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

Abstract

TITLE: Anti-spoofing device and method for aircraft using data analysis from geolocation satellite triplets. Satellite geolocation device and method enabling the calculation of the position of a point P on an aircraft, in real time, with high accuracy, even in the presence of one or more spoofed emissions or emissions from malfunctioning satellites, by analyzing data provided by a set of geolocation satellite triplets and based on the coincidence or non-coincidence of the points obtained from these satellite triplets. Figure for the abstract: Fig. 1

Description

Title of the invention: Device and method for aircraft anti-deception by analyzing data from geolocation satellite triplets.

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

[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 the decoy satellites among the geolocation satellite constellations.

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

[0006] The invention finds particular utility in the aeronautical field, where knowledge of position-related parameters is fundamental and where the reliability of this information must be exceptionally high. The possibilities for spoofing currently make existing geolocation technologies, particularly for civil aircraft, unattractive given the potential risks of spoofing, and in fact reduce the overall reliability of this technology to a level that renders it unacceptable for so-called critical applications.

[0007] Spoofing GNSS (Global Navigation Satellite Systems) 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 little computation time, allowing us to determine whether there is deception or not and to detect deceived, erroneous or faulty sources in order to avoid using these sources emitting false signals.

[0009] It is very important to find a solution that is economically acceptable for implementation on both civil and military aircraft. It is necessary to avoid modifying existing satellite systems, given the exorbitant cost of existing geolocation satellite constellations.

[0010] Several technologies for protection against deception currently exist. One example is signal encryption, which requires encryption of the transmitted signals and is therefore reserved for certain military aircraft and thus not applicable 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 identify 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 spoofing signals. Sensor fusion makes it possible to compare measurements from different sources and detect inconsistencies. These solutions require access to other sources of information, such as laser inertial measurement units (LIMs), which are bulky, expensive, and subject to drift over time.

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

[0015] The main object of the present invention is to define a device and a method for solving the problems stated above, requiring very short computation time and at low cost and mass.

[0016] For an aircraft, it is extremely important not to increase its weight or the cost of manufacturing and maintenance. It is therefore essential to obtain the piloting information necessary for flight control, but with minimal mass and cost.

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

[0018] In the description below, the terms mentioned shall have the following definitions:

[0019] - GNSS system: A GNSS (Global Navigation Satellite System) is a set mainly comprising an antenna and a suitable receiver to be able to receive data from multiple satellites. It mainly comprises 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 artificial satellites in orbit around the earth that provide accurate positioning information and navigation services to users on the planet's surface and in the Earth's atmosphere and to satellites in low Earth orbit.

[0021] Their main function is to transmit radio signals containing precise timing information and positioning data. GNSS receivers, such as GPS systems, use these signals primarily to 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 satellites in medium Earth orbit (MEO) that provide global coverage. Other GNSS systems include GLONASS (Russia), Galileo (European Union), BeiDou (China), and NavIC (India), which also offer geolocation services on a global or regional scale.

[0023] - Geocentric Cartesian coordinate system: A geocentric Cartesian coordinate system is a coordinate system of Three-dimensional coordinates 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 with respect to the Earth rather than with respect to an external reference point such as a geographical benchmark.

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

[0025] Geocentric Cartesian coordinates are generally defined using three orthogonal axes: X, Y, and Z. The Z-axis is aligned with the Earth's axis of rotation, pointing towards the geographic North Pole. The X-axis points towards the point of 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 right-handed coordinate system.

[0026] Geocentric Cartesian coordinates allow for the precise description of an object's position in three-dimensional space relative to the Earth's center. These coordinates are widely used in fields such as geodesy, cartography, geophysics, astronomy, and satellite navigation systems. The meter will be used as the unit of length. - coincident points:

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

[0028] A set of points coincide or are said to coincide 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 1 decimeter or 1 centimeter).

[0030] Two sets of points are said to be distant if all the distances of pairs of points taken each in a different set of 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)!), whose value is shown as an example, for n between 4 and 11, in the following table 1:

[0034] [Tables 1] Number of selected tellites born: 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 performed in a very short time, less than one fraction of a second.

[0037] - precise time of transmission (ET): for a geolocation satellite, the time The transmission of a data train is based on an atomic clock that is regularly calibrated and accurate to within a few nanoseconds.

[0038] - satellites visible to 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. 1 schematically represents one possible algorithm according to the process concept stated in this patent.

[0040] It is important to note that when the coordinates (XI, Y1, Z1, X2, Y2, Z2, X3, Y3, Z3) of the position of three satellites S1, S2, and S3, visible from a point P where the antenna of a GNSS receiver is located, are known, as well as the precise distances d1, 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+( Y1 -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, solving this system of three equations with three unknowns yields two solutions located symmetrically with respect to the plane passing through the three satellites. It is therefore easy to eliminate the outlier, for example by considering the distance between the antenna and the center of the Earth. For aircraft, the solution of interest is necessarily located on the Earth's surface 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 almost 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.

[0046] When exposing the cordonnées xl, yl, zl, x2, y2 and z2 to the intersection points, using the intermediary calculations, on the table 2 “EXCEL” in the façon suivante:

[0047] [Tableaux2] 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)

[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 one is on the surface of the earth or in the atmosphere.

[0049] We can 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 between the satellite and 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 on the order of 2.99 x 10⁸ m / s. The precise time of transmission is known because satellites have atomic clocks accurate to within a few nanoseconds. However, the time of reception is not known precisely (known only to (within a few microseconds) because receivers generally do not have atomic clocks. The measurement of the reception time has a discrepancy (a bias) that makes the known distance between the satellite and point P too imprecise for most applications. Therefore, to obtain a measurement of the antenna's position, it is now essential to consider a fourth satellite and solve the system of four nonlinear equations with four unknowns: the three coordinates x, y, z of the antenna and the bias in the measurement of the antenna's reception time, which is essentially the same for all signals arriving at roughly the same instant and received by the antenna. This system of four equations with four unknowns is highly nonlinear and requires significant computing power.It is therefore practically impossible to perform numerous iterative calculations integrating such a system of nonlinear equations in the short time required for real-time computation.

[0051] The main idea presented in this patent of invention is to use the system of three equations with three unknowns in order to calculate the coordinates of the points corresponding to all the triplets of satellites 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 as follows 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 which contributed to the creation of the points contained in each point cloud, makes it possible, by applying a function or a decision table, or an algorithm, the main subject of this patent, to determine whether a given satellite is a decoy or malfunctioning satellite.

[0052] It is then possible to choose 4 satellites that are not deceived and are functioning correctly in order to calculate in a conventional way the precise position of the antenna and the clock bias by solving the system of 4 equations with 4 unknowns from 4 or more satellites that are not deceived.

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

[0054] It challenges the universally accepted 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 the measurement of the wave power, are used to determine whether or not there is spoofing. These current methods do not allow for the precise and reliable identification of either the sources of spoofing or the spoofing satellites, particularly when considering only four satellites.

[0055] The invention solves the problems stated above by proposing a satellite geolocation device that calculates the position of a point P of an aircraft in real time with high precision, even in the presence of one or more spoofed emissions or emissions from malfunctioning satellites. This system comprises:

[0056] - a set of n geolocation satellites (with n being at least equal to 4) belonging to one or more geolocation satellite galaxies 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 geolocation satellites regularly transmit several data, the main ones being: the name of the satellite, its position in space (or the means allowing its precise position in space to be calculated), and the precise time of transmission ET,

[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 of calculating its precise position in space), and the exact time of transmission HE of said data received by the ANT antenna,

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

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

[0061] - a means of calculating the approximate distances dl, ..., dn using respectively 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 x 10⁸ meters per second, according to the following formulas:

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

[0063] .......

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

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

[0066] - a calculation method, for each of the m satellite triplets comprising the 3 satellites Sr, Ss, and St, each with its respective transmission time HEr, HEs, and HEt, and each satellite having coordinates Xr, Yr, Zr, Xs, Ys, Zs, and Xt, Yt, Zt, respectively, and from the approximate time of signal reception on the antenna HRr, HRs, HRt (r, s, and t being three different integers between 1 and n), allow us to define the coordinates of a point called pi (i being between 1 and m). Each point pi has spatial coordinates xi, yi, and zi, respectively, each coordinate xi, yi, and zi being the result of solving the following system, here called the 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 by 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 resulting from the solution of the system of the three preceding equations considering the satellites SI, S2, and S3 and the distances cl,c2, and c3, and for example the point pl24 is the point resulting from the solution of the system of the three preceding 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 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 and / or non-functioning satellite(s) correctly based on the nature of non-coincident pi points, and undeceived satellites, and / or functioning correctly based on the nature of coincident pi points,

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

[0075] It is advantageous that the means for selecting the decoy and / or malfunctioning satellite(s) includes all satellites that 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 denoted pl23, pl24, pl34, p234, these said points being obtained respectively by the function Fl, the determination of proper functioning or improper functioning (for example, spoofing) being obtained in accordance with the following logic:

[0077] - if a single scatter plot groups all four points pi, that is to say if the Four points pl23, pl34, p234 and pl24 coincide; therefore, 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 other 3 points pi, we can deduce that at least one satellite is being deceived or is not functioning correctly.

[0079] It is advantageous that the number n of selected satellites (SI, 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 and / or malfunctioning satellite(s) is determined as follows:

[0080] - if the 10 points pl23, pl24, pl25, pl34, pl35, pl45, p234, p235, pl45 and p345 are Since the data coincide, we can deduce that the five selected satellites are not spoofed 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, so the four satellites at the origin of these four points are not decoyed and are functioning correctly, for example if the points p 123, p 124, pl34, and p234 are coincident then the satellites SI, S2, S3, S4 are not decoyed and are functioning correctly, the 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 fewer than three are coincident, we can conclude that at least two satellites are being deceived or are not functioning correctly.

[0083] An advantageous method for 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 to be 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 coordinates respectively (XI, Yl, Zl, ....., Xn, Yn, Zn), and the precise time of transmission (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 satellites and 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:

[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+(Y1 -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-xp 1)2+(Y3-yp 1)2+(Z3-zp 1)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 performed:

[0102] a) If, among the m points pl, ..., pm obtained, at least four points are coincident, it can be concluded that the satellites that generated the coincident points are not deceived and are functioning correctly. Step 8 can then be carried out.

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

[0104] - Step 8:

[0105] We can then calculate the position of point P from the coordinates of the undeceived and correctly functioning satellites, in a classical way by solving the system of four unknowns allowing us to obtain the values ​​of the three coordinates of point P and the bias t corresponding to the measurement error of the receiver's reception time.

[0106] A preferred embodiment according to the invention is described below. This description uses [Fig. 1].

[0107] Device comprising

[0108] - a set of n geolocation satellites (with n being at least equal to 4) belonging to one or more geolocation satellite galaxies 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 geolocation satellites regularly transmit several data, the main ones being: the name of the satellite, its position in space (or the means allowing its precise position in space to be calculated), and the precise time of transmission ET,

[0109] - a GNSS antenna designated 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 of calculating its precise position in space), and the exact time of transmission HE of said data received by the ANT antenna,

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

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

[0113] - a means of calculating the approximate distances dl, ..., dn using respectively 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 x 10⁸ meters per second, according to the following formulas:

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

[0115] .......

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

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

[0118] - a calculation method, for each of the m satellite triplets comprising the 3 satellites Sr, Ss, and St, including respectively for each satellite the emission time HEr, HEs, HEt, each satellite having the coordinates respectively Xr, Yr, Zr, Xs, Ys, Zs, and Xt, Yt, Zt, and from the approximate time of signal reception on the antenna HRr, HRs, HRt, (r, s, and t being three different integers between 1 and n), allowing us 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 solving the following system called here the 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 by 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 resulting from the solution of the system of the three preceding equations considering the satellites SI, S2, and S3 and the distances cl,c2, and c3, and for example the point pl24 is the point resulting from the solution of the system of the three preceding 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-coordinate pi points coincident, 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,

[0125] - a means of selecting the decoy and / or non-functioning satellite(s) correctly from the nature of the non-coincident pi points, and the undeceived satellites, and / or functioning correctly from the nature of the coincident pi points,

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

[0127] And following these steps:

[0128] - Step 1: the value of n is initially chosen to be 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 coordinates respectively (XI, Yl, Zl, ....., Xn, Yn, Zn), and the precise time of emission (respectively HE1, ...., HEn), thus that the approximate arrival time of the signals on the antenna (HR1, HRn) emitted by these n satellites,

[0132] - Step 5: We calculate the approximate distances dl, ..., dn existing between the n satellites and 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:

[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+(Y1 -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 performed:

[0146] a) If, among the m points pl, ..., pm obtained, at least four points are coincident, it can be concluded that the satellites that generated the coincident points are not deceived and are functioning correctly. Step 8 can then be carried out.

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

[0148] - Step 8:

[0149] We can then calculate the position of point P from the coordinates of the undeceived and correctly functioning satellites, in a classical way by solving the system of four unknowns allowing us to obtain the values ​​of the three coordinates of point P and the bias t corresponding to the measurement error of the receiver's reception time.

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

[0151] Actual tests have been carried out and have made it possible to verify the relevance and accuracy of the device and the method which is the subject of this patent.

[0152] A person 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 marine vehicles or even on fixed installations.

Claims

[Claim 1] Demands A satellite geolocation method comprising a satellite geolocation device for calculating the position of a point (P) on an aircraft, in real time, with high accuracy, even in the presence of one or more spoofed emissions or emissions 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 geolocation satellite galaxies 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 said geolocation satellites regularly emitting 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 broadcast (ET), - a GNSS antenna designated (ANT) placed at point (P) of the aircraft, - a receiver connected to the antenna (ANT), and capable of receiving data transmitted by geolocation satellites and in particular for each satellite the name of the satellite, its position in space (or the means of calculating its precise position in space), and the exact time of transmission (ET) of said data received by the antenna (ANT), - a means of selecting n satellites denoted (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, respectively denoted (HE1), ..., (HEn), and the coordinates respectively of its position (or the means of calculating the exact position of each satellite) denoted (XI), (Yl), (Zl), ..., (Xn), (Yn), (Zn), - said receiver comprising a means for measuring the approximate time of reception on the antenna (ANT), respectively designated (HR1), ..., (HRn), of the signals sent by each selected satellite (SI), ..., (Sn), - a means of calculating the approximate distances (dl), (dn) using respectively the time difference between the precise time of emission (HE1), ..., (HEn) and the approximate time of reception (HR1), ..., (HRn) and using for the speed (c) of propagation of the electromagnetic background a predetermined value (c) for example 2.99 x 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 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)!), - a calculation method, for each of the m triplets of satellites comprising the 3 satellites (Sr), (Ss), and (St), comprising respectively for each satellite the transmission time (Her), (HEs), (Het), each satellite having 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), allowing the definition of 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 solving 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 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 resulting from the solution of the system of the three preceding equations considering the satellites (SI), (S2), and (S3) and the distances (c1), (c2), and (c3), and for example the point (pl24) is the point resulting from the solution of the system of the three preceding equations considering the satellites (SI), (S2), and (S4) and the distances (cl), (c2), and (c4), - a means of grouping coincident (pi) points and non-coincident (pi) points, by calculating the distances between them two by two points (pi) and determining respectively the distances less than or equal to a predetermined distance (D) and those greater than said distance (D), - a means of selecting the decoy satellite(s) and / or not functioning correctly from the nature of the non-coincident points (pi), and the non-decoy satellite(s), 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 among the non-decoy satellites and using a system of 4 equations with four unknowns which are the three spatial coordinates of the point (P) and the measurement error (or bias) of the time of reception of the signals, and / or by averaging the coordinate values ​​found taking into account several quadruplets of non-decoy satellites. and including 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 with coordinates respectively (XI, Yl, Zl, ....., Xn, Yn, Zn), and the precise time of transmission respectively (HE1, ...., HEn), as well as the approximate time of arrival of the signals on the antenna (HR1, ...., HRn) emitted by 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) to be equal to a value between 2.95x108 meters per second and 3.05x108 meters per second, for example 2.99x108 meters per second, following the following formulas: dl=c*(HRl-HEl) dn=c*(HRn-HEn) - Step 6: By 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 Fl function to obtain the three coordinates (xpl, ypl, zpl, ...., xpm, ypm, zpm) of the m points pl, ..., pm: dp 12=(X 1 -xp 1 )2+(Y 1 -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-1 -xpm)2+( Y m-1 -ypm)2+(Z m-1 -zpm)2 dp32=(Xm-xpm)2+(Ym-ypm)2+(Zm-zpm)2 - Step 7: The following check is performed: a) If, among the m points (pl), ..., (pm) obtained, at least four points are coincident, we can conclude that the satellites that generated the coincident points are not misled and are functioning correctly. We can then perform 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 being deceived and / or are not functioning correctly. It is then necessary to return to step 2. - Step 8: We can then calculate the position of point (P) from the coordinates of the undeceived and correctly functioning satellites, in a classic way by solving the system of four unknowns allowing us to obtain the values ​​of the three coordinates of point (P) and the bias (t) corresponding to the measurement error of the receiver's reception time.