = i and ip — (p — 0, i being the inclination of said radar defined in relation to the plane of faith of the aircraft and in particular positive if the radar points downwards.

[0119] It should be noted that taking into account the definition of the vertical and lateral angular deviations commonly retained by ILS instrument landing systems (from the English Instrument Landing System) and radar measurements, said determination 44 of a reference frame change matrix comprises a third reference frame change from the intermediate geographical reference frame not shown to said predetermined local geographical reference frame, noted G', defined relative to the plane of the landing scene, using a reference frame change matrix G2G' associated with this third change of reference.

[0120] In other words, arrow 78 of [Fig.3] is equivalent to direct application of the second and then the third change of reference point mentioned above to move directly from the reference point 70 of the aircraft to said predetermined local geographical reference point.

[0121] This predetermined local geographical reference point is defined relative to the inclination i of the radar and to the plane of the approach scene (i.e. landing scene) considered, according to the present invention, substantially flat in the domain of the angular opening of said radar.

[0122] In particular, the axes of this predetermined local geographical reference point are merged with those of the aforementioned intermediate geographical reference point not shown when the longitudinal slopes Si and transverse slopes st of the approach scene, which are known (such as entrances), as well as the geographical orientation of the runway also known according to the direction of landing, in particular defined with respect to the terrestrial geographic North and positive towards the East, are all three zero. The longitudinal slope Si of the approach scene is in particular defined with respect to the terrestrial horizontal plane and positive if the scene is rising while the transverse slope st, zero in principle, is defined with respect to the terrestrial horizontal plane and positive if the scene leans towards the right when looking along the axis of the runway in the direction of landing.

[0123] Note that for reasons of cost constraints, the aircraft and runway headings are generally only approximately known, i.e. to within a few degrees.

[0124] The abscissa axis x of the predetermined local geographical reference point is oriented along the axis of the runway, in the direction of landing and at the level of the TDZ (Touch Down Zone), with correction using the known input parameters corresponding to the geographical orientation of the runway and to the longitudinal slope Si of the approach scene.

[0125] The y-axis of the predetermined local geographical reference is oriented along the transverse axis of the track at the level of the contact zone TDZ, with correction using the same parameters rppiste and st.

[0126] The altitude axis z of the predetermined local geographic reference point is notably oriented such that (O, x, y, z) is directly orthonormal.

[0127] The origin of this reference frame remains the phase center of the radar antenna O as illustrated in radar reference frame 62.

[0128] The reference frame change matrix G2G' associated with this third reference frame change is such that G2G' is then defined as G2B but with = and and tp — st.

[0129] According to [Fig.3], the predetermined local geographic reference as described above is represented by the reference point 80 after translation of said predetermined local geographical reference point, the origin of which remains the phase center of the radar antenna O, in the middle S of the threshold of runway 82. Note that the angular error of the axes of this local geographical reference point 80 due to the distance SO (< 1 NM) remains negligible (2 / 100° to 2 km) with regard to the required performances (from 2 to 4 / 10°) taking into account the Earth radius (approximately 6400 km).

[0130] By hypothesis of the approach scene, the plurality of points P; identifying in particular the threshold and the edges of the runway, or the axes of the approach lights are all located in the same plane, and by definition predetermined local geographical reference as described above, the “height” h of the radar relative to the plane of the approach scene (i.e. its coordinate along the z axis of the predetermined local geographical reference G' is then such q^ / ^l^pD-sin^

[0131] The matrix M allowing to pass from said predetermined radar reference to a predetermined local geographical reference is such that M = G2G ■ B2G ■ R2B = R^G'

[0132] In the equation defining the Cartesian coordinates 'M ^gq of said at least one predetermined point of said landing scene expressed in said predetermined local geographical reference frame G' as a function of said matrix M and the coordinates 3'[Aj of said at least one predetermined point of said landing scene expressed in the radar reference frame R, the only unknowns are / i and consequently 3¼ V'I because = p ■ cos ( a ) • COS ( fi ), y , = p ■ sin ( a ) • cos ( fi ) and^p-sin^)-

[0133] Applying the reference change equation to the z component then makes it possible to determine [3 from ,, 7 \ because the height z of the radar relative to the plane vVI -VT m] / (O, x, y) of the predetermined local geographic reference G' is unique, and this for any point P under the assumption of a flat scene. So that an equation in the following form is obtained:

[0134] ^ = 0-811)(0+1 + .¾) =R2G (3,1) -p-cos(a) -cos(^) + R2G (3,2) ' / rsin / fz) -cos(^) + Æ2G (3,3) ■

[0135] This equation is of the form: A ■ cos( / 7) + B ■ sin( / 3) = C by setting:

[0136] A — p-R2G(3,l) -cos(a) + p-R2G(3,2) -sin(a)

[0137] B = p-R2G (3,3)

[0138] C = D-sin(0)

[0139] Considering: cos2 ( fi ) = 1 - sure ( fi ) and setting: X = sin ( fi ) the equation becomes, the root term being isolated and the equation squared:

[0140] (A2 + b2).X2 2. (BC) -X+(C2-A2) =0

[0141] The roots of this second degree equation are as follows, according to a for- emulation with reduced discriminant:

[0142] (bc) (bc)2- (a2+b2 i) X: — ------------5 ----------- ' A2+B2

[0143] noting that there is no solution to retain for this equation if the reduced discriminant is strictly negative, or if two solutions are negative, said at least one predetermined point being assumed to be under the plane of faith of the aircraft.

[0144] The determination of the solution Xj then makes it possible, as indicated previously, to determine 46 the elevation [3 of said predetermined point of which it is the arc sine, and consequently to determine 48 the Cartesian coordinates ^[«1 of said at minus a predetermined point expressed in the radar reference with:

[0145] x[Æ] = p-cos(a) ■cos(^),y[ / î] = p-sin(a) -cosO) and ^M = p- sin(^)-

[0146] Once this determination 48 of the Cartesian coordinates ■'W ZLR] of said at least one predetermined point expressed in the radar reference frame has been carried out, it is then possible to determine 50 the Cartesian coordinates 9g'| of said at least one less than one predetermined point expressed in the predetermined local geographic reference frame G' by application of the reference frame change matrix R2G'.

[0147] As an optional addition, said at least one predetermined point of said landing scene corresponds to the threshold midpoint S of said landing runway.

[0148] As indicated previously, as an alternative to the optional addition above, said at least one predetermined point of said landing scene corresponds to a point of intersection A of two lines of approach lights perpendicular to each other, and in which the norm of the vector going from said point of intersection A to the middle S of the threshold of said landing runway is also taken into account 58, during the determination 56 of the vertical angular deviation and the lateral angular deviation, by translating, from said norm, the position of said radar, expressed in the predetermined reference frame of said runway along the abscissa axis x.

[0149] As indicated in Figure 2, prior to obtaining 54 the three-dimensional location of said radar expressed in a predetermined reference frame of the landing runway as illustrated in Figure 3 by the predetermined reference frame 86, the method comprises an optional step 52 of applying a rotation ROT around the altitude axis of the local geographical reference frame according to a predetermined angle £w representative of the error in determining the yaw angle W by said inertial unit of the aircraft, said predetermined angle representative of the error in determining the yaw angle being obtained, prior to applying said rotation, from a point Q defined by its spherical coordinates in the radar reference frame, such that:

[0150] - its distance from the phase center of the antenna of said radar is unitary,

[0151] - its circularity is equal to the orientation of the longitudinal axis of said track landing expressed in the radar reference and previously obtained from said measurements of said radar;

[0152] - its elevation angle is zero,

[0153] the point Q then being expressed in Cartesian coordinates in said local geographic reference frame by means of said reference frame change matrix, said predetermined angle representative of the error in determining the yaw angle being such that:

[0154] £ _ atan2 yXq ) •

[0155] Indeed, by definition of the predetermined local geographical reference point G', its abscissa axis x should theoretically coincide with the axis of the runway, which then theoretically implies that the orientation of the axis of the runway expressed in the predetermined local geographical reference point G' is zero.

[0156] However, taking into account the specificity of the uncertainty in the inertial measurement of the heading and the risk of imprecision in the orientation of the runway (in particular in the database), the predetermined local geographical reference point G' must be corrected by an angle rotation around the altitude axis z of this reference point so that the X axis of the local geographical reference point is parallel to the axis of the runway in order to meet the objective for which such a reference point is defined.

[0157] Such a rotation 52 when applied then defines a corrected reference frame G” not shown, the origin of which remains O, the phase center of the radar.

[0158] It should be noted that if the geographical orientation of the track is not known (i.e. Upiste= 0 by default), then this rotation correction will determine it.

[0159] As indicated previously, such a rotation is for example applied to the predetermined point corresponding to the middle of the runway or, according to another example, to the point of intersection between two perpendiculars of approach lights, in particular cross-shaped approach lights as referenced in the document of the International Civil Aviation Organization ICAO, Annex 14, Volume I, paragraph 5.3.4.

[0160] Considering the midpoint of the track S, its expression in this corrected reference frame G” is then in the following form: 5^”] = G'2G'' 1 Sjy]

[0161] with: COS (fi, / ;) sm(fiv;) °\ G2G” = -sin(ev,) cos(tv) 0 ' 0 0 J

[0162] and to determine £' / ', as indicated previously, we consider a point Q defined, by its spherical coordinates in the R frame, such that pQ = 1, aQ = y / s / , [3Q = 0 with y / s / the orientation of the axis of the runway expressed in the radar frame R.

[0163] This point Q is then expressed in the frame G', in the same way as for a point P predetermined as described previously and $ _ Xgr ] j '

[0164] It should be noted that yIR / the orientation of the track axis expressed in the radar reference frame R can be obtained according to different variants.

[0165] According to a first variant, the orientation yIRI is obtained by using the aforementioned solution based on learning by artificial intelligence using a deep learning tool based in particular on attention mechanisms applied in a non-trivial manner specifically to radar measurements as described in the patent application whose filing number is FR2309055 in the name of the Applicant. Such learning of the angle y / s / (i.e. in the radar frame of reference R) by artificial intelligence is implemented from the “ground” reality. In particular, in the radar frame of reference R, y!Rl represents the angle formed by the straight line of the axis of the runway with the plane of the circular “0” of the radar.In other words, it is the projection of the runway axis into the (O, x, y) plane of the radar reference frame 62, and the plane of the radar circular "0" is defined as containing the phase center O of the radar antenna and its boresight axis Ox, and is vertical when the radar installation reference is horizontal.

[0166] According to a second variant, the determination of ylRh to be applied at each measurement instant comprises the determination of the three-dimensional geographical position of two points, substantially distant, located on the axis of the runway, typically, the midpoint S of the threshold of said landing runway and the predetermined point P GPIP, by accessing a data platform such as GéoPortail© or GoogleEarth®. From the three-dimensional geographical positions of these two points, the average longitudinal slope Si of the runway between these points and the rppist heading of the runway (i.e. geographical orientation of the runway) are deduced. Then, it is confirmed that the runway does not have a transverse slope st = 0 and failing that, the transverse slope st is then determined. Then, the position of S the midpoint of the threshold of said landing runway and similarly that of the point P the predetermined point GPIP, are determined in an intermediate geographical reference G:

[0167] / ^-Rn\ > = ^Lon ' ^Alt

[0168] with “Lat” representing latitude, “Lon” representing longitude, and “Alt” representing altitude, and from the known definition of the rays terrestrial:

[0169]

[0170] ôLat = Lat (S)- Lat(O), ôLm = Lon (S) - Lon(O), ôAlt = Alt (O)- Alt (S) ^}-e^sin2(Lat) j et nt . RF = .............■■■■■.....— ■ y le^sirt ( Lat ) \ ?

[0171] Lat = = 6378137 m, p2 = 2 - f_f2, j - 298.257223563.

[0172] These positions in the intermediate geographic reference frame G are then brought back into the radar reference frame R such that 5^] — B2R ■ G2B ■ and = B2R ■ G2B ■ P^ with B2R and G2B as previously defined and considering that — ( RP B )1 with the exponent T representing the transpose. The orientation ylRl is then obtained such that

[0173] y = atan2 _ y approximation of arcs by straight lines on the Earth's surface over the radar range which is less than 2,108 m. , and this taking into account the error y - atan2 xSP

[0174] Furthermore, the translation between the origins of the G and G' reference frames is taken into account at the level of the calculation of the deviations as finalized below, and by definition a vector, SP does not depend on the origin of the reference frame.

[0175] According to a third alternative variant of the previous variant, the determination of yIRh comprises the passage of the coordinates of S and P into geocentric coordinates in the ECEF reference frame (from the English earth-centered, earlhfixedy then into local coordinates north, east, down NED (from the English north, east, down) in the geographical reference frame NED local to the radar (in O), then in the R reference frame of the radar, via the matrix GPR — G'2R with st = Si = rppiste = 0), and comprises the calculation of the vector in this Cartesian reference frame of the radar by differentiation of the coordinates,

[0176] Finally, [Fig. 3] illustrates via arrow 84 the last change of reference implemented during the aforementioned step 54 of obtaining the three-dimensional location of said radar expressed in a predetermined reference 86 of the landing runway whose origin is a predetermined point, in particular according to one example the threshold midpoint S of said landing runway and whose two axes correspond respectively to the longitudinal axis and the transverse axis of the runway, said obtaining comprising the inversion of the sign of the component along the axis of the altitudes of said predetermined point of the landing scene expressed in said local geographical reference.

[0177] In other words, this inversion makes it possible in particular to represent the three-dimensional location of the radar of index R expressed in the reference frame 86 of the runway: [xR[runway] \ / \. The runway reference frame 86 is defined such that its origin corresponds, -^Z?[piŸte] I — -Xs'[G ] \^7?[ / ùîff] / \ “As[G ] / according to a first example illustrated by [Fig.3], in the middle S of the runway threshold, its abscissa axis x is along the axis of the runway, oriented positively towards aircraft approaching for landing, its ordinate axis y in the plane of the runway, perpendicular dicular to the abscissa axis, oriented to the right when looking along the abscissa axis, and its altitude axis z such that the reference 86 (S, x, y, z) is direct orthonormal (i.e. downwards if the aircraft is in zero attitude).

[0178] As previously indicated, to reference the position of the radar relative to the GARP and GPIP points, it is sufficient to add respectively DGARP and DGP1P to its abscissa.

[0179] Furthermore, as previously indicated, in the case of an offset runway threshold or radar measurements referenced to an intersection between two perpendiculars of the approach lights, the distance separating the true threshold S from the middle of the offset threshold or the considered intersection of the approach lights || || is added to the abscissa of the position of the radar along the x-axis expressed in the runway reference frame.

[0180] Finally, to reference the position of the aircraft instead of the position of the radar, the radar lever arms relative to the aircraft represented by the vector KO^ with K the reference point of the aircraft of the angular deviations, such as the center of gravity K of the aircraft: KS[cn = with = G2G"B2GXO[b] and such as defined above. The vertical deviation, determined 56 according to the present invention, relative to the track reference in GPIP (i.e. the track reference having GPIP as its origin noted subsequently in the equations [GPIP]) is then expressed in the following form

[0181] / ~Zr\C'PJP] \ Vertical deviation - dv - atan .............-(.---2..........- -GPAG"i

[0182] The lateral deviation, determined 60 according to the present invention, is defined relative to the runway reference in GARP (i.e. the runway reference having GARP as its origin noted subsequently in the equations [GARP]):

[0183] Lateral deviation -ôl = atan ( j

[0184] And to bring these deviations back into the horizontal terrestrial plane at the landing threshold point LTP (from the English landing threshold point) and GARP, the slopes of the runway Si and st are suitable for being taken into account, using the change of reference G 2G with V' — 0, and the vertical offset represented by the difference (GPIP - LTP), is taken into account by reducing the height ZR[runway] as a result of this difference as also introduced in patent FR 3 103 178 in the name of the Applicant.

[0185] Those skilled in the art will understand that the invention is not limited to the embodiments described, nor to the particular examples of the description, the embodiments and variants mentioned above being suitable for being combined with each other to generate new embodiments of the invention.

[0186] The present invention thus makes it possible to precisely determine the elevation of at least one predetermined point of the landing scene in order to improve the accuracy of the subsequent location of the aircraft as such.

[0187] Thanks to this improvement in precision, it is then possible to determine the lateral and vertical angular deviations of the aircraft relative to the ideal final approach trajectory FAS (Final Approach Segment), whatever the attitude of this aircraft, by determining, for example, the middle of the runway threshold S and the orientation F of the runway axis from the radar measurements and according to one of the aforementioned variants, in particular the variant using the aforementioned solution based on learning by artificial intelligence using a deep learning tool based in particular on attention mechanisms applied in a non-trivial manner specifically to radar measurements such as described in the patent application whose filing number is FR2309055 in the name of the Applicant. Then, it is thus possible to bring this information back into the local geographical reference frame at the runway, then to invert the location reference frame (i.e.runway seen from the aircraft relative to the aircraft seen from the runway), then finally to translate this reference point according to the lever arms and the definition of the deviations at the final approach segment FAS.

Claims

1. Claims Method (40) for three-dimensional localization of an aircraft within a landing scene comprising at least one landing runway, said aircraft carrying at least one radar, the landing scene being considered substantially planar in the domain of the angular aperture of said radar, said method comprising at least the following successive steps: - in a predetermined radar reference associated with said radar, the origin of which corresponds to the phase center of the antenna of said at least one radar, obtaining (42) at least: - the distance to the radar and the circular of at least one predetermined point of the landing scene, obtained from measurements of said radar, the circular of said at least one predetermined point corresponding to the angle formed from the line of sight of the radar to the projection of said at least one predetermined point of said landing scene in the plane of projection of the circulars, this plane being defined by the line of sight of the radar, and the axis of the angular measurements of said radar reference mark, and - the distance to the ground in the line of sight of the radar, from the phase center of the antenna of said at least one radar; - determination (44) of a reference change matrix making it possible to pass from said predetermined radar reference to a predetermined local geographical reference whose origin corresponds to the phase center of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll, pitch and yaw angles defining the attitude of the aircraft, these angles being provided beforehand by an inertial unit of the aircraft; - determination (46), in the radar reference frame, of the elevation of said at least one predetermined point of said landing scene, said elevation corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference frame to said at least one predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, said elevation corresponding to the arc sine of the solution of a second degree equation obtained by determining the component of said at least one predetermined point of said landing scene along the axis of altitudes of said local geographical reference frame, both from said distance to the ground in the radar line of sight and of said pitch angle, and from the application of said reference frame change matrix to the coordinates of said at least one predetermined point of the landing scene measured and expressed in said radar reference frame; - determination (48), in said radar reference frame, of the three-dimensional location of said at least one predetermined point of said landing scene, from said radar distance, said circular and said elevation of said at least one predetermined point of said landing scene.

2. The method (40) of claim 1, further comprising the steps of: - determining (50) the three-dimensional location of said at least one predetermined point of said landing scene expressed in said local geographic reference frame by applying said reference frame change matrix to said three-dimensional location of said at least one predetermined point of said landing scene in said radar reference frame; - from the three-dimensional location expressed in the local geographical reference frame, obtaining (54) the three-dimensional location of said radar expressed in a predetermined reference frame of the landing runway whose origin is a predetermined point of said landing runway and whose two axes correspond respectively to the longitudinal axis and to the transverse axis of the runway, said obtaining comprising the inversion of the sign of the component along the axis of the altitudes of said at least one predetermined point of the landing scene expressed in said local geographical reference frame; - determining (56) the vertical angular deviation of said aircraft relative to a reference approach trajectory, using the three-dimensional location of said radar translated along the x-axis from the runway reference to the GPIP point of intersection of the reference approach trajectory with the landing runway; - determining (60) the lateral angular deviation of said aircraft relative to the reference approach trajectory, using the three-dimensional location of said radar, translated along the x-axis from the runway reference to the GARP reference point for determining the lateral deviations.

3. Method (40) according to claim 1 or 2, wherein said at least one predetermined point of said landing scene corresponds to the threshold midpoint S of said landing runway.

4. Method (40) according to claim 2, in which said at least one predetermined point of said landing scene corresponds to a point of intersection A of two lines of approach lights perpendicular to each other, and in which the norm of the vector going from said point of intersection A to the middle S of the threshold of said landing runway is also taken into account (58), when determining (56) the vertical angular deviation and the lateral angular deviation, by translating, from said norm, the position of said radar, expressed in the predetermined reference of said runway along the x axis.

5. Method (40) according to any one of claims 1 to 4, wherein said determination (44) of a reference frame change matrix comprises three successive reference frame changes, namely: - a first reference frame change (68) from the radar reference frame (62) to the aircraft reference frame (70) used by said inertial unit to provide the roll, pitch and yaw angles defining the attitude of the aircraft, using the inclination of said radar; then - a second reference frame change from the aircraft reference frame (70) to an intermediate geographical reference frame having: an origin corresponding to the phase center of the antenna of said radar, an abscissa axis along the terrestrial geographic North direction, an ordinate axis along the terrestrial geographic East direction and an altitude axis along the terrestrial geographic local vertical;- a third change of reference from the intermediate geographical reference to said predetermined local geographical reference (80) defined relative to the plane of the landing scene.;

6. Method (40) according to any one of the preceding claims, further comprising, prior to obtaining (54) the three-dimensional location of said radar expressed in a predetermined reference frame of the landing runway, applying a rotation (52) around the altitude axis of the local geographical reference frame according to a predetermined angle representative of the error in determining the yaw angle V' by said inertial unit of the aircraft, said predetermined angle representative of the error in determining the yaw angle being obtained, prior to applying said rotation, from a point Q defined by its spherical coordinates in the radar reference frame, such that: - its distance from the phase center of the antenna of said radar is unitary, - its circularity is equal to the orientation of the longitudinal axis of said landing runway expressed in the radar reference frame and previously obtained from said measurements of said radar; - its elevation angle is zero, point Q then being expressed in Cartesian coordinates in said local geographic reference frame by means of said reference frame change matrix, said predetermined angle representative of the error in determining the yaw angle being such that _ atan2^ v

7. A computer program comprising software instructions which, when implemented by a programmable electronic device, implement a method for determining the vertical and horizontal angular deviations of an aircraft according to claims 1 to 6.

8. Electronic device (10) for three-dimensional location of an aircraft within a landing scene comprising at least one landing runway, said aircraft carrying at least one radar, the landing scene being considered substantially planar in the domain of the angular aperture of said radar, characterized in that said device comprises: - a first module (12) configured to implement, in a predetermined radar reference associated with said radar, the origin of which corresponds to the phase center of the antenna of said at least one radar, the obtaining of at least: - the distance to the radar and the circular of at least one predetermined point of the landing scene, obtained from measurements of said radar, the circular of said predetermined point of said landing scene corresponding to the angle formed from the line of sight of the radar to the projection of said at least one predetermined point in the plane of projection of the circulars,this plane being defined by the radar sighting axis and the axis of the angular measurements of said radar reference frame, and - the distance to the ground, in the radar sighting axis, from the phase center of the antenna of said at least one radar; - a second module (14) configured to determine a reference frame change matrix making it possible to pass from said predetermined radar reference frame to a predetermined local geographical reference frame whose origin corresponds to the phase center of the antenna of said radar and whose two axes correspond respectively to the longitudinal axis and the transverse axis of said landing runway, using the roll and pitch angles, and yaw defining the attitude of the aircraft, these angles being provided beforehand by an inertial unit of the aircraft; - a third module (16) configured to determine, in the radar reference frame, the elevation of said at least one predetermined point of said landing scene, said elevation corresponding to the opposite of the angle formed from the vector starting from the origin of the radar reference frame to said at least one predetermined point of said landing scene, up to the projection of this vector in the projection plane of the circulars, said elevation corresponding to the arc sine of the solution of a second degree equation obtained by determining the component of said at least one predetermined point of said landing scene along the axis of altitudes of said local geographical reference frame, both from said distance to the ground in the radar line of sight and from said pitch angle, and from the application of said reference frame change matrix to the coordinates of said at least one predetermined point of the landing scene measured and expressed in said radar reference frame; - a fourth module (18) configured to determine, in said radar reference frame, the three-dimensional location of said at least one predetermined point of said landing scene, from said radar distance, said circular and said elevation of said at least one predetermined point of said landing scene.

9. Aircraft landing assistance system comprising at least one radar and one electronic three-dimensional location device according to claim 8.

10. Aircraft comprising an inertial unit and a landing aid system according to claim 9.

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