Method for detecting an airport comprising a landing zone, and associated automatic take-off or landing method

Abstract

The present invention relates to a method for detecting an airport (10) comprising a landing zone (12) and provided with reflectors (14) configured to reflect an incident electromagnetic wave, each reflector (14) having a polarization-rotating property. The method comprises the following steps: - an aircraft (18) approaches the airport (10) or the aircraft (18) is present in the airport (10), the aircraft (18) being provided with at least one radar, - the at least one radar emits a signal having an initial polarization, - the at least one radar receives a reflected signal, and - the presence and, where applicable, the respective location of the reflectors (14) is determined based on the polarization of the reflected signal. The invention also relates to an associated automatic take-off or landing method.

Description

[0001] Method for detecting an airport including a landing area, and associated method for automatic takeoff or landing

[0002] The present invention relates to a method for detecting an airport comprising a landing area, and an associated method for automatic takeoff or landing.

[0003] Here, an airport is defined as the facilities that allow the landing, takeoff and ground maneuvers of an aircraft.

[0004] A system within the framework of an automatic landing until touchdown is the Category III Instrument Landing System, or ILS CAT II, ​​according to the ICAO Convention - Annex 10 in force in June 2024.

[0005] This system includes important airport facilities, including a location set, such as a runway alignment radio beacon, to provide the aircraft's deviation from the runway centerline, and a so-called glide path set, or descent path, to provide the aircraft's deviation from the nominal approach slope.

[0006] This presents a very high installation cost for the airport, as well as for its operation, so such a system is limited to large airports, which are able to make such investments.

[0007] Alternatively, another system includes a ground reinforcement system or Ground Based Augmentation System (G BAS).

[0008] Such a system also requires significant infrastructure, and presents the same disadvantages as the CAT III ILS.

[0009] Other systems, such as the Satellite-Based Augmentation System (SBAS), are not sufficient both in terms of positioning accuracy and especially availability (particularly due to sensitivity to jamming, and the effects of multipath propagation which become increasingly important as one approaches the ground) to assist in the context of an automatic landing up to wheel touchdown.

[0010] The aim of the invention is therefore to propose a method for locating an aircraft, without requiring significant infrastructure, with sufficient precision, in particular to allow automatic guidance of the aircraft until it touches down.

[0011] To this end, the invention relates to a method for detecting an airport comprising a landing zone, the airport being equipped with a plurality of reflectors, each reflector being configured to reflect an electromagnetic wave incident on said reflector and having an incident polarization, each reflector having a polarization rotation property, such that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the method comprising the following steps:

[0012] - approach to the airport by an aircraft or presence of the aircraft at the airport, the aircraft being equipped with at least one radar,

[0013] - emission by at least one radar of a signal exhibiting an initial polarization,

[0014] - reception by at least one radar of a reflected signal, the at least one radar being capable of receiving waves with a polarization orthogonal to the initial polarization, and

[0015] - determination of the presence and, where applicable, the respective location of reflectors from the polarization of the reflected signal.

[0016] The port installation includes the reflectors, which represents a limited amount of equipment, thus allowing for widespread deployment of this solution. The equipment on board the aircraft is also minimal and does not add significant weight. Furthermore, this process enables the aircraft to accurately detect the reflectors, thereby determining its position relative to the airport, and for example, to the landing zone.

[0017] According to other advantageous aspects of the invention, the method comprises one or more of the following features, taken individually or in all technically possible combinations:

[0018] - the process further includes a step of determining the location of the landing zone in relation to the aircraft from the determined location of the reflectors, in the event that the presence of reflectors has been determined;

[0019] - the determination of presence includes a measurement of the power of the component of the reflected signal exhibiting orthogonal polarization;

[0020] - at least one radar is capable of receiving waves of the initial polarization and waves of polarization orthogonal to the initial polarization;

[0021] - the determination of presence includes a measurement of a parameter of the component of the reflected signal exhibiting orthogonal polarization, a measurement of a parameter of the component of the reflected signal exhibiting the initial polarization, a calculation of the ratio of the parameter of the component of the reflected signal exhibiting orthogonal polarization to the parameter of the component of the reflected signal exhibiting the initial polarization, and a comparison of the ratio with a threshold;

[0022] - at least one radar is also capable of emitting waves having a second initial polarization, the second initial polarization corresponding to the orthogonal polarization of the initial polarization, the process comprising a step of emission by at least one radar of a signal having the second initial polarization;- the determination of presence includes a measurement of the power of the component of the reflected signal having the initial polarization from the signal having the second initial polarization, a measurement of the power of the component of the reflected signal having the orthogonal polarization from the signal having the second initial polarization, a calculation of a second ratio of said power for the component having the initial polarization to said power of the component of the reflected signal having the second initial polarization, and a comparison of the ratio with the threshold, a reflector being detected only when the ratio and the second ratio are greater than the threshold;

[0023] - at least one radar includes a frequency-modulated continuous wave radar;

[0024] - each reflector has a radar cross-sectional area such that each reflector is distinguishable from the rest of the airport; and / or

[0025] - reflectors surround the landing area.

[0026] The invention also relates to a method for the automatic takeoff or landing of an aircraft from or on a landing area of ​​an airport, the airport being provided with a plurality of reflectors, each reflector being configured to reflect an electromagnetic wave incident on said reflector and having an incident polarization, each reflector having a polarization rotation property, so that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the automatic takeoff or landing method comprising an airport detection step according to the method described above.

[0027] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0028] [Fig. 1] Figure 1 is a schematic partial top view of an airport according to a first example embodiment,

[0029] [Fig 2] Figure 2 is a schematic top view of an airport according to a second example embodiment,

[0030] [Fig 3] Figure 3 is a schematic view of the steps in the detection process according to one embodiment of the invention, and

[0031] [Fig 4] Figure 4 is a schematic view of some elements of an aircraft according to an example embodiment.

[0032] The invention relates to a method for detecting an airport comprising a landing zone.

[0033] Examples of airports according to the method of the invention are shown in Figures 1 and 2. Similar or identical elements are numbered in Figure 2 with the same numerical reference as in Figure 1, incremented by 100.

[0034] Airport 10, 110 includes a landing area of ​​12, 112.

[0035] Landing zone 12, 112 allows for aircraft landing and takeoff.

[0036] Landing area 12 includes, for example, a landing strip, as shown in Figure 1, extending along a longitudinal direction X.

[0037] The runway 12 then presents, for example, a location 13 for wheel touchdown, said location being an area in which an aircraft is supposed to touch down on the ground at wheel level during its landing.

[0038] The airport is then adapted for airplanes.

[0039] The trail includes, for example, at least one identifiable region.

[0040] More specifically, the track here includes a start region D, a central region C, and an end region, with the start region D and the end region being identifiable regions.

[0041] The starting region D, the central region C and the ending region F are aligned in that order along the longitudinal direction X.

[0042] The track is symmetrical here, with respect to a median plane P, perpendicular to the longitudinal direction X.

[0043] Thus, the track is likely to be used in two directions.

[0044] Alternatively, airport 110 includes, for example, a vertiport.

[0045] The vertiport is suitable for helicopters.

[0046] Landing zone 112 then has, for example, the shape of a disc.

[0047] Alternatively, landing zone 112 has, for example, the shape of a regular polygon.

[0048] Airport 10, 110 is equipped with a plurality of reflectors 14, 114.

[0049] In the case of a runway, airport 10 is, for example, equipped with at least one pair of reflectors 14. In the case of a vertiport, airport 110 is, for example, equipped with at least three reflectors 114.

[0050] Each reflector 14, 114 is configured to reflect an electromagnetic wave incident on said reflector and having an initial polarization.

[0051] Each reflector 14, 114 exhibits a polarization rotation property, such that the reflected wave predominantly has a polarization orthogonal to the initial polarization of the incident wave, that is to say that the polarization of at least 50% of the incident wave is transformed into orthogonal polarization by reflection on said reflector 14, 114. More particularly here, each reflector 14, 114 is such that the polarization of at least 80%, here at least 90%, of the incident wave is transformed into a polarization orthogonal to the polarization of the incident wave, by reflection on said reflector 14, 114.

[0052] Each reflector is designed to be distinguishable from the rest of the airport by radar.

[0053] Each reflector has a radar cross-section (RCS).

[0054] The radar cross-sectional area is such that each reflector is distinguishable from the rest of the airport by radar, in particular from the ground including tar and / or vegetation of the airport.

[0055] The radar cross-sectional area is, for example, greater than or equal to 10 times the radar cross-sectional area of ​​other airport elements, and in particular of the clutter formed by the ground.

[0056] Reflectors 14, 114 surround landing zone 12, 112 here.

[0057] More specifically, reflectors 14, 114 are arranged outside landing zone 12, 112.

[0058] Landing zone 12, 112 here presents two sides with respect to a transverse direction Y.

[0059] Airport 10, 110 is equipped with reflectors 14, 114 on each side of landing area 12, 112.

[0060] In the case of a runway, the sides correspond to the lateral sides of the runway.

[0061] The reflectors 14 are, for example, arranged symmetrically on either side of the track, more particularly according to an orthogonal symmetry with respect to a central axis of the track.

[0062] The reflectors 14 are, for example, further distributed along a longitudinal direction X of the runway, more particularly of at least one identifiable region.

[0063] Reflectors 14 are, for example, arranged on either side of the track along the transverse direction Y at location 13.

[0064] The reflectors 14 form, for example, at least one pattern 16, more particularly of a plurality of reflectors 14.

[0065] Each pattern 16 includes, for example, at least two reflectors 14.

[0066] In one embodiment, more specifically in the case of a runway, each pattern 16 is formed of four reflectors arranged in two lines, the lines being along the transverse direction Y. The reflectors of the two lines are staggered. Here, the reflectors 14 form a plurality of identical patterns, distributed along the runway along the longitudinal direction X, more specifically in at least one identifiable region, and on either side of the runway along the transverse direction Y.

[0067] More specifically here, the patterns are distributed along at least one identifiable region at regular intervals along the longitudinal direction X, on either side of the track along the transverse direction Y.

[0068] The patterns are set far apart from the runway side, so that the distance between the patterns and the longitudinal centerline is constant, for example between 25 m and 100 m.

[0069] In the case of a vertiport, the reflectors 114 are, for example, arranged in the form of two lines, each line extending from one side of the vertiport along the transverse direction Y.

[0070] Each line of reflectors includes, for example, at least three reflectors, here at least four, more specifically four, 114 reflectors.

[0071] The reflector lines are equidistant with respect to a central line.

[0072] The reflector lines are, for example, in the example shown, arranged symmetrically on either side of landing zone 112, more particularly with respect to a plane of symmetry.

[0073] Alternatively, the reflectors of the reflector lines are, for example, arranged in a staggered pattern.

[0074] The median line is defined here as the line connecting the midpoints of the two reflector lines.

[0075] The reflectors are arranged so that the center of landing zone 112 corresponds to the intersection between the central line and the median line.

[0076] The detection process will now be described with reference to Figure 3.

[0077] The detection process includes the approach 210 of airport 10, 110 by an aircraft 18, 118, in particular for a landing on the landing area, or the presence of the aircraft 18, 118 in airport 10, 110, in particular for a takeoff from the landing area.

[0078] An example of certain elements of an aircraft according to an embodiment of the invention is schematically represented in Figure 4.

[0079] The aircraft is equipped with at least one 310 radar.

[0080] At least one 310 radar includes, for example, a frequency-modulated continuous wave radar.

[0081] The radar 310 here includes at least one antenna, here two antennas 312, 314, more particularly a transmitting antenna 312 and a receiving antenna 314. Alternatively, the radar includes a single antenna capable of transmitting and receiving electromagnetic waves.

[0082] The 310 radar is capable of emitting a signal with an initial polarization.

[0083] The 310 radar is capable of receiving waves with a polarization orthogonal to the initial polarization.

[0084] In a particular embodiment, the radar 310 is also capable of receiving waves of orthogonal polarization and waves of initial polarization.

[0085] In this particular embodiment, the radar 310 is, for example, also capable of emitting waves having a second initial polarization, the second initial polarization corresponding to the orthogonal polarization.

[0086] The 310 radar has a frequency band, between the X and W bands, for example between 10 GHz and 100 GHz.

[0087] The 310 radar, for example, has a radial range resolution of between 60 cm and 3 m.

[0088] The 310 radar, for example, has an angular resolution of less than 3°, more specifically between 1° and 2°.

[0089] The 310 radar, for example, has a range of between 350 m and 5 km.

[0090] In the example in Figure 4, the aircraft includes an information processing unit consisting, for example, of a memory 312 and a processor 314 associated with the memory 312.

[0091] The aircraft further includes here, for example, a measurement module 316, the measurement module 316 being capable of measuring at least one parameter of the orthogonal polarization component of a wave received by the radar, and, where appropriate, of the initial polarization component of a wave received by the radar.

[0092] At least one parameter includes, for example, power.

[0093] The aircraft also includes a 318 determination module.

[0094] The determination module is capable of determining the presence and, where applicable, the relative location of reflector(s) relative to the aircraft from the polarization of the signal received by the radar 310, as will be described below.

[0095] The determination module is, for example, also capable of determining the location of the landing zone 12 in relation to the aircraft 18.

[0096] In the example shown in Figure 4, the determination module 318, and optionally the measurement module 316, are each implemented as a software program, or software component, executable by the processor 314. The memory 312 is then capable of storing a determination program, and optionally a measurement program. The processor is then capable of executing each of the programs. In an alternative (not shown), the determination module, and optionally the measurement module, are each implemented as a programmable logic component, such as an FPGA (Field Programmable Gate Array), or an integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0097] When modules are implemented as one or more software programs, that is, as a computer program, also called a computer program product, it is also capable of being stored on a computer-readable medium (not shown here). A computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. Examples of such a readable medium include an optical disc, a magneto-optical disc, ROM, RAM, any type of non-volatile memory (e.g., FLASH or NVRAM), or a magnetic card. A computer program containing software instructions is then stored on this readable medium.

[0098] The process also includes the following steps:

[0099] - emission 212 by at least one radar 310, more particularly via the transmitting antenna 312, of a signal exhibiting an initial polarization,

[0100] - reception 214 by at least one radar 310, more particularly via the receiving antenna 314, of a reflected signal, and

[0101] - determination of the presence 216 and, where applicable, of the respective location of the reflector from the polarization of the reflected signal, more particularly by the determination module 318.

[0102] The presence determination step 216 includes, for example, a measurement substep 218 and an application substep 220 of at least one criterion.

[0103] The process includes, for example, in addition a step of determining the location 222 of the landing area 12, 112 in relation to the aircraft 18, 118, in the event of determination of the presence of reflectors, more particularly by the determination module 318.

[0104] In a first embodiment of the process, the signal emitted by at least one radar 310 has only the initial polarization.

[0105] When the signal reaches a reflector 14, 114, the reflector reflects the signal, so that the polarization of at least 50%, more particularly at least 80%, more particularly at least 90%, of the wave incident on said reflector is transformed into orthogonal polarization by reflection on said reflector 14, 114.

[0106] The rest of the airport also reflects the incident wave, but does not exhibit polarization rotation properties or polarization rotation properties strictly less important than reflectors 14, 114. During reception 214, radar 310 receives the waves reflected by the airport, including the reflectors.

[0107] Here, in the first embodiment, the radar 310 is capable of receiving waves of the polarization orthogonal to the initial polarization.

[0108] The determination of the presence and, where applicable, the respective location of the reflectors, here in relation to the aircraft, is carried out by distinguishing the elements which have particularly reflected by crossing the polarization, that is to say by transforming the initial polarization into a polarization orthogonal to said initial polarization, which is received here by the radar 310.

[0109] Measurement 218 includes the measurement of at least one parameter, here the reflected power, or in other words the amplitude of the received signal, of the orthogonal polarization component of the signal received by radar 310.

[0110] Alternatively, at least one parameter includes, more specifically, the Doppler velocity equal to the projection of the carrier velocity vector onto a radar-reflector axis.

[0111] The application of at least one criterion (220) includes, for example, comparing the measured parameter, in this case power, with a predetermined threshold. If the measured power is greater than or equal to the predetermined threshold, then a reflector is detected at the corresponding location. If the measured reflected power is strictly less than the predetermined threshold, then it is determined that no reflector is detected at the location.

[0112] The threshold is, for example, linked to the power contrast with the surrounding medium, for example equal to the average power reflected by the surrounding medium multiplied by a given number.

[0113] Alternatively, the threshold is, for example, a given portion of the signal power emitted by the radar 310.

[0114] In the event of detection of reflectors 14, 114, the step of determining the location 222 of the landing zone 12, 112, here in relation to the aircraft, is carried out from the respective location determined of reflectors 14, 114.

[0115] For example, one or more reflector location configurations relative to a landing area are pre-recorded in the aircraft, more specifically in memory 312.

[0116] The location determination step 222 involves comparing the determined reflector locations with the previously recorded configuration(s). When the determined locations match a previously recorded configuration, then the landing zone location determined during the location determination step 222 corresponds to the landing zone location in the corresponding configuration.

[0117] Alternatively, the location of the landing zone 12, 112 is determined as the area delimited by the reflectors 14, 114 by removing a given margin, for example of a given distance.

[0118] Alternatively, in the case of a vertiport, the center of landing zone 112 is calculated as the intersection between the center line between the reflector lines and the median line, as described previously.

[0119] The location of the landing zone is then, for example, determined as the circle centered on the calculated center and having a given diameter.

[0120] Alternatively, in the case of a vertiport, the center of the landing area 112 is calculated as the isobarycenter of the respective locations of the reflectors 114.

[0121] If the presence of reflectors is not determined during step 216, then the process is, for example, repeated from emission step 212.

[0122] This first embodiment allows a very good level of confidence in the detection of reflectors, and thus of the landing zone, for different types of landing zone.

[0123] This is particularly advantageous in dense environments, improving robustness to saturation, for example, while increasing contrast and identification.

[0124] Such a solution is also economical in terms of size, weight and power to be carried in the aircraft.

[0125] In a second embodiment of the process, the signal emitted by at least one radar 310 has only the initial polarization.

[0126] When the signal reaches a reflector 14, 114, the reflector reflects the signal, so that the polarization of at least 50%, more particularly at least 80%, more particularly at least 90%, of the wave incident on said reflector is transformed into a polarization orthogonal to the initial polarization by reflection on said reflector 14, 114.

[0127] The rest of the airport also reflects the incident wave, but does not exhibit polarization rotation properties or has strictly less polarization rotation properties than reflectors 14, 114.

[0128] During reception 214, radar 310 receives waves reflected by the airport, including reflectors 14, 114. Here, in the second embodiment, radar 310 is capable of receiving waves of the initial polarization and of the polarization orthogonal to the initial polarization.

[0129] The determination of the presence and, where applicable, the respective location of the reflectors, here in relation to the aircraft, is carried out by distinguishing the elements that have particularly reflected by crossing the polarization with respect to the reflection without change of polarization, which are received here by the radar 310.

[0130] Measurement 218 includes the measurement of at least one parameter, here the reflected power, of the orthogonal polarization component of the signal received by radar 310 and of the initial polarization component of the signal received by radar 310.

[0131] The application of at least one criterion includes, for example, a calculation of the ratio r of the parameter of the reflected signal component exhibiting orthogonal polarization to the parameter of the reflected signal component exhibiting the initial polarization, and a comparison of the ratio with a threshold.

[0132] The ratio r is thus equal toav ec S cross .p O | the parameter of the component of reflected signal exhibiting orthogonal polarization and S C0 .p0| the parameter of the reflected signal component exhibiting the initial polarization.

[0133] Here, if the ratio is greater than or equal to the threshold, then a reflector is detected at the corresponding location. If the ratio is strictly less than the threshold, then no reflector is detected at the location.

[0134] The threshold is, for example, strictly greater than 1, for example strictly greater than 5, for example equal to 10.

[0135] The threshold is, for example, predetermined.

[0136] In the event of detection of reflectors, the step of determining the location 222 of the landing zone 12, 112, here in relation to the aircraft, is, for example, carried out similarly as in the first embodiment of the method of the invention.

[0137] The process also includes, for example, the detection of at least one obstacle in the landing area.

[0138] More specifically, the process includes, for example, the detection of an object from the signal received by the radar 310, more specifically the object being detected in the determined landing area, the ratio for the object being less than the threshold above.

[0139] The object is then detected as an obstacle.

[0140] If the presence of reflectors is not determined during step 216, then the process is, for example, repeated from emission step 212.

[0141] This second embodiment provides a very high level of confidence in the detection of reflectors, and thus of the landing zone, particularly for different types of landing zones. This is especially advantageous in dense environments, as mentioned previously. Furthermore, compared to the first embodiment, it enables the detection of obstacles in the landing zone.

[0142] In a third embodiment of the process, the signal emitted by at least one radar 310 has the initial polarization, referred to as the first initial polarization hereafter, and a second initial polarization, corresponding to the polarization orthogonal to the first initial polarization.

[0143] The signal includes, for example, a first portion exhibiting the first initial polarization and a second portion exhibiting the second initial polarization.

[0144] The first portion and the second portion are, for example, emitted successively in time.

[0145] Alternatively, they are emitted simultaneously. The first and second portions of the signal are then distinguishable, for example by their frequency or orthogonal phase codings.

[0146] When the signal reaches a reflector 14, 114, the reflector reflects the signal, so that the polarization of at least 50%, more particularly at least 80%, more particularly at least 90%, of the wave incident on said reflector is transformed by reflection on said reflector 14, 114, more particularly from the first initial polarization to the second orthogonal polarization and from the second initial polarization to the first initial polarization.

[0147] The rest of the airport also reflects the incident wave, but does not exhibit polarization rotation properties or has strictly less polarization rotation properties than reflectors 14, 114.

[0148] During reception 214, radar 310 receives waves reflected by the airport, including reflectors.

[0149] Here, in the third embodiment, the radar 310 is capable of receiving waves of the first initial polarization and of the polarization orthogonal to the first initial polarization, that is to say here the second initial polarization.

[0150] The determination of the presence and, where applicable, the respective location of the reflectors, here in relation to the aircraft, is carried out by distinguishing the elements that have particularly reflected by crossing the polarization with respect to the reflection without change of polarization, which are received here by the radar 310.

[0151] Measurement 218 includes the measurement of at least one parameter, here the reflected power, of the orthogonal polarization component of the signal received by radar 310 and of the initial polarization component of the signal received by radar 310.

[0152] More specifically, the first and second signal portions are distinguished from one another. Measurement 218 includes the measurement of at least one parameter, here the reflected power, for each of the following components:

[0153] - the orthogonal polarization component, i.e. exhibiting the second initial polarization, of the signal received by the radar 310 corresponding to the reflection of the first portion,

[0154] - the initial polarization component, i.e. exhibiting the first initial polarization, of the signal received by the radar 310 corresponding to the reflection of the first portion,

[0155] - the orthogonal polarization component, i.e., exhibiting the second initial polarization, of the signal received by the radar 310 corresponding to the reflection of the second portion, and

[0156] - the initial polarization component, i.e. presenting the first initial polarization, of the signal received by the radar 310 corresponding to the reflection of the second portion.

[0157] The application of at least one criterion includes, for example, a calculation of two ratios and a comparison of the ratios with a threshold.

[0158] The first ratio r1 is equal to the ratio of the parameter of the component of the reflected signal exhibiting the orthogonal polarization corresponding to the reflection of the first portion to the parameter of the component of the reflected signal exhibiting the initial polarization corresponding to the reflection of the first portion.

[0159] The second ratio r2 is equal to the ratio of the parameter of the component of the reflected signal exhibiting the initial polarization corresponding to the reflection of the second portion to the parameter of the component of the reflected signal exhibiting the orthogonal polarization corresponding to the reflection of the second portion.

[0160] The ratio r1 is thus equal with S cr oss-poii the parameter of the component of the reflected signal exhibiting the orthogonal polarization corresponding to the reflection of the first portion, which therefore corresponds to the signal having a cross polarization with respect to the incident polarization of the first portion, and S C o- P oii is the parameter of the reflected signal component exhibiting the initial polarization corresponding to the reflection of the first portion, which therefore corresponds to the signal having a co-polarization with respect to the incident polarization of the first portion. > ' < ii

[0161] The ratio r2 is equal to a - - , with S cross .poi2le parameterized by the component of the reflected signal exhibiting the initial polarization corresponding to the reflection of the second portion, which therefore corresponds to the signal having a cross polarization with respect to the incident polarization of the second portion, and S co .poi2le is the parameter of the reflected signal component exhibiting the orthogonal polarization corresponding to the reflection of the second portion, which therefore corresponds to the signal having a co-polarization with respect to the incident polarization of the second portion. Here, if each of the ratios is greater than or equal to the threshold, then a reflector is detected at the corresponding location.

[0162] If both ratios are strictly below the threshold, then no reflector is detected at the location.

[0163] If one ratio is greater than or equal to the threshold, and the other ratio is strictly less than the threshold, then no reflector is detected at the location.

[0164] The threshold is, for example, greater than 1, for example strictly greater than 5, for example equal to 10.

[0165] The threshold is, for example, predetermined.

[0166] In the event of detection of reflectors, the step of determining the location 222 of the landing zone 12, 112, here in relation to the aircraft, is, for example, carried out similarly as in the first embodiment of the method of the invention.

[0167] The process also includes, for example, the detection of at least one obstacle in the landing area.

[0168] More specifically, the process includes, for example, the detection of an object from the signal received by the radar 310, one of the reports for the object being below the threshold above.

[0169] The object is then detected as an obstacle.

[0170] This third embodiment provides a form of redundancy with respect to the second embodiment, and allows for an excellent level of confidence in distinguishing reflectors, and thus the landing zone, for different types of landing zones. This is particularly advantageous in dense environments.

[0171] The invention further relates to a method for the automatic takeoff or landing of an aircraft from or on a landing area of ​​an airport as described above.

[0172] In the case of a landing, the aircraft approaches the airport.

[0173] In the case of a takeoff, the aircraft is present in the airport, on the ground.

[0174] The automatic takeoff or landing procedure includes an airport detection step according to the procedure as described previously.

[0175] The aircraft thus detects the location of the reflectors, and therefore the landing zone.

[0176] The method then includes, for example, a takeoff step from the landing area, with the aircraft being automatically controlled from a predetermined location within the landing area. Alternatively, the method includes a landing step on the landing area, with the aircraft being automatically controlled from a predetermined location within the landing area, specifically until the aircraft's wheels touch down on the landing area. Reflector detection allows the aircraft's location relative to the landing area to be determined, specifically the distances along the longitudinal, transverse, and vertical directions, or the distance, angle of descent, and alignment along the transverse Y direction for an airplane.

Claims

DEMANDS 1. A method for detecting an airport (10; 110) comprising a landing area (12; 112), the airport (10; 110) being provided with a plurality of reflectors (14; 114), each reflector (14; 114) being configured to reflect an electromagnetic wave incident on said reflector (14; 114) and having an incident polarization, each reflector (14; 114) having a polarization rotation property, such that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the method comprising the following steps: approach (210) of the airport (10; 110) by an aircraft (18; 118) or presence of the aircraft (18; 118) in the airport (10; 110), the aircraft (18;118) being equipped with at least one radar (310), emission (212) by the at least one radar (310) of a signal having an initial polarization, reception (214) by the at least one radar (310) of a reflected signal, the at least one radar (310) being capable of receiving waves of a polarization orthogonal to the initial polarization, and determination of the presence (216) and, where applicable, the respective location of the reflectors (14; 114) from the polarization of the reflected signal.; 2. Method according to claim 1, further comprising a step of determining the location (222) of the landing zone (12; 112) relative to the aircraft (18; 118) from the determined location of the reflectors (14; 114), in the event of determination of the presence of reflectors.

3. Method according to claim 1 or 2, wherein the determination of the presence (216) includes a measurement (218) of the power of the component of the reflected signal exhibiting orthogonal polarization.

4. A method according to any one of claims 1 to 3, wherein at least one radar (310) is capable of receiving waves of the initial polarization and waves of the polarization orthogonal to the initial polarization.

5. A method according to claim 4, wherein the determination of the presence (216) comprises a measurement of a parameter of the component of the reflected signal having orthogonal polarization, a measurement of a parameter of the component of the reflected signal having the initial polarization, a calculation of the ratio of the parameter of the component of the reflected signal having orthogonal polarization to the parameter of the component of the reflected signal showing the initial polarization, and a comparison of the ratio with a threshold.

6. Method according to claim 4 or 5, wherein at least one radar (310) is further capable of emitting waves having a second initial polarization, the second initial polarization corresponding to the orthogonal polarization of the initial polarization, the method comprising a step of emitting by at least one radar (310) a signal having the second initial polarization.

7. Method according to claim 6, wherein the signal comprises a first portion having the first initial polarization and a second portion having the second initial polarization emitted successively in time or simultaneously, in which case the first portion and the second portion of the signal are then distinguishable, for example, by their frequency or orthogonal phase codings.

8. A method according to claims 5 and 7, wherein the determination of the presence (216) comprises: - the measurement of at least one parameter for each of the following components: the orthogonal polarization component of the signal received by the radar corresponding to the reflection of the first portion, the initial polarization component of the signal received by the radar corresponding to the reflection of the first portion, the orthogonal polarization component of the signal received by the radar corresponding to the reflection of the second portion, and the initial polarization component of the signal received by the radar corresponding to the reflection of the second portion, - a calculation of a first ratio of the orthogonal polarization component of the signal received by the radar corresponding to the reflection of the first portion to the initial polarization component of the signal received by the radar corresponding to the reflection of the first portion, and a comparison of the ratio with a threshold, and - a calculation of a second ratio of the orthogonal polarization component of the signal received by the radar corresponding to the reflection of the second portion to the initial polarization component of the signal received by the radar corresponding to the reflection of the second portion, and a comparison of the second ratio with the threshold; a reflector (14; 114) being detected only when the ratio and the second ratio are greater than the threshold 9. A method according to claim 8, wherein the determination of the presence (216) comprises a measurement of the power of the component of the reflected signal having the initial polarization from the signal having the second polarization 18. Initially, a measurement of the power of the component of the reflected signal exhibiting the orthogonal polarization from the signal exhibiting the second initial polarization and a calculation of the second ratio of said power for the component exhibiting the initial polarization to said power of the component of the reflected signal exhibiting the second initial polarization, and a comparison of the ratio with the threshold.

10. A method according to any one of claims 1 to 9, wherein at least one radar (310) comprises a frequency-modulated continuous wave radar.

11. A method according to any one of claims 1 to 10, wherein each reflector (14; 114) has a radar cross-sectional area such that each reflector is distinguishable from the rest of the airport.

12. Method according to any one of claims 1 to 11, wherein the reflectors (14; 114) surround the landing area (12; 112).

13. Method for the automatic takeoff or landing of an aircraft (18; 118) from or on a landing area (12; 112) of an airport (10; 110), the airport (10; 110) being provided with a plurality of reflectors (14; 114), each reflector (14; 114) being configured to reflect an electromagnetic wave incident on said reflector (14; 114) and having an incident polarization, each reflector (14; 114) having a polarization rotation property, such that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the method for automatic takeoff or landing comprising a step of detecting the airport (10; 110) according to the method according to any one of claims 1 to 12.

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