METHOD OF COLLABORATIVE DETERMINATION OF POSITIONING ERRORS OF A SATELLITE-BASED NAVIGATION SYSTEM

• US 20170307761A1
• Filed: 09/02/2015
• Published: 10/26/2017
• Est. Priority Date: 09/05/2014
• Status: Active Grant

• Current Assignee: Centre National D'Etudes Spatiales
• Original Assignee: Centre National D'Etudes Spatiales
• Inventors: SCOT, Gal, LAURICHESSE, Denis
• Granted Patent: US 10,641,902 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 19/07 providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude

Abstract

The positioning signals broadcast by GNSS constellations are affected by significant errors, notably due to the crossing of the ionospheric layer or of the tropospheric layer. Several unwieldy means have been deployed to provide professional users with corrections of said errors. These means, however, all require the knowledge of at least one precise reference point at a given distance. According to the invention, positioning receivers that are not very precise, such as smartphones, present in a geographical zone, of unknown precise position, can contribute to the production of precise atmospheric error corrections if said receivers are sufficiently numerous.

Claims

1. A method of determination by a computer server of errors in calculating a position calculated by user receivers of positioning signals received from at least one constellation of satellites in a determined geographical zone, said method comprising:

determining a list of contributing receivers of positioning signals situated in said geographical zone, a position of said contributing receivers not being known a priori;

extracting, for each of the contributing receivers Ri, code Ci and phase Φ

_i data of at least one channel of the contributing receiver;

calculating an atmospheric error Ii applicable to each contributing receiver Ri on the basis of said code Ci and phase Φ

_i data;

calculating an atmospheric error I(Zj) applicable in the zone Zj, on the basis of the errors Ii applicable to the contributing receivers Ri.

2. The method of claim 1, wherein calculating the atmospheric error Ii consists in calculating only the ionospheric error for all the contributing receivers Ri.

3. The method of claim 1, wherein calculating the atmospheric error Ii consists in calculating at least the tropospheric error for at least one contributing receiver Ri.

4. The method of claim 3, wherein the tropospheric error for the at least one contributor receiver Ri is calculated as the sum of a first delay termed the wet delay and of a second delay termed the hydrostatic delay SHD.

5. The method of claim 1, wherein calculating the atmospheric error I(Zj) receives as input the ionospheric errors of the contributing receivers Ri and a tropospheric error applicable in the geographical zone Zj originating from an external source of provisioning information.

6. The method of claim 1, wherein determining at least one part of the list of contributing receivers Ri situated in said geographical zone uses data of localization of said receivers in relation to at least one base station of a cellular radiocommunications network.

7. The method of claim 1, further comprising classifying pairs of code Ci and phase Φ

_i data of channels of a receiver Ri, said classifying using a weighted combination of criteria comprising criteria representative of one or more of a signal-to-noise ratio of the channel or an elevation of the satellite axis of the channel.

8. The method of claim 1, wherein calculating an atmospheric error Ii applicable to the receiver Ri comprises subtracting said code Ci and phase Φ

_i data.

9. The method of claim 8, wherein an integer ambiguity of the phase Φ

_i is neglected.

10. The method of claim 1, further comprising calculating a quality index IQ(Ii) of the atmospheric error Ii applicable to the receivers Ri.

11. The method of claim 10, wherein the quality index IQ(Ii) is calculated by a weighted combination of criteria comprising criteria representative of one or more of a signal-to-noise ratio of a channel of the receiver Ri, an elevation of a satellite axis acquired by the receiver Ri, a number of satellite axes acquired.

12. The method of claim 10, wherein the quality index IQ(Ii) further depends on parameters characterizing one or more of a hardware or a software configuration of the receiver Ri.

13. The method of claim 10, wherein the errors Ii of the receivers Ri whose quality index IQ(Ii) is less than a threshold value Thresh1 have a zero weighting in calculating an atmospheric error I(Zj) applicable in the zone Zj.

14. The method of claim 10, wherein the atmospheric error I(Zj) applicable in the zone Zj is a linear combination of the errors Ii weighted by the quality indices IQ(Ii).

15. The method of claim 10, further comprising filtering values I(Zj) by a model of atmospheric errors.

16. The method of claim 1, further comprising determining a confidence indicator of the atmospheric error I(Zj).

17. The method of claim 13, wherein the confidence indicator of the ionospheric error I(Zj) is dependent on a number Nj of contributing receivers Ri whose quality index IQ(Ii) is greater than Thresh1.

18. The method of claim 1, wherein the atmospheric error I(Zj) is replaced, when its confidence indicator is less than a predetermined threshold value Thresh2, by a value I(Z) calculated by one or more of a spatial or a temporal interpolation within a set of values of atmospheric errors calculated for neighbouring geographical zones or periods.

19. The method of claim 1, further comprising making values of atmospheric errors I(Zj) available to the user receivers.

20. The method of claim 19, further comprising acquiring by the user receivers of a position determined by a server.

21. The method of claim 19, further comprising calculating a position corrected by fusion of the PVT data of the user receiver and of the values of atmospheric errors I(Zj).

28. A method of correcting a position calculation performed by a user receiver of positioning signals received from at least one constellation of satellites in a determined geographical zone, said method comprising:

acquiring from a server according to claim 25 an atmospheric error I(Z) calculated by a procedure of fusion according to claim 1 by said server of atmospheric errors determined from a plurality of contributing receivers situated in the geographical zone, a position of said contributing receivers not being known a priori;

fusing the atmospheric error acquired with the PVT point calculated by the user receiver.

22. A collaborative system for aiding the positioning of user receivers of positioning signals received from at least one constellation of satellites in at least one geographical zone, said system comprising a plurality of hardware and computer code elements configured to:

determine a list of contributing receivers of positioning signals situated in said geographical zone, a position of said contributing receivers not being known a priori;

extract, for each of the contributing receivers Ri, code Ci and phase Φ

_i data of at least one channel of the receiver;

calculate an atmospheric error Ii applicable to the contributor receivers Ri from said code Ci and phase Φ

_i data;

calculate an atmospheric error I(Zj) applicable in the zone Zj, from the errors Ii of the contributor receivers Ri;

make available to the user receivers at least one result of the calculation of atmospheric error in said at least one geographical zone.

23. The system of claim 22, wherein a processor of at least one contributing receiver Ri is configured to perform the calculation of atmospheric error Ii applicable in the zone to said contributing receiver Ri from said code Ci and phase Φ

_i data, the result of said calculation being transmitted to a server through a communication link.

24. The system of claim 22, wherein code Ci and phase Φ

_i data of at least one channel of at least one contributing receiver Ri are transmitted to a server through a communication link, a processor of said server being configured to perform the calculation of atmospheric error Ii applicable in the zone to said contributor receiver Ri from said code Ci and phase Φ

_i data.

25. A server of positioning data, said server comprising:

circuit logic configured to determine a list of contributing receivers situated in a geographical zone;

processing logic configure to acquire with a determined frequency temporal sequences of data transmitted by the contributing receivers Ri of said list, said temporal sequences comprising one or more of;

code and phase of at least one channel of each of the contributing receivers Ri, or

a datum calculated from said code and said phase

data logic configured to calculate a temporal sequence of atmospheric errors applicable in said geographical zone;

a link to make available to user receivers said temporal sequence of atmospheric errors.

26. A contributing receiver of positioning signals, comprising:

a memory for storing temporal sequences of data comprising;

one or more of code and phase of at least one channel of the receiver, or a datum calculated from the code and of the phase,

and at least one quality index of said data, said index being chosen from a group comprising a signal-to-noise ratio of the channel, an elevation of a satellite axis corresponding to said channel, and a number of satellite axes acquired;

a communication link configured to teletransmit said temporal sequences stored in a memory of the receiver to a preidentified remote server with a predetermined frequency.

27. A user receiver of positioning signals, comprising:

a communication link configured to tele-receive with a predetermined frequency temporal sequences of data of the server of positioning data of claim 26;

circuit logic configured to calculate a corrected position from a PVT point calculated by the receiver and said temporal sequences of data.