AUTONOMOUS VEHICLE POSITIONING DEVICE AND METHOD

Abstract

The present invention relates to a positioning device (110) configured to determine the location of a vehicle from positioning signals broadcast by at least one constellation (200) of satellites, the vehicle being stationary or moving on the tracks of a given network (300), the positioning device (110) comprising: a first unit configured to, at a given measurement time, determine a plurality of possible current positions of the vehicle and determine a plurality of timestamp values, the plurality of timestamp values ​​being determined in a given time interval, the first unit being further configured to: generate, for each possible current position of the vehicle, local replicas of positioning signals, each of the local replicas being associated with a timestamp value from among the plurality of timestamp values ​​and with a satellite for the purpose of at least one constellation (200) of satellites;receive, at each timestamp value among the plurality of timestamp values, positioning signals broadcast by one or more satellites (201) for the purpose of at least one constellation (200) of satellites; calculate, for each possible current position of the vehicle, elementary likelihoods, each of the elementary likelihoods being calculated by executing a correlation function between a received positioning signal and the corresponding generated local replica; determine, for each possible current position of the vehicle, multi-satellite likelihoods, each of the multi-satellite likelihoods being determined for a given timestamp value from the corresponding elementary likelihoods;a second unit configured to determine a most likely position and a most likely timestamp value, respectively among the plurality of possible current positions and among the plurality of timestamp values, by comparing multi-satellite likelihoods. (Figure 1);

Description

Title of the invention: AUTONOMOUS VEHICLE POSITIONING DEVICE AND METHOD technical field

[0001] The invention relates, generally, to positioning systems and, in particular, to a device and method for autonomous vehicle positioning using positioning signals provided by at least one satellite constellation and not requiring a previous position or train movement. BACKGROUND

[0002] Rail transport has become an efficient solution for transporting both people and goods. Compared to road transport, for example, rail transport has the advantage of being economical, more environmentally friendly, capable of carrying heavy loads, and more reliable since trains do not have to share tracks with the public like trucks on the road. These advantages have directly resulted in the rapid growth of rail network development over the last two decades, particularly in countries experiencing significant social and / or economic progress. In order to meet the ever-increasing demand for more efficient, faster, and cleaner rail transport, the number of trains sharing the same rail network, as well as their speed, is constantly increasing.Thus, managing a railway network has become a task of paramount importance in order to guarantee a certain level of safety, particularly in the case of passenger transport. For the effective management of a railway network, it is imperative to be able to precisely locate, in real time, each train in operation or stopped on the tracks.

[0003] A known solution for determining the location of a train traveling on the tracks of a railway network consists of installing electronic beacons along the tracks, the electronic beacons being connected wirelessly or via a wired connection to a central control unit. The operating principle of an electronic beacon is to detect, by means of a mechanical or electronic mechanism, any train passing over it. When a train is detected, the electronic beacon immediately emits a detection signal that contains an identifier for the electronic beacon and may include information concerning the train passing over the beacon. In some cases, the electronic beacons can be configured to interact, i.e., exchange signals, with the train passing over the beacon. In such cases, the train passing over the beacon may transmitting detection signals to the central control unit is a complex process. Implementing and maintaining such a solution quickly becomes expensive, given the large number of electronic beacons required in both high-speed rail networks, where the distance between adjacent stations is usually more than a few kilometers, and metro networks, where high accuracy is essential despite the short distance between stations. This solution also has the drawback of being compatible only with moving trains, whereas it is also necessary to locate stationary trains. Furthermore, with this system, it is impossible to locate a moving or stationary train between two adjacent electronic beacons.

[0004] Another known solution for determining the location of a train in motion or stopped on the tracks of a railway network is to use Global Navigation Satellite Systems (GNSS) by equipping each train with a GNSS receiver. This solution eliminates the need to install beacons along the tracks. Generally, a GNSS receiver operates independently of the railway network by calculating a three-dimensional (3D) position (latitude, longitude, and altitude) of the corresponding train relative to a terrestrial reference system. In order to calculate an exact 3D position of a corresponding train, a GNSS receiver must be located within a clear line of sight of at least three GNSS satellites.Such a requirement is, however, difficult to meet consistently over time in the context of rail transport, where trains travel between mountains and buildings, and pass through bridges and tunnels. The presence of such obstacles prevents GNSS signals from reaching the GNSS receiver, resulting in inaccurate train positioning. Furthermore, even in the absence of obstacles between the GNSS satellites and the GNSS receiver, accurate train positioning requires precise synchronization between the clocks on board the GNSS satellites, which govern the generation of GNSS signals, and the clock in the GNSS receiver, which is necessary for the correct decoding of the received GNSS signals. Generally, GNSS satellites are equipped with very stable atomic clocks, while GNSS receivers use less stable and less precise clocks that can be subject to time drift.For example, a time drift of 1 pm in the GNSS receiver's clock can result in tens of meters of inaccuracy in the positioning of the corresponding train. Such a level of inaccuracy makes the use of a simple GNSS receiver incompatible with rail transport where high precision is required, for example, to determine which track in a station a train is stopped on.

[0005] An improved positioning device, which does not have the disadvantages of the current state of the art, is therefore necessary. SUMMARY

[0006] To solve these and other problems, a positioning device is proposed that is configured to determine the location of a vehicle from positioning signals broadcast by at least one satellite constellation, whether the vehicle is stationary or moving on the tracks of a given network. The positioning device comprises: - a first unit configured to, at a given measurement time, determine a plurality of possible current vehicle positions and determine a plurality of timestamp values, the plurality of timestamp values ​​being determined within a given time interval, the first unit being further configured to: • generate, for each possible current position of the vehicle, local replicas of positioning signals, each of the local replicas being associated with a timestamp value from among the plurality of timestamp values ​​and with a satellite for the purpose of at least one satellite constellation; • receive, at each timestamp value among the plurality of timestamp values, positioning signals broadcast by one or more satellites for the purpose of at least one satellite constellation; • calculate, for each possible current position of the vehicle, elementary likelihoods, each of the elementary likelihoods being calculated by executing a correlation function between a received positioning signal and the corresponding generated local replica; • determine, for each possible current position of the vehicle, multi-satellite likelihoods, each of the multi-satellite likelihoods being determined for a given timestamp value from the corresponding elementary likelihoods; - a second unit configured to determine a most likely position and a most likely timestamp value, respectively among the plurality of possible current positions and among the plurality of timestamp values, by comparing multi-satellite likelihoods.

[0007] According to certain embodiments, the positioning device may further comprise a cartographic database including position information of the given network's tracks, the second unit being configured, in addition, to determine the track section on which the vehicle is located by accessing the map database and using the most likely position determined.

[0008] According to certain embodiments, the cartographic database may also include a representation of the environment around the roads of the given network.

[0009] According to some embodiments, the first unit can be further configured to access the map database in order to determine one or more propagation characteristics of each of the received positioning signals, the first unit being further configured to exclude one or more positioning signals from the calculation of elementary likelihoods according to their propagation characteristics.

[0010] According to some embodiments, the first unit can be configured to, when the vehicle is in motion, determine the plurality of possible current positions using a PVT technique in conjunction with a plurality of positioning signals.

[0011] According to some embodiments, the first unit can be configured to, when the vehicle is stopped in a parking lane among a plurality of adjacent parking lanes, determine the plurality of possible current positions by assigning a possible current position to each of the adjacent parking lanes.

[0012] According to some embodiments, the first unit can be configured, furthermore, to determine the given time interval as a function of a temporal integrity protection radius associated with at least one satellite constellation.

[0013] According to some embodiments, the first unit can be configured, furthermore, to determine the plurality of timestamp values ​​by performing regular sampling over the given time interval.

[0014] According to some embodiments, the first unit can be configured to receive positioning signals from at least two satellite constellations, the first unit being further configured to separately process the positioning signals broadcast by each of the satellite constellations, the second unit being configured to determine a most likely position and a most likely timestamp value for each of the satellite constellations, the second unit being further configured to determine a final most likely position among the most likely positions determined.

[0015] According to some embodiments, the second unit can be configured to use a selection criterion to determine the most likely final position, the selection criterion being chosen from a plurality of selection criteria which includes: - the number of satellites per constellation contributing to the determination of each most likely position, the final most likely position being determined using a maximum number of satellites in view; and - the duration of the given time interval, the most likely final position being determined using the satellite constellation associated with the shortest given time interval.

[0016] According to some embodiments, the second unit can be further configured to generate an alert notification if it is unable to determine the most likely position of the vehicle within a predefined time interval.

[0017] The invention also relates to a method for determining the location of a vehicle using positioning signals broadcast by at least one satellite constellation. The method includes the following steps: - determine a plurality of possible current positions of the vehicle and determine a plurality of timestamp values ​​within a given time interval; - generate, for each possible current position of the vehicle, local replicas of positioning signals, each of the local replicas being associated with a timestamp value from among the plurality of timestamp values ​​and with a satellite for the purpose of at least one satellite constellation; - receive, at each timestamp value among the plurality of timestamp values, positioning signals broadcast by one or more satellites for the purpose of at least one satellite constellation; - calculate, for each possible current position of the vehicle, elementary likelihoods, each of the elementary likelihoods being calculated by executing a correlation function between a received positioning signal and the corresponding generated local replica; - determine, for each possible current position of the vehicle, multi-satellite likelihoods, each of the multi-satellite likelihoods being determined for a given timestamp value from the corresponding elementary likelihoods; - determine the most likely position and the most likely timestamp value, respectively from the plurality of possible current positions and from the plurality of timestamp values, by comparing multi-satellite likelihoods. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated into this memorandum and form part thereof, illustrate various embodiments of the invention and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the embodiments of the invention.

[0019] Fig. 1 represents a vehicle positioning system according to certain embodiments of the invention;

[0020] [Fig.2] schematically illustrates the structure of a positioning device according to certain embodiments of the invention;

[0021] [Fig.3] illustrates the acquisition of positioning signals according to one embodiment of the invention;

[0022] [Fig.4] is a flowchart illustrating a positioning method according to an embodiment of the invention. DETAILED DESCRIPTION

[0023] Figure 1 illustrates a vehicle localization system 10 in which a positioning device 110 can be used, according to certain embodiments of the invention. The vehicle localization system 10 comprises several tracks belonging to a given network 300, the tracks being arranged according to a given architecture. The vehicle localization system 10 further comprises one or more vehicles 100, each of the vehicles 100 being restricted to operating exclusively on the tracks of the given network 300. For example, the tracks of the given network 300 may correspond to the tracks of a rail transport system. In such an example, the vehicles 100 are rail vehicles 100 which may be, without limitation, trains or subway trains.Each of the 100 vehicles includes a positioning device 110 which can be configured to determine the instantaneous position of the corresponding vehicle using positioning signals from an external source.

[0024] The vehicle positioning system 10 further comprises a constellation 200 of satellites including several satellites 201. The number of satellites 201 forming the constellation, as well as their orbital characteristics, can be predetermined so as to ensure that each positioning device 110 is constantly covered by at least one satellite of the constellation. This enables the positioning device 110 to continuously receive positioning signals from at least one satellite of the constellation 200. It should be noted that a positioning signal emitted by a satellite of the constellation 200 may be subject, before reaching the positioning device 110, to various distortions such as multipath propagation interference. These distortions can be caused by several phenomena, including diffraction by natural obstacles or buildings. Some of these distortions may be deterministic, in which case they can simply be compensated for by the positioning device 110. Other distortions, however, are probabilistic and require highly complex processing for the correct decoding of the positioning signals. Furthermore, each of the 201 satellites in the constellation 200 includes an onboard clock configured to govern the generation of positioning signals. The onboard clock of each satellite in the constellation 200 can advantageously be an atomic clock, which offers greater stability and accuracy compared to other types of clocks.

[0025] The given network 300 includes several switches 304 inserted between the tracks and configured to guide vehicles 100 from one track to another. The use of switches 304 allows the vehicles 100 to share common tracks 302. In the example of a railway network 300, a switch is a mechanical installation enabling railway vehicles 100 to be guided from one track to another.

[0026] The given network 300 further comprises several parking lanes 301 used to park vehicles 100 when they are not in use and / or when they are out of service, for example. In addition, some of the parking lanes 301 may be placed parallel to a common track 302 and connected to it by means of a switch. Generally, a parking lane can be considered as a starting or ending point for one or more corresponding vehicles 100. A unique identifier may be assigned to each of the parking lanes 301. In some embodiments, the positioning device 110 may be configured to determine, when the corresponding vehicle is stopped on a parking lane, the parking lane on which the corresponding vehicle is stopped by returning its unique identifier, for example.

[0027] The given network 300 further comprises several common tracks 302 on which multiple vehicles 100 can travel successively. In the example of a railway network 300, several railway vehicles 100 can travel on the same track in a common direction of travel. Moreover, each of the common tracks 302 can be considered as an association of a plurality of sections, each section being assigned a unique identifier. In certain embodiments, the positioning device 110 can be configured so that, when the corresponding vehicle is moving on a common track 302, it determines the section of the common track 302 on which the corresponding vehicle is located by returning its unique identifier, for example.

[0028] The given network 300 may further include one or more stations where a vehicle may temporarily remain to pick up passengers, for example. Moreover, each of the stations may include several station tracks 303 parallel; each of the station tracks 303 can, for example, be associated with a platform. A unique identifier can advantageously be assigned to each of the station tracks 303. In certain embodiments, the positioning device 110 can be configured to, when the corresponding vehicle enters a station, determine the station track on which the corresponding vehicle is moving by returning its unique identifier, for example.

[0029] In certain embodiments of the invention, the positioning device 110 can be configured to determine a parking lane, a section of a common lane 302 or a station lane of the corresponding vehicle using one or more positioning signals provided by the constellation 200 of satellites and using the given network architecture 300.

[0030] Figure 2 illustrates the structure of a positioning device 110 according to certain embodiments of the invention. The following description of the positioning device 110 relates to a railway network 300. Those skilled in the art will readily understand that the positioning device 110, according to the various embodiments of the invention, can easily be applied to other types of transport networks where the vehicles 100 are restricted to operating exclusively on the tracks of the given network 300. The positioning device 110 advantageously comprises a first unit 111, the first unit 111 being configured to determine, at a given measurement time, several possible current positions of the railway vehicle. The possible current positions of the railway vehicle can be determined on the basis of one or more parameters such as the state of the railway vehicle, e.g., whether stopped or moving, the last known position of the railway vehicle, the speed of the railway vehicle, etc.For example, when the rail vehicle is parked on one of a plurality of adjacent parking tracks 301, the first unit 111 can be configured to determine the possible current positions of the rail vehicle by assigning a possible current position to each of the adjacent parking tracks 301. In another example, where the rail vehicle is traveling on a common track 302 of the rail network 300, the first unit 111 can be configured to determine the possible current positions of the rail vehicle by assigning a possible current position to each of the sections of the common track 302. Given the length of a rail vehicle, a possible current position of a rail vehicle may correspond precisely to the possible current position of its locomotive.

[0031] The positioning device 110 further comprises a clock that governs the decoding of the positioning signals provided by the constellation of 200 satellites. In one embodiment of the invention, the clock with which the positioning device 110 is equipped is synchronized with the clocks on board the satellites of the constellation of 201 satellites. constellation 200 which govern the generation of positioning signals. In such an embodiment, the first unit 111 is further configured to determine a timestamp value which can correspond to the given measurement time.

[0032] In another embodiment of the invention, the clock with which the positioning device 110 is equipped is not synchronized with one or more clocks on board the satellites 201 of the constellation. In such an embodiment, the first unit 111 can be configured to determine a given time interval based on the time difference between the two clocks. The first unit 111 can also be configured to determine a plurality of timestamp values ​​within the given time interval. For example, the timestamp values ​​can be obtained by linear sampling of the given time interval. The given time interval can also be determined based on the speed of the rail vehicle. For example, the higher the speed of the rail vehicle, the shorter the given time interval.A special case arises when the rail vehicle is stopped; the given time interval can be as long as possible according to predefined positioning time criteria.

[0033] The first unit 111 can be further configured to generate, for each possible current position of the rail vehicle, one or more local replicas of positioning signals, each local replica of positioning signals being associated with a timestamp value and a satellite in view of the constellation of 200 satellites. Thus, the number of local replicas of positioning signals generated by the first unit 111 for a given possible current position and a given timestamp value corresponds to the number of satellites 201 in view. Each of the local replicas of positioning signals is generated by the first unit 111 based on the position of the corresponding satellite in view, which is assumed to be precisely known to the first unit 111 of the positioning device 110.In general, received navigation messages include an ephemeris field containing information about the position of the satellite emitting the positioning signal, and may also include an almanac field containing information about the orbit of each satellite in the constellation.

[0034] The first unit 111 can be further configured to receive, at each timestamp value of the plurality of timestamp values, positioning signals broadcast by one or more satellites 201 of the constellation, the satellite(s) 201 of the constellation 200 being visible to the positioning device 110. Each of the positioning signals can consist of a navigation message modulated by a spreading sequence, generally pseudo-random noise (PN). A positioning signal can undergo various distortions before reaching the positioning device 110. The first unit 111 can advantageously be configured, in addition, to compensate for such distortions before using the positioning signals to determine the location of the corresponding railway vehicle.

[0035] The first unit 111 can be configured, furthermore, to calculate, for each possible current position of the railway vehicle, elementary likelihoods, each of the elementary likelihoods being calculated by performing a correlation function between a positioning signal and its local replica for a given timestamp value of the plurality of timestamp values ​​and a given satellite in view of the constellation of 200 satellites.

[0036] The first unit 111 can, moreover, be configured to determine, for each possible current position of the rail vehicle, one or more multisatellite likelihoods, each of the multisatellite likelihoods being determined for a given timestamp value using the corresponding elementary likelihoods, i.e., the elementary likelihood calculated for the given timestamp value. For example, a multisatellite likelihood can be determined as a quadratic sum of all the corresponding elementary likelihoods.

[0037] The positioning device 110 further comprises a second unit 112, the second unit 112 being configured to receive the multisatellite likelihoods already determined. Furthermore, the second unit 112 can be configured to determine a most likely possible current position and a most likely timestamp value, respectively, from among the possible current positions and from among the plurality of timestamp values, by comparing the multisatellite likelihoods already determined. For example, the most likely position and the most likely timestamp value may correspond to a maximum multisatellite likelihood.

[0038] The positioning device 110 may further include a map database 113 comprising a representation of the railway network 300. For example, the map database 113 may include the 3D coordinates of the centerline of each of the tracks of the railway network 300. Advantageously, the map database 113 may contain only samples of the track centerlines. This considerably reduces the amount of data contained in the database. Furthermore, the minimum distance between two adjacent samples of the centerline may vary depending on whether or not there is a track ambiguity problem to be resolved. The track ambiguity problem arises, for example, when the rail vehicle is on one of several adjacent parking tracks 301. In this example, the distance The minimum distance can be chosen to be less than the minimum distance separating two adjacent tracks, for example, less than four meters. In a scenario where there is no track ambiguity problem, such as when the rail vehicle is traveling on a common track 302, the minimum distance between two adjacent centerline samples can be determined based on a predefined accuracy threshold.

[0039] In one embodiment of the invention, the mapping database 113 may further comprise a representation of the environment 400 surrounding the tracks of the railway network 300. Such a representation may include elements of the surrounding environment 400 that could have an impact, i.e., cause distortion, on the positioning signals before they reach the positioning device 110. For example, only those elements of the surrounding environment 400 located within a predefined interval centered on the track may be considered. More specifically, the mapping database 113 may contain, for each of the elements considered, several characteristics that may include geometric characteristics (length, height, width, distance from the track centerline, etc.).

[0040] In another embodiment of the invention, the second unit 112 can be further configured to determine the track on which the rail vehicle is located by accessing the mapping database 113 and entering the most likely position already determined. For example, in a scenario where the rail vehicle is parked on one of several parking tracks 301, the second unit 112 can be configured to determine the unique identifier of the parking track on which the rail vehicle is parked. In another scenario, where the rail vehicle is traveling on a common track 302, the second unit 112 can be configured to determine the section of the common track 302 on which the rail vehicle is located.

[0041] In one embodiment of the invention, the first unit 111 of the positioning device 110 can be configured to determine the plurality of possible current positions using a PVT (Position-Velocity-Time) technique consisting of determining distances between the positioning device 110 and each of the satellites 201 in view, such distances being known as "pseudodistances". When three pseudodistances are calculated, the first unit 111 can be configured to determine the 3D coordinates, this representing a possible current position of the rail vehicle, knowing the positions of the satellites 201. When at least four pseudodistances are calculated, the first unit 111 can be configured to determine, from each combination of three pseudodistances, a corresponding possible current position of the vehicle railway. In addition, the first unit 111 of the positioning device 110 can be configured, furthermore, to access the map database 113 in order to reduce the number of possible current positions of the railway vehicle, given that the railway vehicle is restricted to operating only on the tracks of the railway network 300.

[0042] In another embodiment of the invention, the first unit 111 of the positioning device 110 can be configured to determine the plurality of possible current positions using models and / or assumptions that govern the movement of the rail vehicle on the tracks of the railway network 300. The determination of the plurality of possible current positions can also advantageously take into account information from external sources that can be provided by other devices with which the rail vehicle is equipped. Such information from external sources can include the instantaneous speed of the train, an approximate location of the rail vehicle as determined by an inertial measurement unit (IMU), and / or a previously determined location of the rail vehicle.In addition, the first unit 111 of the positioning device 110 can be configured, furthermore, to access the mapping database 113 in order to reduce the number of possible current positions of the railway vehicle, given that the railway vehicle is restricted to operating only on the tracks of the railway network 300.

[0043] The first unit 111 of the positioning device 110 can be configured to determine the given time interval for a given constellation 200 of satellites based on a temporal integrity protection radius, which can be calculated from the time data of a RAIM (Receiver Autonomous Integrity Monitoring) function integrated or external to the positioning device 110.

[0044] In one embodiment of the invention, the positioning device 110 can be configured to receive, at a given measurement time, positioning signals provided by satellites 201 belonging to at least two constellations 200 of satellites 201. In such an embodiment, the positioning device 110 can be configured to independently process the positioning signals provided by each constellation 200 of satellites as described above with respect to a single constellation 200 of satellites, thereby determining a most probable current position for each constellation 200 of satellites. Furthermore, the positioning device 110 can be configured to select a final most probable current position from among the plurality of most probable current positions determined.Such a selection operation can, for example, be carried out on the basis of a criterion of . Selection. The selection criterion could, for example, be the number of 201 satellites in sight contributing to the determination of a corresponding most likely position. In this case, the most likely position determined using the maximum number of 201 satellites can be taken as the final most likely position.

[0045] In another embodiment of the invention, the selection criterion used by the positioning device 110 to determine a most likely final position from among a plurality of most likely positions may be the duration of the given time interval. In this case, the most likely possible current position associated with the shortest given time interval may be taken as the most likely final position.

[0046] In one embodiment of the invention, the positioning device 110 can be configured to generate an alert notification when it is unable to locate the corresponding rail vehicle within a predefined measurement time interval, the predefined measurement time interval being measured from the given measurement time. This can occur, for example, when the rail vehicle enters areas of reduced coverage and / or adverse weather conditions. The duration of the predefined measurement time interval can depend on whether the rail vehicle is stationary or moving. The generated alert notification can, for example, be transmitted to the driver of the rail vehicle.

[0047] Figure 3 illustrates the acquisition of positioning signals according to one embodiment of the invention. The positioning device 110 receives positioning signals from two satellites 201 within line of sight belonging to a common constellation 200 of satellites. The positioning signals broadcast by one of the two satellites 201 reach the positioning device 110 by line-of-sight propagation, that is, the positioning signals propagate along a direct path from the satellite to the positioning device 110. The positioning signals broadcast by the other satellite undergo multipath propagation before reaching the positioning device 110.The first unit 111 of the positioning device 110 can be configured to access the mapping database 113 and determine the propagation characteristics of each of the received positioning signals, knowing, for example and without limitation, the position of the corresponding satellite, the current possible position of the rail vehicle, and the environmental characteristics 400 of the surrounding area provided by the mapping database 113. The first unit 111 can also be configured to exclude one or more positioning signals from the calculation of elementary likelihoods based on their propagation characteristics. For example, the first unit 111 can include in the calculation of elementary likelihoods only those positioning signals reaching the device. Positioning of 110 according to line-of-sight propagation. This increases the accuracy of the railway vehicle's positioning.

[0048] Figure 4 is a flowchart illustrating a method for positioning a railway vehicle, which can be implemented at the level of the positioning device 110 according to one embodiment of the invention. In step 401, a plurality of possible current positions of a railway vehicle moving on the tracks of a railway network 300 are determined at a given measurement time. Neither a previous position nor a movement of the train is required. The plurality of possible current positions can be determined using a PVT technique in conjunction with a plurality of positioning signals broadcast by satellites 201 from at least one constellation 200 of satellites. Step 401 further consists of determining a plurality of timestamp values, the timestamp values ​​being determined within a given time interval.For example, the plurality of timestamp values ​​can be determined by regular or irregular sampling of the given time interval. Furthermore, the given time interval can be determined in advance based on a temporal integrity protection radius associated with at least one constellation of 200 satellites.

[0049] In step 402, local replicas of positioning signals are generated for each possible current position of the rail vehicle, each of the local replicas being associated with a timestamp value from the plurality of timestamp values ​​and with a satellite for the purpose of at least a constellation of 200 satellites.

[0050] At step 403, positioning signals broadcast by the 201 satellites for the purpose of at least one 200 satellite constellation are received at each timestamp value of the plurality of timestamp values.

[0051] In step 404, elementary likelihoods are calculated for each possible current position of the railway vehicle. Each elementary likelihood is calculated by performing a correlation function between a received positioning signal and the corresponding generated local replica.

[0052] In step 405, multisatellite likelihoods are determined for each possible current position of the rail vehicle. Each multisatellite likelihood is determined for a given timestamp value from the corresponding elementary likelihoods. Furthermore, a multisatellite likelihood can be determined as a quadratic sum of all the corresponding elementary likelihoods.

[0053] In step 406, a most likely position and a most likely timestamp value, respectively from among the plurality of possible current positions and from among the plurality of timestamp values, are determined by comparing the multisatellite likelihoods. For example, the most likely position and the The most likely timestamp value may correspond to a multi-satellite maximum likelihood. The most likely position is the final most likely position if the positioning signals are broadcast from 201 satellites belonging to a common constellation of 200 satellites.

[0054] In one embodiment of the invention, the positioning method may further include a step of determining, if the railway vehicle is stopped, the parking track on which the railway vehicle is parked by accessing a map database 113.

[0055] In another embodiment of the invention, the positioning method may further include a step of determining, if the railway vehicle is in motion, the section of the track on which the railway vehicle is located by accessing a cartographic database 113.

[0056] It should be noted that the functions, actions, and / or operations specified in the flowcharts, sequence diagrams, and / or functional diagrams may be performed in a different order, executed successively, and / or executed simultaneously according to the embodiments of the invention. Furthermore, the flowcharts, sequence diagrams, and / or functional diagrams may comprise more or fewer blocks than illustrated according to the embodiments of the invention.

[0057] Although embodiments of the invention have been illustrated through the description of various examples, and although these embodiments have been described in ample detail, the applicant does not intend to restrict or limit in any way the scope of the claims attached to such details. Additional advantages and modifications will be immediately apparent to a person skilled in the art. The invention in its more general aspects is, therefore, not limited to the specific details, representative methods, and illustrative examples presented and described.

Claims

1. Demands Positioning device (110) configured to determine the location of a vehicle from positioning signals broadcast by at least two constellations (200) of satellites, the vehicle being stationary or moving on the tracks of a given network (300), the positioning device (110) comprising: a first unit (111) configured to, at a given measurement time, determine a plurality of possible current positions of the vehicle and determine a plurality of timestamp values, the plurality of timestamp values ​​being determined within a given time interval, the first unit (111) being further configured to process separately the positioning signals broadcast by each of the constellations (200) of satellites (201), and for each constellation of satellites: • generate, for each possible current position of the vehicle, local replicas of positioning signals, each of the local replicas being associated with a timestamp value from among the plurality of timestamp values ​​and with a satellite for the constellation (200) of satellites; • receive, at each timestamp value among the plurality of timestamp values, positioning signals broadcast by one or more satellites (201) for the constellation (200) of satellites; • calculate, for each possible current position of the vehicle, elementary likelihoods, each of the elementary likelihoods being calculated by executing a correlation function between a received positioning signal and the corresponding generated local replica; • determine, for each possible current position of the vehicle, multisatellite likelihoods, each of the multisatellite likelihoods being determined for a given timestamp value at starting from the quadratic sum of the corresponding elementary likelihoods; - a second unit (112) configured to, for each of the constellations (200) of satellites (201), determine a most likely position and a most likely timestamp value, respectively among the plurality of possible current positions and among the plurality of timestamp values, by comparing the multi-satellite likelihoods, then to determine a final most likely position among the most likely positions determined for the different constellations (200) of satellites (201).

2. Positioning device (110) according to claim 1, further comprising a map database (113) including position information for the lanes of the given network (300), the second unit (112) being further configured to determine the lane section on which the vehicle is located by accessing the map database (113) and using the most likely position determined.

3. Positioning device (110) according to claim 2, wherein the mapping database (113) further comprises a representation of the environment (400) around the roads of the given network (300).

4. Positioning device (110) according to claim 3, wherein the first unit (111) is further configured to access the mapping database (113) in order to determine one or more propagation characteristics of each of the received positioning signals, the first unit (111) being further configured to exclude one or more positioning signals from the calculation of elementary likelihoods based on their propagation characteristics.

5. Positioning device (110) according to any one of the preceding claims, wherein the first unit (111) is configured to, when the vehicle is in motion, determine the plurality of possible current positions using a PVT technique in conjunction with a plurality of positioning signals.

6. Positioning device (110) according to any one of the preceding claims, wherein the first unit (111) is configured to, when the vehicle is stopped in a parking lane among a plurality of adjacent parking lanes (301), determine the plurality of possible current positions by assigning a possible current position to each of the adjacent parking lanes (301).

7. Positioning device (110) according to any one of the preceding claims, wherein the first unit (111) is further configured to determine the given time interval as a function of a temporal integrity protection radius associated with at least one constellation (200) of satellites.

8. Positioning device (110) according to any one of the preceding claims, wherein the first unit (111) is further configured to determine the plurality of timestamp values ​​by performing regular sampling over the given time interval.

9. Positioning device (110) according to claim 8, wherein the second unit (112) is configured to use a selection criterion to determine the final most likely position, the selection criterion being chosen from among the following criteria: - the number of satellites (201) per constellation (200) contributing to the determination of each most likely position, the final most likely position being determined using a maximum number of satellites (201) in view; and - the duration of the given time interval, the final most likely position being determined using the constellation (200) of satellites associated with the shortest given time interval.

10. Positioning device (110) according to any one of the preceding claims, wherein the second unit (112) is further configured to generate an alert notification if it is unable to determine a most likely position of the vehicle within a predefined time interval.

11. A method for determining the location of a vehicle using positioning signals broadcast by at least two constellations (200) of satellites, the process comprising the following steps: - determine (401) a plurality of possible current vehicle positions and determine a plurality of timestamp values ​​within a given time interval; - to process separately the positioning signals broadcast by each of the satellite constellations, and for each satellite constellation: • generate (402), for each possible current position of the vehicle, local replicas of positioning signals, each of the local replicas being associated with a timestamp value from among the plurality of timestamp values ​​and with a satellite for the constellation (200) of satellites; • receive (403), at each timestamp value among the plurality of timestamp values, positioning signals broadcast by one or more satellites (201) for the constellation (200) of satellites; • calculate (404), for each possible current position of the vehicle, elementary likelihoods, each of the elementary likelihoods being calculated by executing a correlation function between a received positioning signal and the corresponding generated local replica; • determine (405), for each possible current position of the vehicle, multi-satellite likelihoods, each of the multi-satellite likelihoods being determined for a given timestamp value from the quadratic sum of the corresponding elementary likelihoods; - for each of the satellite constellations, determine (406) a most likely position and a most likely timestamp value, respectively among the plurality of possible current positions and among the plurality of timestamp values, by comparing the multi-satellite probabilities, then determine a final most likely position among the most likely positions determined for the different satellite constellations.

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