Moving reference receiver for RTK navigation

• US 20060017611A1
• Filed: 07/26/2004
• Published: 01/26/2006
• Est. Priority Date: 07/26/2004
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Navcom Technology, Inc. (Deere & Company)
• Inventors: Hatch, Ronald R., Sharpe, Richard T.
• Granted Patent: US 7,248,211 B2
• Time in Patent Office: Days
• US Class Current: 342/357.310
• 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
• CPC Class Codes: G01S 5/0045 Transmission from base station to mobile station G01S5/009 takes precedence

Abstract

A method and system are provided to determine a relative position vector between primary receiver associated with a reference station and secondary receiver associated with a user. The method and system determine a position of the reference station at the reference station according to signals received thereat from a plurality of satellites, determine a position of the user receiver at the user based on measurements obtained thereat and on error corrections computed at the reference station, and compute the relative position vector by differencing the position of the reference station and the position of the user.

Claims

1. A method for navigating a first object with reference to a second object, comprising:

obtaining a set of carrier-phase measurements according to signals received at the first object from a plurality of satellites;

correcting the set of carrier-phase measurements using corrections computed at the second object; and

determining a position correction for the first object using the corrected set of carrier-phase measurements.

2. The method of claim 1 further comprising adding the position correction to a computed position of the first object to obtain a corrected position of the first object.

3. The method of claim 2 further comprising computing position updates for the first object using successive changes in the carrier-phase measurements obtained at the first object from the plurality of satellites.

4. The method of claim 3 wherein the changes in the carrier-phase measurements are refraction-corrected.

5. The method of claim 1 wherein determining the position correction comprises resolving integer ambiguities in the carrier-phase measurements.

6. The method of claim 1 wherein the second object is a moving object.

7. The method of claim 6 further comprising:

receiving from the second object a computed position of the second object; and

computing a vector difference between a computed position of the first object and the computed position of the second object.

8. A method for a reference station to provide measurement corrections to at least one navigating object, comprising:

obtaining code and carrier-phase measurements at the reference station according to signals from a plurality of satellites;

forming carrier-smoothed code measurements corresponding to the code and carrier-phase measurements;

determining a position of the reference station using the carrier-smoothed code measurements;

computing a theoretical range between the reference station and each of the plurality of satellites using the position of the reference station;

computing measurement corrections using the theoretical range;

transmitting the measurement corrections to at least one navigating object.

9. The method of claim 8 wherein the code and carrier-phase measurements include measurement corrections provided by a wide-area or global navigation system.

10. The method of claim 8 wherein the carrier-smoothed code measurements include measurement corrections provided by a wide-area or global navigation system.

11. In a satellite navigation system comprising a moving reference station, a method for determining a position of a user of the satellite navigation system relative to a position of the moving reference station, comprising:

determining the position of the moving reference station according to signals received at the moving reference station from a plurality of satellites;

determining the position of the user based on measurements obtained at the user according to signals received by the user from the plurality of satellites and on corrections to the measurements received from the moving reference station; and

computing a vector difference between the position of the user and the position of the moving reference station.

12. The method of claim 11 wherein the vector difference is computed at the user.

13. The method of claim 11 wherein the vector difference is computed at the moving reference station.

14. The method of claim 11 wherein the vector difference is computed at a separate date processing system that receives the position of the user from the user and the position of the moving reference station from the moving reference station.

15. The method of claim 11 wherein determining the position of the reference station comprises determining a change in the position of the reference station based on changes in carrier-phase measurements obtained at the reference station according to signals from the plurality of satellites.

16. The method of claim 11 wherein determining the position of the user comprises determining a change in the position of the user based on changes in carrier-phase measurements obtained at the user according to signals from the plurality of satellites.

17. A satellite navigation system, comprising:

a reference subsystem configured to;

obtain first satellite range measurements according to signals received by the reference subsystem from a plurality of satellites;

determine a reference position associated with the reference subsystem according to the first satellite range measurements; and

compute error corrections to the first satellite range measurements, the error corrections including error corrections to carrier-phase measurements; and

a user subsystem configured to;

receive the error corrections from the reference subsystem;

obtain second satellite range measurements according to signals received by the user subsystem from the plurality of satellites, the second satellite range measurements including carrier-phase measurements;

adjusting the second satellite range measurements using the error corrections; and

determine a user position based on the adjusted second satellite range measurements; and

wherein the satellite navigation system determines a relative position vector by differencing the user position and the reference position.

18. A computer-readable medium storing therein computer readable instructions that when executed by a processor cause the processor to perform a method for navigating a first object with reference to a second object, the instructions comprising:

instructions for obtaining a set of measurements according to signals received at the first object from a plurality of satellites;

instructions for correcting the set of measurements using corrections computed at the second object according to signals received at the second object from the plurality of satellites; and

instructions for determining a position correction for the first object using the corrected set of measurements.

19. The computer-readable medium of claim 18 further comprising instructions for adding the position correction to a computed position of the first object to obtain a corrected position of the first object.

20. The computer-readable medium of claim 19 further comprising instructions for computing position updates for the first object using successive changes in a set of carrier-phase measurements obtained at the first object from the plurality of satellites.

21. A computer-readable medium storing therein computer readable instructions that when executed by a processor cause the processor to perform method for a reference station to provide measurement corrections to at least one navigating object, the instructions comprising:

instructions for obtaining code and carrier-phase measurements at the reference station according to signals from a plurality of satellites;

instructions for forming carrier-smoothed code measurements corresponding to the code and carrier-phase measurements;

instructions for determining a position of the reference station using the carrier-smoothed code measurements;

instructions for computing a theoretical range between the reference station and each of the plurality of satellites using the position of the reference station;

instructions for computing measurement corrections using the theoretical range;

instructions for transmitting the measurement corrections to the at least one navigating object.