GEOPOSITIONING METHOD USING ASSISTANCE DATA

• US 20120001799A1
• Filed: 03/11/2010
• Published: 01/05/2012
• Est. Priority Date: 03/13/2009
• Status: Active Grant

• Current Assignee: Centre National D'Etudes Spatiales
• Original Assignee: Centre National D'Etudes Spatiales
• Inventors: Laurichesse, Denis, Mercier, Flavien
• Granted Patent: US 9,519,064 B2
• Time in Patent Office: Days
• US Class Current: 342/357.64
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

In order to enable a geopositioning receiver of a user to resolve phase ambiguities without necessarily using multi-frequency observations, assistance data is developed thanks to measurements made at a reference network (10, 12, 14) and sent to the receiver of the user. The assistance data used preferably consist of transmitter clock values associated with the carrier code sliding combination (Θ_eme) or with data sufficient for reconstructing said values. The transmitter clock values associated with the carrier code sliding combination (Θ_eme) can be reconstructed from iono-free transmitter clock values (h_eme) and clock biases (C′_eme), for example.

Claims

1-13. -13. (canceled)

14. A method of determining assistance data to facilitate the processing of radio-navigation signals from a set of radio-navigational satellites, each broadcasting at least a first radio-navigation signal on a first frequency and a second navigation signal on a second frequency distinct from the first, the method comprising the actions:

receiving code and phase measurements from the said radio-navigation signals recorded by receivers in a reference network;

said phase measurements having each an ambiguity that is an a priori unknown integer number of cycles;

resolving the ambiguities in the phase measurements on the first frequency in a manner consistent for all the satellites and reference receivers;

deducing a set of iono-free transmitter phase clock values arising from the consistent resolution of said ambiguities and a set of iono-free receiver phase clock values arising from the consistent resolution of said ambiguities;

calculating, for each satellite-reference receiver pair, a carrier code shift combination value from the code measurement and the phase measurement performed by the respective reference receiver for the respective satellite on the first frequency, and subtracting from this value a geometric contribution, a contribution of the iono-free receiver phase clock value and an iono-free transmitter phase clock value as well as a contribution of the resolved ambiguity of the phase measurement, so as to obtain a measurement residue;

separating, in a manner consistent for all the satellites and receivers of the network, each of the obtained measurement residues into a transmitter part and a receiver part, and

smoothing the transmitter part of the said measurement residues.

15. The method according to claim 14, wherein the iono-free transmitter clock values associated with the consistent resolution of the ambiguities as well as the smoothed transmitter parts of the said measurement residues are provided to receivers outside the network as assistance data.

16. The method according to claim 14, wherein the iono-free transmitter clock values associated with the consistent resolution of the ambiguities as well as the smoothed transmitter parts of the said measurement residues are provided to receivers outside the network as assistance data over a telecommunications channel.

17. The method according to claim 14, comprising, for each satellite of said set of satellites, the action of calculating a transmitter clock value associated with the carrier code shift combination as the sum of the iono-free transmitter clock value and the smoothed measurement residue.

18. The method according to claim 17, wherein said transmitter clock values associated with the carrier code shift combination are provided to receivers outside the network as assistance data.

19. The method according to claim 17, wherein said transmitter clock values associated with the carrier code shift combination are provided to receivers outside the network as assistance data over a telecommunications channel.

20. The method according to claim 14, wherein the smoothing of the transmission parts of the said measurement residues is performed each time by fitting a sine function with a period of 12 hours.

21. The method according to claim 14, wherein the first frequency is selected among 1575.42 MHz, 1227.6 MHz, 1176.45 MHz, 1207.14 MHz, 1278.75 MHz, 1561.098 MHz, 1589.742 MHz, 1207.14 MHz or 1268.52 MHz.

22. A computer program product comprising carrier means containing a computer program code configured to implement a method of determining assistance data to facilitate the processing of radio-navigation signals from a set of radio-navigational satellites, each broadcasting at least a first radio-navigation signal on a first frequency and a second navigation signal on a second frequency distinct from the first, computer program code comprising instructions implementing the actions:

receiving code and phase measurements from the said radio-navigation signals recorded by receivers in a reference network;

said phase measurements having each an ambiguity that is an a priori unknown integer number of cycles;

resolving the ambiguities in the phase measurements on the first frequency in a manner consistent for all the satellites and reference receivers;

deducing a set of iono-free transmitter phase clock values arising from the consistent resolution of said ambiguities and a set of iono-free receiver phase clock values arising from the consistent resolution of said ambiguities;

calculating, for each satellite-reference receiver pair, a carrier code shift combination value from the code measurement and the phase measurement performed by the respective reference receiver for the respective satellite on the first frequency, and subtracting from this value a geometric contribution, a contribution of the iono-free receiver phase clock value and an iono-free transmitter phase clock value as well as a contribution of the resolved ambiguity of the phase measurement, so as to obtain a measurement residue;

separating, in a manner consistent for all the satellites and receivers of the network, each of the obtained measurement residues into a transmitter part and a receiver part, and

smoothing the transmitter part of the said measurement residues.

23. A geopositioning method using radio-navigation signals from a set of satellites, each broadcasting at least a first radio-navigation signal on a first frequency and a second navigation signal on a second frequency distinct from the first, the method comprising, at the level of a radio-navigation signal receiver, the actions:

receiving, for each satellite of the said set and visible from the said receiver, at least the said first radio-navigation signal;

performing, for each visible satellite, the code measurements and the phase measurements of the first radio-navigation signal received, said phase measurements presenting an ambiguity of an a priori unknown integer number of cycles;

receiving a set of assistance data, wherein the set of assistance data comprises, for each satellite of the set of satellites, data sufficient for reconstructing a transmitter clock value associated with a carrier code shift combination, derived in a consistent manner for all the satellites and receivers of a reference network;

calculating, for each satellite, a carrier code shift combination value from the code measurement and the phase measurement of the first radio-navigation signal, and subtracting from said carrier code shift combination value the transmitter clock value associated with the carrier code shift combination, so as to obtain an unambiguous carrier code shift observable; and

determining the position of the receiver using the non-ambiguous carrier code shift observables.

24. The method according to claim 23, wherein the data sufficient for reconstructing the transmitter clock value associated with the carrier code shift combination comprise a satellite clock value associated with the carrier code shift combination.

26. The method according to claim 23, wherein the first frequency is selected among 1575.42 MHz, 1227.6 MHz, 1176.45 MHz, 1207.14 MHz, 1278.75 MHz, 1561.098 MHz, 1589.742 MHz, 1207.14 MHz or 1268.52 MHz.

27. A computer program product comprising carrier means containing a computer program code configured to implement a geopositioning method using radio-navigation signals from a set of satellites, each broadcasting at least a first radio-navigation signal on a first frequency and a second navigation signal on a second frequency distinct from the first, the computer program code comprising instructions implementing the actions:

receiving, for each satellite of the said set and visible from a receiver, at least the said first radio-navigation signal;

performing, for each visible satellite, the code measurements and the phase measurements of the first radio-navigation signal received, said phase measurements presenting an ambiguity of an a priori unknown integer number of cycles;

receiving a set of assistance data, wherein the set of assistance data comprises, for each satellite of the set of satellites, data sufficient for reconstructing a transmitter clock value associated with a carrier code shift combination, derived in a consistent manner for all the satellites and receivers of a reference network;

calculating, for each satellite, a carrier code shift combination value from the code measurement and the phase measurement of the first radio-navigation signal, and subtracting from said carrier code shift combination value the transmitter clock value associated with the carrier code shift combination, so as to obtain an unambiguous carrier code shift observable; and

determining a receiver position using the non-ambiguous carrier code shift observables.

28. A GNSS receiver configured to implement configured to implement a geopositioning method using radio-navigation signals from a set of satellites, each broadcasting at least a first radio-navigation signal on a first frequency and a second navigation signal on a second frequency distinct from the first, the GNSS receiver being configured to implement the actions:

receiving, for each satellite of the said set and visible from the GNSS receiver, at least the said first radio-navigation signal;

performing, for each visible satellite, the code measurements and the phase measurements of the first radio-navigation signal received, said phase measurements presenting an ambiguity of an a priori unknown integer number of cycles;

receiving a set of assistance data, wherein the set of assistance data comprises, for each satellite of the set of satellites, data sufficient for reconstructing a transmitter clock value associated with a carrier code shift combination, derived in a consistent manner for all the satellites and receivers of a reference network;

calculating, for each satellite, a carrier code shift combination value from the code measurement and the phase measurement of the first radio-navigation signal, and subtracting from said carrier code shift combination value the transmitter clock value associated with the carrier code shift combination, so as to obtain an unambiguous carrier code shift observable; and

determining a GNSS receiver position using the non-ambiguous carrier code shift observables.