Precise low-latency GNSS satellite clock estimation

• US 10,191,157 B2
• Filed: 09/06/2016
• Issued: 01/29/2019
• Est. Priority Date: 03/18/2016
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Dai, Liwen L., Kuntz, Sonia U., Zhang, Yujie, Chen, Yiqun
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US15/257,092
• Publication Number:
  US 20170269222A1
• Time in Patent Office: 875 Days
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/072 Ionosphere corrections
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

A wide-lane ambiguity and a respective satellite wide-lane bias are determined for the collected phase measurements for each satellite for assistance in narrow-lane ambiguity resolution. Satellite correction data is determined for each satellite in an orbit solution based on the collected raw phase and code measurements and determined orbital narrow-lane ambiguity and respective orbital satellite narrow-lane bias. A slow satellite clock correction is determined based on the satellite orbital correction data, the collected raw phase and code measurements, and clock narrow-lane ambiguity and respective satellite narrow-lane bias. A low latency clock module or data processor determines lower-latency satellite clock correction data or delta clock adjustment to the slow satellite clock based on freshly or recently updated measurements of the collected raw phase measurements that are more current than a plurality of previous measurements of the collected raw phase measurements used for the slow satellite clock correction to provide lower-latency clock correction data.

Claims

1. A method for providing a global satellite differential correction signal, the method comprising:

collecting raw carrier phase measurements and pseudorange code measurements from a plurality of reference receivers at known corresponding locations that receive satellite signals from a Global Navigation Satellite System (GNSS);

determining, by a measurement pre-processing module, a wide-lane ambiguity and a respective satellite wide-lane bias for the collected raw carrier phase measurements and code measurements for each satellite;

determining an orbital narrow-lane ambiguity and an orbital satellite narrow-lane bias for the collected phase measurements for each satellite in an orbit solution based on the collected raw carrier phase and code measurements, consistent with the determined wide-lane ambiguity and the respective satellite wide-lane bias;

determining satellite orbital correction data for an orbit solution based on the collected raw carrier phase and code measurements and the determined orbital narrow-lane ambiguity and orbital satellite narrow-lane bias;

determining a clock narrow-lane ambiguity and a respective clock satellite narrow-lane bias for the collected phase measurements for each satellite in a slow clock solution based on the collected raw phase and code measurements, consistent with the determined wide-lane ambiguity and the respective satellite wide-lane bias;

determining, by a clock solution module, a slow satellite clock correction based on the satellite orbital correction data, the collected raw carrier phase and code measurements and the determined clock narrow-lane ambiguity and clock satellite narrow-lane bias;

determining lower-latency satellite clock correction data or delta clock adjustment to the slow satellite clock based on freshly or recently updated measurements of the collected raw phase measurements that are more current than a plurality of previous measurements of the collected raw phase measurements used for the slow satellite clock correction to provide lower-latency clock correction data; and

incorporating the satellite wide-lane bias, the satellite orbital correction data, the satellite narrow-lane bias from the slow clock solution and the low latency clock correction data into the correction data, encoded on the global satellite differential correction signal, with global validity for the GNSS transmission to one or more mobile receivers.

2. The method according to claim 1 further comprising:

transmitting the correction data, comprising the lower-latency satellite clock correction data, via a correction data message to one or more mobile receivers.

3. The method according to claim 1 further comprising:

transmitting, via a satellite communications channel or a wireless communications channel, the lower-latency satellite correction data that comprises satellite orbit, clock, satellite wide-lane bias, satellite narrow lane bias and quality signals for each satellite via a correction data message.

4. The method according to claim 1 wherein the latency can be measured based on time difference between an earlier epoch associated with a collection of phase measurements of satellite signals at one or more reference receivers and receipt of processed measurements at a later epoch in mobile rover receiver.

5. The method according to claim 1 further comprising determining, by the slow clock module a tropospheric delay bias and gradients per reference receiver to facilitate determination of a refraction correction for the clock narrow lane ambiguity and respective narrow lane bias.

6. The method according to claim 1 wherein the determining the lower-latency satellite clock correction data or delta clock adjustment comprises estimating the delta clock adjustment or relative clock error at the fast update rate using double-difference techniques between measurement times or epochs of the phase measurements for a reference receiver.

7. The method according to claim 6 further comprising:

selecting a highest elevation satellite without cycle slips as the reference satellites for the reference receiver at each site.

8. The method according to claim 6 wherein the fast update rate comprises a rate of approximately 1 Hertz or greater.

9. The method according to claim 1 wherein the incorporating further comprises integrating the fast clock solution and the slow clock solution over an integration period to provide an absolute satellite clock estimate.

10. The method according to claim 1 wherein the slow clock solution is provided with a moderate latency comprising the longer GNSS raw data collection time of approximately 6 seconds to approximately 10 seconds for more GNSS raw data and a few seconds of data processing time for a complicated slow clock solution.

11. The method according to claim 1 wherein the lower-latency satellite clock correction data is provided with a lower latency, than the moderate latency of the slow clock solution, including a shorter GNSS raw data collection time of approximately 1 second to approximately 2 seconds.

12. The method according to claim 1 further comprising using a troposphere estimation from the slow clock solution in the lower-latency satellite clock correction data.

13. The method according to claim 1 further comprising using orbital correction data from an orbit solution in the slow clock solution and the lower-latency satellite clock correction data.

14. The method according to claim 1 further comprising using a delta-clock from a lower-latency satellite clock solution associated with a update interval of the slow clock solution such as approximately 30 seconds to approximately 60 seconds predict a satellite clock dynamic the in the slow clock solution, the accumulated delta-clock or change from a fast clock solution associated with an update interval of the orbit solution such as approximately 300 seconds to predict a satellite clock dynamic in the orbit solution.

15. The method according to claim 1 wherein the lower-latency correction comprises a change in a satellite clock correction using GNSS carrier phase data only.

16. The method according to claim 1 wherein the moderate-latency data estimates including absolute satellite clocks, tropospheric bias, satellite narrow-lane bias and narrow-lane ambiguity solution.

17. The method according to claim 1 wherein correction data comprises the satellite orbital correction data, the lower-latency satellite clock correction data, the satellite wide-lane bias data, the satellite narrow-lane bias data, and satellite quality indicators of the lower-latency clock and narrow-lane bias.

18. A method for providing a global satellite differential correction signal, the method comprising:

collecting raw phase measurements and pseudorange measurements from a plurality of reference receivers at known corresponding locations that receive satellite signals from a Global Navigation Satellite System (GNSS);

determining, by a measurement pre-processing module, a fixed integer wide-lane ambiguity and a respective satellite wide-lane bias for the collected raw carrier phase measurements and pseudorange measurements for each satellite;

determining, by an orbit solution module, an orbital narrow-lane ambiguity and an orbital satellite narrow-lane bias for the collected phase measurements for each satellite in an orbit solution based on the collected raw carrier phase and psuedorange measurements, consistent with the determined wide-lane ambiguity and the respective satellite wide-lane bias;

determining satellite orbital correction data at an orbit correction rate for the orbit solution based on the collected raw carrier phase and psuedorange measurements and the determined orbital narrow-lane ambiguity and orbital satellite narrow-lane bias;

determining a clock narrow-lane ambiguity and a respective clock satellite narrow-lane bias for the collected phase measurements for each satellite in a slow clock solution based on the collected raw phase and pseudorange measurements, consistent with the determined wide-lane ambiguity and the respective satellite wide-lane bias;

determining, by a clock solution module, a slow satellite clock correction at a slow update rate based on the satellite orbital correction data, the collected raw phase and pseudorange measurements and the determined clock narrow-lane ambiguity and clock satellite narrow-lane bias;

determining lower-latency satellite clock correction data or delta clock adjustment to the slow satellite clock at a fast update rate based on freshly or recently updated measurements of the collected raw phase measurements that are more current than a plurality of previous measurements of the collected raw phase measurements used for the slow satellite clock correction to provide lower-latency clock correction data; and

incorporating the satellite orbital correction data, the low latency clock correction data, the satellite wide-lane bias and the satellite narrow-lane bias into the correction data, encoded on the global satellite differential correction signal, with global validity for the GNSS for transmission to one or more mobile receivers that operate in a precise point positioning (PPP) mode.

19. The method according to claim 18 wherein the orbit rate is less than the slow update rate.

20. The method according to claim 18 further comprising:

applying an orbit zero-difference filter to facilitate the estimation of the orbit narrow-lane ambiguity and respective narrow-lane satellite bias at the orbit update rate based on the collected raw phase measurements.

21. The method according to claim 18 wherein the fast update rate is greater than the slow update rate or the orbit rate.

22. The method according to claim 18 further comprising:

applying an clock zero-difference filter to facilitate the estimation of the orbit narrow-lane ambiguity and respective narrow-lane satellite bias at the slow update rate based on the collected raw phase measurements.