Anti-decoy device and method for aircraft by analyzing data from geolocation satellite triplets.

Abstract

TITLE: Anti-decoy device and method for aircraft by analyzing data from triplets of geolocation satellites. Satellite geolocation device and method for calculating the position of a point P of an aircraft, in real time, with high precision and this even in the presence of one or more decoy emissions or emissions from malfunctioning satellites, by analyzing the data provided by a set of triplets of geolocation satellites and depending on the coincidence or non-coincidence of the points obtained from these said triplets of satellites. Figure for the abstract: Fig. 1

Description

Title of the invention: Anti-decoy device and method for aircraft by analyzing data from geolocation satellite triplets.

[0001] The present invention relates to an anti-decoy device and method for aircraft by analyzing data provided by a set of triplets of geolocation satellites.

[0002] The present invention relates to a device and a method for obtaining the position of an aircraft in a precise and reliable manner.

[0003] It also relates to a device and a method for defining and countering decoy attacks.

[0004] It also makes it possible to determine decoy satellites among the constellations of geolocation satellites.

[0005] It also makes it possible to determine which satellites are faulty and / or providing erroneous information among the constellations of geolocation satellites.

[0006] The invention finds its particular utility in the aeronautical field where knowledge of the parameters linked to the position is fundamental and where the reliability of this information must be exceptionally high. The possibilities of deception currently make existing geolocation technologies, particularly for civil aircraft, unattractive given the potential risks of deception and in fact reduces the overall reliability of this technology to a level which makes this technology unacceptable for so-called critical uses.

[0007] Global Navigation Satellite Systems (GNSS) spoofing is a technique used to disrupt or deceive GNSS receivers. This can have serious consequences, as many vital systems and applications depend on the positioning accuracy provided by GNSS satellite navigation systems.

[0008] It is therefore necessary to find an effective and low-cost solution requiring a short calculation time, making it possible to define whether there is deception or not and to detect the deceived or erroneous or faulty sources in order not to use these said sources emitting false signals.

[0009] It is very important to find a solution that is economically acceptable for implementation on civil and military aircraft. It is necessary not to modify the satellite systems that exist today, given the enormous cost of existing geolocation satellite constellations.

[0010] Several technologies for protection against decoying currently exist. We can cite the encryption of signals which requires encryption of the signals emitted, and which is therefore reserved for certain military aircraft and therefore not generalizable to all civil aircraft.

[0011] Others have proposed measuring the power of the emitted signals, which is generally greater for decoys than for normal signals, which are generally weak signals, but this solution does not allow the detection of low-power decoy signals.

[0012] Some have proposed averaging the positions resulting from a large number of satellites in order to minimize the impact of one or more decoy satellites. This solution does not correct the situation, does not designate the decoy satellites and introduces an error into the results.

[0013] Sensor fusion can also be mentioned. By combining data from different sensors, such as inertial sensors, cameras or base stations, with GNSS signals, it is possible to detect decoy signals. Sensor fusion makes it possible to compare measurements from different sources and detect inconsistencies. These solutions require the availability of other sources of information such as laser inertial measurement units, which are heavy and expensive and which drift over time.

[0014] Researchers are working on developing advanced techniques to counter GNSS system deception. This includes the use of adaptive filters and multi-antenna localization methods. Multi-antenna systems require multiplying the number of antennas and therefore significantly increasing the cost, mass, and power consumption of the system. It also increases the difficulty of integrating antennas on the external skin of the aircraft.

[0015] The main object of the present invention is to define a device and a method making it possible to solve the problems stated above requiring a very short calculation time and this at low cost and mass.

[0016] For an aircraft it is extremely important not to make it heavier, nor to increase the manufacturing and maintenance costs. It is therefore fundamental to obtain the piloting information useful for flight control but with minimal mass and minimal cost.

[0017] For an aircraft pilot and for aircraft systems, it is essential to minimize the cost of ownership, the mass, the electrical consumption of the system while significantly improving reliability.

[0018] In the description below the terms mentioned will have the following definition:

[0019] - GNSS system: A GNSS system (for Global Navigation Satellite System) is a set mainly comprising an antenna and a receiver adapted to be able to receive data from several satellites. It mainly comprises- payment for one or more geolocation satellite galaxies and for each user, at least one GNSS antenna and one GNSS receiver.

[0020] - geolocation satellite: Geolocation satellites are satellites ar Earth-orbiting devices that provide precise positioning information and navigation services to users on the planet's surface and in Earth's atmosphere and to low-orbit satellites.

[0021] Their main function is to broadcast radio signals containing precise timing information and positioning data. GNSS receivers, such as GPS systems, use these signals to mainly calculate their position and speed with high accuracy.

[0022] The Global Positioning System (GPS), developed and operated by the United States government, is the best-known and most widely used geolocation system. It consists of a network of medium-earth orbit (MEO) satellites that provide global coverage. Other GNSS systems include GLONASS (Russia), Galileo (European Union), BeiDou (China), and NavIC (India), which also provide global or regional geolocation services.

[0023] - geocentric Cartesian coordinate system: A geocentric Cartesian coordinate system is a coordinate system of Three-dimensional coordinate system used to describe the position of objects or points in space with reference to the center of the Earth. It is a geocentric coordinate system fixed relative to the Earth rather than to an external reference point such as a geographic landmark.

[0024] In the geocentric Cartesian frame, coordinates are expressed in terms of distance from the center of the Earth. The central reference point is usually defined at the center of mass of the Earth, usually near the geometric center of the planet.

[0025] Geocentric Cartesian coordinates are generally defined using three orthogonal axes: X, Y, and Z. The Z axis is aligned with the Earth's rotational axis, pointing toward the geographic north pole. The X axis points to the intersection of the equator and the reference meridian (usually the Greenwich Meridian), while the Y axis is perpendicular to the X and Z axes, forming a straight coordinate system.

[0026] Geocentric Cartesian coordinates allow us to accurately describe the position of an object in three-dimensional space relative to the center of the Earth. These coordinates are widely used in fields such as geodesy, cartography, geophysics, astronomy, and satellite navigation systems. As a unit of length, we will choose the meter. - coincident points:

[0027] Two points coincide or are said to be coincident if the distance between these two points in space is less than or equal to a predefined distance D (for example 1 meter or one decimeter or 1 centimeter).

[0028] A set of points coincide or are said to be coincident if all the distances of the pairs of points in this set are less than a predefined distance D. - distant points:

[0029] Two points are said to be distant from each other if the distance between these two points in space is greater than a predefined distance D (for example 1 meter or one decimeter or 1 centimeter).

[0030] Two sets of points are said to be distant if all the distances of the pairs of points each taken in a set of different points are greater than a predefined distance D.

[0031] - aircraft: any flying object such as airplanes, helicopters or drones for example

[0032] - pair of points or doublet: set of two points

[0033] - triplet of points: set (m) of three points selected from n points with m=n! / (3!(n-3)!), the value of which is represented as an example, for n between 4 and 11, in the following table 1:

[0034] [Tables 1] Number of selected satellites: n Number of satellite triplets: m 4 4 5 10 6 20 7 35 8 56 9 84 10 120 11 165

[0035] - quadruplet of points or quartet: set of four points

[0036] - real-time calculations: calculations carried out in a very short time, less than a fraction of a second.

[0037] - precise time of emission (HE): for a geolocation satellite, the time transmission of a data train is based on a regularly reset atomic clock lately and which is accurate to within a few nanoseconds.

[0038] - satellites visible by an antenna: these are the satellites whose information transmitted by electromagnetic waves can be received by this antenna and interpreted by the receiver.

[0039] [Fig.l] schematically represents a possibility of algorithm according to the method concept set out in the present patent.

[0040] It is important to note that when we know the coordinates (XI, Y1, Z1, X2, Y2, Z2, X3, Y3, Z3) respectively, of the position of three satellites S1, S2, and S3, visible from a point P where the antenna of a GNSS receiver is located, as well as the precise distances dl, d2, d3, existing respectively between these said satellites and the antenna of the GNSS receiver, it is possible to calculate the three coordinates (x, y, and z,) of the antenna by solving the system of three equations with three unknowns of the form: [0041 ] d 12=(X 1 -x)2+(Y 1 -y )2+(Z 1 -z)2

[0042] d22=(X2-x)2+(Y2-y)2+(Z2-z)2

[0043] d32=(X3-x)2+(Y3-y)2+(Z3-z)2

[0044] In general, the resolution of this system of three equations with three unknowns gives two solutions located symmetrically with respect to the plane passing through the three satellites. It is therefore easy to eliminate the aberrant solution, for example by considering the distance between the antenna and the center of the Earth. For aircraft, the solution that interests us is necessarily found on the surface of the Earth or in the Earth's atmosphere.

[0045] It is important to note that this system of equations, although being a system of second degree equations, is quasi-linear and therefore can be solved with relatively low computing power, each unknown (x, y, and z) being able to be expressed directly without iterative calculation from the known parameters XI, Yl, Zl, X2, Y2, Z2, X3, Y3, Z3, dl, d2, and d3. <h2 style=";text-align:left;direction:ltr">

[0046] When using the intersection points xl, yl, zl,<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr">

[0047] [Tableaux2]<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> cl 2*(D3-A3) - (2*(G3-A3)*(E3-B3) / (H3-B3)) c2 2*(F3-C3) - ((2*(I3-C3)*(E3-B3)) / (H3-B3)) c3 (J3A2-K3A2) + (D3A2-A3A2) + (E3A2-B3A2) + (F3A2-C3A2) - (((J3a2-L3a2)*(E3-B3)) / (H3-B3)) - (((G3a2-A3a2)+(H3a2-B3a2)+(I3a2-C3a2))*(E3-B3)) / (H3-B3)) c4 (J3A2-L3A2) / (2*H3-2*B3) + (((G3A2-A3A2)+(H3A2-B3A2)+(I3A2-C3A2)) / (2*H3-2*B3)) - ((G3-A3)*C8) / ((H3-B3)*A8) c5 (((G3-A3)*B8) / ((H3-B3)*A8)) - ((I3-C3) / (H3-B3)) c6 C8 / A8 c7 -B8 / A8 c8 G8A2 + E8A2 + 1 c9 2*(G8*F8 - A3*G8 + E8*D8 - B3*E8 -C3 ) clO J3A2 - (A3A2 + B3A2 + C3A2) - (F8A2 + D8A2 - 2*A3*F8 - 2*B3*D8) xl F8+G8*B14 yi D8 + E8*B14 zl (-18+ SQRT((I8A2 + 4*H8*J8))) / (2*H8) x2 F8+G8*B18 y2 D8 + E8*B18 z2 (-18 - SQRT((I8A2 + 4*H8*J8))) / (2*H8)<h2 style=";text-align:left;direction:ltr">

[0048] We can then choose the point P by selecting the point PI with coordinates (xl,yl,zl) or the point P2 with coordinates (x2,y2,z2) depending on the distance of these points PI and P2 from the center of the earth in order to check which is on the surface of the earth or in the atmosphere.

[0049] We therefore see that it is possible, with simple and non-iterative calculations, to find the coordinates (x, y, and z) of a point P in the atmosphere or on the surface of the earth if we know precisely the coordinates of three satellites and the precise distances existing between these said satellites and the point P.

[0050] Unfortunately this system of three equations with three unknowns cannot be used to calculate the precise position of the antenna. Indeed, to calculate the distance separating the satellite from the antenna, it is necessary to know both the precise time of transmission and the precise time of reception, as well as the precise speed of light which is of the order of 2.99.108 m / s. The precise time of emission is known because the satellites have atomic clocks accurate to within a few nanoseconds. On the other hand, the time of reception is not known precisely (known only to within a few microseconds) because the receivers do not generally have atomic clocks. The measurement of the time of reception has an offset (a bias) which makes the knowledge of the distance between the satellite and point P too imprecise for most applications. Today, to have a measurement of the position of the antenna, it is therefore imperative to consider a fourth satellite and to solve the system of four non-linear equations with four unknowns which are the three coordinates x, y, z, of the antenna and the bias of the measurement of the time of reception of the antenna, which is substantially the same for all the signals arriving at substantially the same time and captured by the antenna.This system of 4 equations with four unknowns is highly nonlinear and requires a lot of computing power. It is therefore practically impossible to perform many iterative calculations integrating such a system of nonlinear equations in the short time required to have a real-time calculation.

[0051] The main idea presented in this invention patent is to use the system of three equations with three unknowns in order to calculate the coordinates of the points corresponding to all the satellite triplets that are part of the set of selected satellites and although these coordinates are far from the correct values ​​of the antenna position, and although the chosen value of the speed of light is a predetermined value (for example 2.99x108 m / s, which is not an exact value), the resulting points P can be grouped into point clouds depending on whether these points are coincident or not.The analysis of the coincidence of these point clouds, as a function of the number of satellites selected, the number of point clouds and the knowledge of the satellites having contributed to the creation of the points contained in each point cloud makes it possible, following the application of a function or a decision table, or an algorithm, the main subject of this patent, to determine whether such or such satellite is a decoy or malfunctioning satellite.

[0052] It is then possible to choose 4 non-decoy and correctly functioning satellites to calculate in a conventional manner the precise position of the antenna and the clock bias by solving the system of 4 equations with 4 unknowns from 4 or more non-decoy satellites.

[0053] The main objectives of the invention proposed here make it possible to solve the problems proposed previously and to propose a precise and reliable geolocation system by eliminating the sources of deception, even multiple, at low cost, without modifying the galaxies of existing geolocation satellites, with low calculation time allowing a short refresh of the calculations, and therefore to obtain information in real time.

[0054] It combats the universally recognized idea that it is necessary to compare the coordinates of a point obtained with other independent systems or to compare the arrival phases of the carrier waves, or to measure the power of the waves, to deduce whether there is deception or not. These so-called current methods do not allow for the precise and reliable determination of either the sources of deception or the decoy satellites, in particular by considering only four satellites.

[0055] The invention succeeds in solving the problems stated above by proposing a satellite geolocation device making it possible to calculate the position of a point P of an aircraft, in real time, with great precision and this even in the presence of one or more decoy emissions or emissions coming from malfunctioning satellites, this system comprising:

[0056] - a set of n satellites (with n being at least equal to 4) of geolocation ap belonging to one or more galaxies of geolocation satellites such as those of the GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), BEUDOU (Navigation Satellite System), GALILEO (European Positioning System), NavIC or IRNSS (Indian Regional Navigation Satellite System) systems, these so-called geolocation satellites regularly transmitting several data, the main ones being: the name of the satellite, its position in space (or the means for calculating its precise position in space), and the precise time of transmission HE,

[0057] - a GNSS antenna called ANT placed on a point P of the aircraft,

[0058] - a receiver connected to the ANT antenna, and capable of receiving the data transmitted by the geolocation satellites and in particular for each satellite the name of the satellite, its position in space (or the means enabling its precise position in space to be calculated), and the exact time of transmission HE of said data received by the ANT antenna,

[0059] - a means of selecting n satellites called SI,..., Sn, chosen from the sa tellites visible by the ANT antenna, each selected satellite transmitting its name, the exact time of transmission HE of the messages, called respectively HE1, ..., HEn, and the coordinates respectively of its position (or the means of calculating the exact position of each satellite) called XI, Yl, Zl, ..., Xn, Yn, Zn,

[0060] - said receiver comprising means for measuring the approximate time of reception on the antenna ANT, called respectively HR1, ..., HRn, of the signals sent by each selected satellite SI, ..., Sn,

[0061] - a means of calculating the approximate distances dl, ..., dn using respec tively the time difference between the precise emission time HE1, .. .,HEn and the approximate reception time HR1,..., HRn and using for the speed c of propagation of the electromagnetic wave a predetermined value c for example 2.99.108 meters per second, according to the following formulas:

[0062] dl=c*(HRl-HEl)

[0063] .......

[0064] dn=c*(HRn-HEn)

[0065] - a means for grouping the n selected satellites SI,..Sn into m triplets of satellites Tl, ..., Tm, m being an integer greater than or equal to 4 and a function of n such that m=n! / (3!(n-3)!),

[0066] - a means of calculation, for each of the m triplets of satellites comprising the 3 sa tellites Sr, Ss, and St, comprising respectively for each satellite the time of emission HEr, HEs, HEt, each satellite having as coordinates respectively Xr, Yr, Zr, Xs, Ys, Zs, and Xt, Yt, Zt, and from the approximate time of reception of the signals on the antenna HRr, HRs, HRt, (r, s, and t being three different integers between 1 and n), making it possible to define the coordinates of a point called pi, (i being between 1 and m), each point pi having respectively as spatial coordinates xi, yi, zi, each coordinate xi, yi, zi being the result of the resolution of the following system called here function Fl

[0067] c2*(HRr-HEr)2=(Xr-xi)2+(Yr-yi)2+(Zr-zi)2

[0068] c2*(HRs-HEs)2=(Xs-xi)2+(Ys-yi)2+(Zs-zi)2

[0069] c2*(HRt-HEt)2=(Xt-xi)2+(Yt-yi)2+(Zt-zi)2

[0070] and eliminating the aberrant solution,

[0071] each of the m points pi being named prst where r, s and t are the numbers of the satellites Sr, Ss and St, for example the point pl23 is the point coming from the resolution of the system of the three previous equations considering the satellites SI, S2, and S3 and the distances cl, c2, and c3, and for example the point p 124 is the point coming from the resolution of the system of the three previous equations considering the satellites SI, S2, and S4 and the distances cl, c2, and c4,

[0072] - a means of grouping coincident pi points and non-coincident pi points coincident, by calculating two by two the distances between the points pi and by determining respectively the distances less than or equal to a predetermined distance D and those greater than this said distance D,

[0073] - a means of selecting the decoy satellite(s) and / or not functioning correctly correctly from the nature of the non-coincident pi points, and the non-decoyed satellites, and / or functioning correctly from the nature of the coincident pi points,

[0074] - a means of calculating the precise position of point P using 4 selected satellites among the undecoyed satellites and using a system of 4 equations with four unknowns which are the three spatial coordinates of point P and the error (or bias) of measurement of the time of reception of the signals, and / or by averaging the values ​​of coordinates found by taking into account several quadruplets of undecoyed satellites.

[0075] It is advantageous that the means for selecting the decoy satellite(s) and / or satellite(s) not functioning correctly comprises all the satellites which have not generated a point cloud comprising at least four coincident pi points.

[0076] It is advantageous that the number n of selected satellites (S1, S2, S3, S4) is equal to 4, the number m of satellite triplets being equal to 4, and the points generated by the four satellite triplets being called pl23, pl24, pl34, p234, these said points being obtained respectively by the function Fl, the determination of the good functioning or the bad functioning (for example of the decoy) being obtained in accordance with the following logic:

[0077] - if a single point cloud groups together all four points pi, that is to say if the four points pl23, pl34, p234 and pl24 are coincident, we can deduce that the four selected satellites SI, S2, S3, and S4 are not decoyed and are functioning correctly,

[0078] - if at least one point pi is not coincident with the 3 other points pi, we can deduce that at least one satellite is decoyed or not functioning properly.

[0079] It is advantageous that the number n of selected satellites (S1, S2, S3, S4, S5) is equal to 5, the number m of satellite triplets being equal to 10, and the means of selecting the decoy satellite(s) and / or not functioning correctly is determined as follows:

[0080] - if the 10 points pl23, pl24, pl25, pl34, pl35, pl45, p234, p235, pl45 and p345 are coincident, we can deduce that the five selected satellites are not decoyed and are functioning correctly,

[0081] - if among the ten points pl23, pl24, pl25, pl34, pl35, pl45, p234, p235, pl45 and p345 only four are coincident, then the four satellites being at the origin of these said four points are not decoyed and functioning correctly, for example if points p 123, p 124, pl34, and p234 are coincident then satellites SI, S2, S3, S4 are not decoyed and functioning correctly, satellite S5 being the decoy satellite or not functioning correctly,

[0082] - if among the ten points pl23, pl24, pl25, pl34, pl35, pl45, p234, p235, pl45 and p345 only three or less than three are coincident, we can conclude that at least two satellites are decoy or not functioning properly.

[0083] Advantageous method of satellite geolocation using the device described above and comprising the following steps taken in this order or in a different order at each calculation step:

[0084] - Step 1: the value of n is initially chosen equal to 3

[0085] - Step 2: n=n+l

[0086] - Step 3: selection of n geolocation satellites SI, ..Sn visible from the antenna and whose signals are sufficiently strong,

[0087] - Step 4: collection of data from these n satellites respectively their name (SI, ... , Sn), their position having as coordinates respectively (XI, Yl, Zl,....., Xn, Yn, Zn), and the precise time of emission (respectively HE1, ...., HEn), as well as the approximate time of arrival of the signals on the antenna (HR1, ...., HRn) emitted by these said n satellites,

[0088] - Step 5: we calculate the approximate distances dl, .... , dn existing between the n sa tellites and point P taking the speed of light c equal to a value between 2.95x108 meters per second and 3.05x108 meters per second, for example 2.99x108 meters per second using the following formulas:

[0089] dl=c*(HRl-HEl)

[0090] .......

[0091] dn=c*(HRn-HEn)

[0092] - Step 6:

[0093] Considering all the triplets (Tl,..., Tm) of the satellites (SI, ..., Sn), we solve the following m systems of three equations with three unknowns using the function Fl in order to obtain the three coordinates (xpl, ypl, zpl, ...., xpm, ypm, zpm) of the m points pl, ..., pm:

[0094] dp 12=(X 1 -xp 1 )2+(Y 1 -yp 1 )2+(Z 1 -zp 1 )2

[0095] dp22=(X2-xp 1 )2+(Y2-yp 1 )2+(Z2-zp 1 )2

[0096] dp32=(X3-xpl)2+(Y3-ypl)2+(Z3-zpl)2

[0097] .................................

[0098] dpl2=(Xm-2-xpm)2+(Y m-2-ypm)2+(Z m-2-zpm)2

[0099] dp22=(Xm-1 -xpm)2+(Y m-1 -ypm)2+(Z m-1 -zpm)2

[0100] dp32=(Xm-xpm)2+(Y m-ypm)2+(Zm-zpm)2

[0101] - Step 7: the following check is carried out:

[0102] a) if among the m points pl, ..., pm obtained, at least four points are coincident, we can conclude that the satellites having generated the coincident points are not deceived and are functioning correctly. We can then carry out Step 8

[0103] b) if among the m points pl, ..., pm obtained, there are not at least four coincident points, we can conclude that at least n-3 satellites are decoyed and / or are not functioning correctly. It is then necessary to return to step 2.

[0104] - Step 8:

[0105] The position of point P can then be calculated from the coordinates of the undeceived and correctly functioning satellites, in a conventional manner by solving the system of four unknowns making it possible to obtain the values ​​of the three coordinates of point P and of the bias t corresponding to the measurement error of the reception time of the receiver.

[0106] A preferred embodiment according to the invention is described below. This description uses [Fig.l].

[0107] Device comprising

[0108] - a set of n satellites (with n being at least equal to 4) of geolocation ap belonging to one or more galaxies of geolocation satellites such as those of the GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), BEUDOU (Navigation Satellite System), GALILEO (European Positioning System), NavIC or IRNSS (Indian Regional Navigation Satellite System) systems, these so-called geolocation satellites regularly transmitting several data, the main ones being: the name of the satellite, its position in space (or the means for calculating its precise position in space), and the precise time of transmission HE,

[0109] - a GNSS antenna called ANT placed on a point P of the aircraft,

[0110] - a receiver connected to the ANT antenna, and capable of receiving the data transmitted by the geolocation satellites and in particular for each satellite the name of the satellite, its position in space (or the means enabling its precise position in space to be calculated), and the exact time of transmission HE of said data received by the ANT antenna,

[0111] - a means of selecting n satellites called SI Sn, chosen from the sa tellites visible by the ANT antenna, each selected satellite transmitting its name, the exact time of transmission HE of the messages, called respectively HE1, ..., HEn, and the coordinates respectively of its position (or the means of calculating the exact position of each satellite) called XI, Yl, Zl, ..., Xn, Yn, Zn,

[0112] - said receiver comprising means for measuring the approximate time of reception on the antenna ANT, called respectively HR1, ..., HRn, of the signals sent by each selected satellite SI, ..., Sn,

[0113] - a means of calculating the approximate distances dl, ..., dn using respec tively the time difference between the precise emission time HE1, .. .,HEn and the approximate reception time HR1,..., HRn and using for the speed c of propagation of the electromagnetic wave a predetermined value c for example 2.99.108 meters per second, according to the following formulas:

[0114] dl=c*(HRl-HEl)

[0115] .......

[0116] dn=c*(HRn-HEn)

[0117] - a means for grouping the n selected satellites SI,..., Sn into m triplets of satellites Tl, ..., Tm, m being an integer greater than or equal to 4 and a function of n such that m=n! / (3!(n-3)!),

[0118] - a means of calculation, for each of the m triplets of satellites comprising the 3 sa tellites Sr, Ss, and St, comprising respectively for each satellite the time of emission HEr, HEs, HEt, each satellite having as coordinates respectively Xr, Yr, Zr, Xs, Ys, Zs, and Xt, Yt, Zt, and from the approximate time of reception of the signals on the antenna HRr, HRs, HRt, (r, s, and t being three different integers between 1 and n), making it possible to define the coordinates of a point called pi, (i being between 1 and m), each point pi having respectively as spatial coordinates xi, yi, zi, each coordinate xi, yi, zi being the result of the resolution of the following system called here function Fl

[0119] c2*(HRr-HEr)2=(Xr-xi)2+(Yr-yi)2+(Zr-zi)2

[0120] c2*(HRs-HEs)2=(Xs-xi)2+(Ys-yi)2+(Zs-zi)2

[0121] c2*(HRt-HEt)2=(Xt-xi)2+(Yt-yi)2+(Zt-zi)2

[0122] and eliminating the aberrant solution,

[0123] each of the m points pi being named prst where r, s and t are the numbers of the satellites Sr, Ss and St, for example the point pl23 is the point coming from the resolution of the system of the three previous equations considering the satellites SI, S2, and S3 and the distances cl, c2, and c3, and for example the point p 124 is the point coming from the resolution of the system of the three previous equations considering the satellites SI, S2, and S4 and the distances cl, c2, and c4,

[0124] - a means of grouping coincident pi points and non-coincident pi points coincident, by calculating two by two the distances between the points pi and by determining respectively the distances less than or equal to a predetermined distance D and those greater than this said distance D,

[0125] - a means of selecting the decoy satellite(s) and / or not functioning correctly correctly from the nature of the non-coincident pi points, and the non-decoyed satellites, and / or functioning correctly from the nature of the coincident pi points,

[0126] - a means of calculating the precise position of the point P using 4 chosen satellites among the undecoyed satellites and using a system of 4 equations with four unknowns which are the three spatial coordinates of point P and the error (or bias) of measurement of the time of reception of the signals, and / or by averaging the coordinate values ​​found by taking into account several quadruplets of undecoyed satellites,

[0127] And following the following steps:

[0128] - Step 1: the value of n is initially chosen equal to 3

[0129] - Step 2: n=n+l

[0130] - Step 3: selection of n geolocation satellites SI, Sn visible from the antenna and whose signals are sufficiently strong,

[0131] - Step 4: collection of data from these n satellites respectively their name (SI, ... ,Sn), their position having as coordinates respectively (XI, Yl, Zl,....., Xn, Yn, Zn), and the precise time of emission (respectively HE1, HEn), as well as the approximate time of arrival of the signals on the antenna (HR1, HRn) emitted by these said n satellites,

[0132] - Step 5: we calculate the approximate distances dl, .... , dn existing between the n sa tellites and point P taking the speed of light c equal to a value between 2.95x108 meters per second and 3.05x108 meters per second, for example 2.99x108 meters per second using the following formulas:

[0133] dl=c*(HRl-HEl)

[0134] .......

[0135] dn=c*(HRn-HEn)

[0136] - Step 6:

[0137] Considering all the triplets (Tl,..., Tm) of the satellites (SI, ..., Sn), we solve the following m systems of three equations with three unknowns using the function Fl in order to obtain the three coordinates (xpl, ypl, zpl, ...., xpm, ypm, zpm) of the m points pl, ..., pm:

[0138] dp 12=(X 1 -xp 1 )2+(Y 1 -yp 1 )2+(Z 1 -zp 1 )2

[0139] dp22=(X2-xp 1)2+(Y2-yp 1)2+(Z2-zp 1)2

[0140] dp32=(X3-xp 1)2+(Y3-yp 1)2+(Z3-zp 1)2

[0141] .................................

[0142] dpl2=(Xm-2-xpm)2+(Y m-2-ypm)2+(Z m-2-zpm)2

[0143] dp22=(Xm-l-xpm)2+(Y ml-ypm)2+(Z ml-zpm)2

[0144] dp32=(Xm-xpm)2+(Y m-ypm)2+(Zm-zpm)2

[0145] - Step 7: the following check is carried out:

[0146] a) if among the m points pl, ..., pm obtained, at least four points are coincident, we can conclude that the satellites having generated the coincident points are not deceived and are functioning correctly. We can then carry out Step 8

[0147] b) if among the m points pl, ..., pm obtained, there are not at least four coincident points, we can conclude that at least n-3 satellites are decoyed and / or are not functioning correctly. It is then necessary to return to step 2.

[0148] - Step 8:

[0149] The position of point P can then be calculated from the coordinates of the undeceived and correctly functioning satellites, in a conventional manner by solving the system of four unknowns making it possible to obtain the values ​​of the three coordinates of point P and of the bias t corresponding to the measurement error of the reception time of the receiver.

[0150] High-precision analyses and calculations were carried out and made it possible to verify the relevance and precision of the device and method which are the subject of this patent.

[0151] Actual tests were carried out and made it possible to verify the relevance and precision of the device and method which are the subject of this patent.

[0152] Those skilled in the art will be able to apply this concept to many other similar systems without departing from the scope of the invention defined in the attached claims and in particular for applications other than aeronautical applications such as systems mounted on land or nautical vehicles or even on fixed installations.

Claims

Claims

1. Satellite geolocation device for calculating the position of a point (P) of an aircraft, in real time, with great precision and this even in the presence of one or more decoy emissions or emissions coming from malfunctioning satellites, this system comprising: - a set of (n) geolocation satellites (with n being at least equal to four) belonging to one or more galaxies of geolocation satellites such as those of the GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), BEUDOU (Navigation Satellite System), GALILEO (European Positioning System), NavIC or IRNSS (Indian Regional Navigation Satellite System) systems, these so-called geolocation satellites regularly transmitting several data, the main ones being: the name of the satellite, its position in space (or the means for calculating its precise position in space), and the precise time of transmission HE, - a GNSS antenna called (ANT) placed on the point (P) of the aircraft, - a receiver connected to the antenna (ANT), and capable of receiving the data transmitted by the geolocation satellites and in particular for each satellite the name of the satellite, its position in space (or the means for calculating its precise position in space), and the exact time of transmission (HE) of said data received by the antenna (ANT), - a means for selecting n satellites called (SI)(Sn), chosen from among the satellites visible by the antenna (ANT), each selected satellite transmitting its name, the exact time of transmission (HE) of the messages, called respectively (HE1), ..., (HEn), and the coordinates respectively of its position (or the means for calculating the exact position of each satellite) called (XI), (Yl), (Zl), ..., (Xn), (Yn), (Zn), - said receiver comprising a means for measuring the approximate time of reception on the antenna (ANT), called respectively (HR1), ..., (HRn), of the signals sent by each selected satellite (SI), ..., (Sn), - a means of calculating approximate distances (dl), ..., (dn) using respectively the time difference between the precise transmission time (HE1), .. .,(HEn) and the reception time ap- approximate (HR1),..., (HRn) and using for the speed (c) of propagation of the electromagnetic wave a predetermined value (c) for example 2.99.108 meters per second, according to the following formulas: dl=c*(HRl-HEl) dn=c*(HRn-HEn) - a means of grouping the n selected satellites (SI),..., (Sn) into m satellite triplets (Tl),..., (Tm), m being an integer greater than or equal to 4 and a function of n such that m=n! / (3!(n-3)!), - a calculation means, for each of the m satellite triplets comprising the 3 satellites (Sr), (Ss), and (St), comprising respectively for each satellite the time of emission (Her), (HEs), (Het), each satellite having as coordinates respectively (Xr), (Yr), (Zr), (Xs), (Ys), (Zs), and (Xt), (Yt), (Zt), and from the approximate time of reception of the signals on the antenna (HRr), (HRs), (HRt), (r, s, and t being three different integers between 1 and n), making it possible to define the coordinates of a point called (pi), (i being between 1 and m), each point (pi) having respectively as spatial coordinates (xi), (yi), (zi), each coordinate (xi), (yi),(zi) being the result of the resolution of the following system called here function (Fl) c2*(HRr-HEr)2=(Xr-xi)2+(Yr-yi)2+(Zr-zi)2 c2*(HRs-HEs)2=(Xs-xi)2+(Ys-yi)2+(Zs-zi)2 c2*(HRt-HEt)2=(Xt-xi)2+(Yt-yi)2+(Zt-zi)2 and eliminating the aberrant solution, each of the m points (pi) being named (prst) where r, s and t are the numbers of the satellites (Sr), (Ss) and (St), for example the point (pl23) is the point coming from the resolution of the system of the three previous equations considering the satellites (SI), (S2), and (S3) and the distances (cl), (c2), and (c3), and for example the point (pl24) is the point coming from the resolution of the system of the three previous equations considering the satellites (SI), (S2), and (S4) and the distances (cl), (c2), and (c4), - a means of grouping coincident points (pi) and non-coincident points (pi), by calculating two by two the distances between the points (pi) and determining respectively the distances less than or equal to a predetermined distance (D) and those greater than this said distance (D), - a means of selecting the decoy satellite(s) and / or not functioning correctly based on the nature of the points (pi) not coincident, and undecoyed satellites, and / or functioning correctly from the nature of the coincident points (pi), - a means of calculating the precise position of the point (P) using 4 satellites chosen from the undecoyed satellites and using a system of 4 equations with four unknowns which are the three spatial coordinates of the point (P) and the error (or bias) of measurement of the time of reception of the signals, and / or by averaging the coordinate values ​​found by taking into account several quadruplets of undecoyed satellites.

2. Device according to claim 1 characterized in that the means for selecting the decoy satellite(s) and / or satellite(s) not functioning correctly comprises all the satellites which have not generated a point cloud comprising at least four coincident points (pi).

3. Device according to claim 1 characterized in that the number n of selected satellites (S1, S2, S3, S4) is equal to 4, the number m of satellite triplets being equal to 4, and the points generated by the four satellite triplets being called (pl23), (pl24), (pl34), (p234), these said points being obtained respectively by the function (Fl), the determination of the correct operation or the incorrect operation (for example of deception) being obtained in accordance with the following logic: - if a single cloud of points groups together all four points (pi), that is to say if the four points (pl23), (pl34), (p234) and (pl24) are coincident, it can be deduced that the four selected satellites (SI), (S2), (S3), and (S4) are not decoyed and are functioning correctly, - if at least one point (pi) is not coincident with the other 3 points (pi), we can deduce that at least one satellite is decoyed or not functioning properly.

4. Device according to claim 1 characterized in that the number n of selected satellites (S1, S2, S3, S4, S5) is equal to 5, the number m of satellite triplets being equal to 10, and the means for selecting the decoy satellite(s) and / or not functioning correctly is determined in the following manner: - if the 10 points (pl23), (pl24), (pl25), (pl34), (pl35), (pl45), (p234), (p235), (pl45) and (p345) are coincident, it can be deduced that the five selected satellites are not decoyed and functioning correctly, - if among the ten points (pl23), (pl24), (pl25), (pl34), (pl35), (pl45), (p234), (p235), (pl45) and (p345) only four are coincident, then the four satellites being at the origin of these said four points are not decoyed and functioning correctly, for example if the points (pl23), (pl24), (pl34), and (p23)4 are coincident then the satellites (SI), (S2), (S3), (S4) are not decoyed and functioning correctly, the satellite (S5) being the decoy satellite or not functioning correctly, - if among the ten points (pl23), (pl24), (pl25), (pl34), (pl35), (pl45), (p234), (p235), (pl45) and (p345) only three or less than three are coincident, we can conclude that at least two satellites are decoyed or not functioning correctly.

5. A method of satellite geolocation using the device of claim 1 and comprising the following steps taken in this order or in a different order at each calculation step: - Step 1: the value of n is initially chosen to be equal to 3 - Step 2: n=n+l - Step 3: selection of n geolocation satellites (SI), (Sn) visible from the antenna and whose signals are sufficiently strong, - Step 4: collection of data from these n satellites respectively their name (SI, ..., Sn), their position having as coordinates respectively (XI, Yl, Zl,....., Xn, Yn, Zn), and the precise time of emission respectively (HE1, ...., HEn), as well as the approximate time of arrival of the signals on the antenna (HR1, ...., HRn) emitted by these said n satellites, - Step 5: we calculate the approximate distances (dl), ...., (dn) existing between the n satellites and the point (P) by taking the speed of light (c) equal to a value between 2.95x108 meters per second and 3.05x108 meters per second, for example 2.99x108 meters per second by following the following formulas: dl=c*(HRl-HEl) dn=c*(HRn-HEn) - Step 6: Considering all the triplets (Tl,..., Tm) of the satellites (SI, ..., Sn), we solve the following m systems of three equations with three unknowns using the function Fl in order to obtain the three coordinates (xpl, ypl, zpl, ...., xpm, ypm, zpm) of the mpoints pl, ..., pm: dp 12=(X 1 -xp 1 )2+( Y1 -yp 1 )2+(Z 1 -zp 1 )2 dp22=(X2-xp 1 )2+( Y2-yp 1 )2+(Z2-zp 1 )2 dp32=(X3-xpl)2+(Y3-ypl)2+(Z3-zpl)2 dpl2=(Xm-2-xpm)2+(Y m-2-ypm)2+(Z m-2-zpm)2 dp22=(Xm-l-xpm)2+(Y ml-ypm)2+(Z ml-zpm)2 dp32=(Xm-xpm)2+(Ym-ypm)2+(Zm-zpm)2 - Step 7: we carry out the following check: a) if among the m points (pl), ..(pm) obtained, at least four points are coincident, we can conclude that the satellites having generated the coincident points are not deceived and are functioning correctly. We can then carry out Step 8 b) if among the m points (pl), ..., ( pm) obtained, there are not at least four coincident points, we can conclude that at least n-3 satellites are decoyed and / or are not functioning correctly. It is then necessary to return to step 2. - Step 8: The position of the point (P) can then be calculated from the coordinates of the undeceived and correctly functioning satellites, in a conventional manner by solving the system of four unknowns allowing the values ​​of the three coordinates of the point (P) and the bias (t) corresponding to the measurement error of the reception time of the receiver to be obtained.

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