Position determination with reference data outage

• US 7,576,690 B2
• Filed: 12/13/2007
• Issued: 08/18/2009
• Est. Priority Date: 10/29/2007
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Vollath, Ulrich
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Mull; Fred H
• Application Number:
  US12/002,086
• Publication Number:
  US 20090109090A1
• Time in Patent Office: 614 Days
• Field of Search: 34235707-3571, 342/357.03, 342/357.12
• US Class Current: 342/357.24
• CPC Class Codes: G01S 19/05 providing aiding data
• 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 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry

Abstract

Position determination at a rover station on the basis of positioning signals from a plurality of positioning satellites. During normal operation a position of the rover station is determined on the basis of the positioning signal from the positioning satellites and reference data received via a separate connection from a reference station. Upon detecting an outage of the reference data from the reference station, error data at least including satellite clock drifts is obtained from error data transmitter and applied in the determination process in order to eliminate positioning errors introduced by satellite clock drifts that cannot be compensated on the basis of the reference data due to the outage.

Claims

1. A rover station for determining a position, the rover station including:

a positioning signal receiver to receive positioning signals from each of a plurality of positioning satellites;

a reference data receiver to receive reference data from at least one reference station;

a positioning unit to determine a position of the rover station for a first instance in time based on positioning signals for the first instance in time and the reference data for the first instance in time;

an outage detection unit to detect an outage of the reference data from the at least one reference station; and

an error data receiver to receive for each of the satellite clocks error data specifying a satellite clock drift;

wherein the positioning unit is adapted to determine the position of the rover station for a second instance in time based on positioning signals for the second instance in time, the reference data for the first instance in time and the satellite clocks error data at least for the second instance in time.

2. The rover station of claim 1, wherein the positioning unit, for determining the position of the rover station at the second instance in time, is adapted to:

determine reference data for the second instance in time based on the reference data for the first instance in time and the satellite clocks error data; and

determine the position of the rover station for the second instance in time based on the estimated reference data and the positioning signals for the second instance in time.

3. The rover station of claim 1, wherein the positioning unit, for determining the position of the rover station at the second instance in time, is adapted to:

correct the positioning signals received from the positioning satellites for the second instance in time based on the satellite clocks error data; and

determine the position for the second instance in time based on the corrected positioning signals for the second instance in time and the reference data for the first instance in time.

4. The rover station of claim 1, wherein the positioning unit, for determining the position of the rover station at the second instance in time, is adapted to:

obtain a position vector of the rover station for the first instance in time;

obtain a first position difference vector using a delta phase method based on the positioning signals and the reference data of the first instance in time, and the positioning signals of the second instance in time and the satellite clocks error data; and

add the first position difference vector to the position vector of the first instance in time.

5. The rover station of claim 4, wherein the positioning unit, for determining the position of the rover station at the second instance in time, is adapted to:

obtain a second position difference vector using the delta phase method based on positioning signals and reference data of a third instance in time preceding the first instance in time, and the positioning signals and the reference data of the first instance in time; and

add the second position difference vector to a position vector of the third instance in time.

6. The rover station of claim 1, wherein the reference data includes at least one of:

range corrections for each of the plurality of satellites; and

raw observations at the at least one reference station.

7. The rover station of claim 1, wherein the error data receiver is adapted to receive the clock error data from at least one of:

the plurality of positioning satellites;

an alternate satellite source; and

a ground based station via wireline or wireless communications.

8. The rover station of claim 1, wherein the error data receiver is adapted to receive the clock error data at predetermined time intervals over a low bandwidth link.

9. The rover station of claim 1, wherein the positioning unit is arranged to obtain at least one of a time dependent satellite orbit error and troposphere error for each of the satellites and to correct the position of the rover station based on the satellite orbit and troposphere errors.

10. The rover station of claim 1, wherein the positioning unit is arranged to obtain a time dependent relativistic clock error for each of the satellites and to correct the position of the rover station based thereon.

11. A position determining method, the method including:

receiving positioning signals from each of a plurality of positioning satellites;

receiving reference data from at least one reference station;

determining a position of the rover station for a first instance in time based on positioning signals for the first instance in time and the reference data for the first instance in time;

detecting an outage of the reference data from the at least one reference station;

obtaining for each of the satellite clocks error data specifying a satellite clock drift; and

determining the position of the rover station for a second instance in time based on positioning signals for the second instance in time, the reference data for the first instance in time and the satellite clocks error data at least for the second instance in time.

12. The method of claim 11, wherein the position of the rover station for the second instance in time is determined by:

determining reference data for the second instance in time based on the reference data for the first instance in time and the satellite clocks error data; and

determining the position of the rover station for the second instance in time based on the estimated reference data and the positioning signals for the second instance in time.

13. The method of claim 11, wherein the position of the rover station for the second instance in time is determined by:

correcting the positioning signals received from the positioning satellites for the second instance in time based on the satellite clocks error data; and

determining the position for the second instance in time based on the corrected positioning signals for the second instance in time and the reference data for the first instance in time.

14. The method of claim 11, wherein the position of the rover station for the second instance in time is determined by:

obtaining a position vector of the rover station for the first instance in time;

obtaining a first position difference vector using a delta phase method based on the positioning signals and the reference data of the first instance in time, and the positioning signals of the second instance in time and the satellite clocks error data; and

adding the first position difference vector to the position vector of the first instance in time.

15. The method of claim 14, wherein obtaining the position vector of the rover station for the first instance in time includes:

obtaining a second position difference vector using the delta phase method based on positioning signals and reference data of a third instance in time preceding the first instance in time, and the positioning signals and the reference data of the first instance in time; and

adding the second position difference vector to a position vector of the third instance in time.

16. The method of claim 11, wherein the reference data includes at least one of:

range corrections for each of the plurality of satellites, and

raw observations at the at least one reference station.

17. The method of claim 11, wherein the clock error data is received from at least one of:

the plurality of positioning satellites;

another satellite; and

a ground based station via wireline or wireless communications.

18. The method of claim 11, wherein the clock error data is obtained at predetermined time intervals over a low bandwidth link.

19. The method of claim 11, including obtaining at least one of a time dependent satellite orbit error and troposphere error for each of the satellites and correcting the position of the rover station based on the satellite orbit and troposphere errors.

20. The method of claim 11, including computing a time dependent relativistic clock error for each of the satellites and correcting the position of the rover station based thereon.

21. The method of claim 11, further including embodying a program of instructions on a computer readable medium, where the program is to make data processing means to execute the method of claim 11.

22. The method of claim 21, further comprising:

providing a computer program product comprising the computer readable medium according to claim 21.