Rapid recovery of precise position after temporary signal loss

• US 10,422,885 B2
• Filed: 10/07/2016
• Issued: 09/24/2019
• Est. Priority Date: 03/18/2016
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Dai, Liwen L., Wang, Min, Hwang, Soon Sik
• Primary Examiner(s): McGue, Frank J
• Application Number:
  US15/288,371
• Publication Number:
  US 20170269231A1
• Time in Patent Office: 1,082 Days
• Field of Search: 34235727
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

A real-time kinematic (RTK) filter uses the backup data to estimate a relative position vector between the mobile receiver at the first measurement time and the mobile receiver at the second measurement time and to provide recovery data associated with a satellite-differenced double-difference estimation for the mobile receiver between the first measurement time and the second measurement time. A navigation positioning estimator can apply the relative position vector, the backup data, the recovery data from the RTK filter, and received correction data with precise clock and orbit information on the satellite signals, as inputs, constraints, or both for convergence or resolution of wide-lane and narrow-lane ambiguities, and determination of a precise position, in accordance with a precise positioning algorithm.

Claims

1. A method for providing or rapidly recovering an estimated position of a mobile receiver, the method comprising execution of the following steps at or by the mobile receiver:

receiving a set of one or more carrier satellite signals and a correction signal encoded with correction data that is related to the one or more carrier satellite signals;

measuring the carrier phase of one or more received satellite signals a first measurement time;

estimating a wide-lane ambiguity and narrow-lane ambiguity in the measured carrier phase of the one or more received satellite signals for the first measurement time and estimating tropospheric bias for one or more of the carrier satellite signals;

storing, at regular time intervals for the first measurement time, backup data comprising a set of the following post-convergence or resolved values;

the estimated wide-lane ambiguities, the estimated narrow-lane ambiguities, the estimated tropospheric delay bias, raw measured carrier phase of the received satellite signals, and corresponding estimated receiver positions;

detecting a loss of lock on the measured carrier phase associated with loss or lack of reception of one or more of the carrier signals for a loss time period;

after the detected loss of lock once at least some carrier phase signals are reacquired, measuring the carrier phase of one or more received satellite signals at a second measurement time;

retrieving or reading the backup data and applying the backup data to a real-time kinematic (RTK) filter to provide a relative position vector between the mobile receiver at the first measurement time and the mobile receiver at the second measurement time and to provide recovery data associated with a satellite-differenced double-difference estimation for the mobile receiver between the first measurement time and the second measurement time;

applying the relative position vector, the backup data, the recovery data from the RTK filter, and the correction data with precise clock and orbit information on the satellite signals, as inputs, constraints, or both for convergence or resolution of one or more predictive filters on wide-lane and narrow-lane ambiguities in accordance with a precise positioning algorithm;

estimating a precise position of the mobile receiver based on the resolved narrow-lane ambiguities and wide-lane ambiguities that are in a converged state or fixed state, where the above steps are executable or implemented by a data processor of an electronic data processing system of the mobile receiver;

wherein the mobile receiver position at the first measurement time comprises a precise point positioning position of the mobile receiver at the first measurement time, and wherein the recovery data includes one or more of the following;

RTK double-difference (DD) wide-lane integer ambiguity, ∇

Δ

N_WL^ij(RTK);

RTK fixed refraction-corrected (RC) double-difference (DD) ambiguity, ∇

Δ

N_RC^ij(RTK); and

the relative position between the reference receiver and the mobile receiver, and the variance/co-variance of the relative position.

2. The method according to claim 1 wherein the backup data further comprises one or more of the following estimated at the mobile receiver at the first measurement time:

fixed wide-lane ambiguities that are fixed to integer ambiguity values, estimated refraction-corrected ambiguities, raw measurements, or tropospheric delay at zenith direction including an a priori model.

3. The method according to claim 1 wherein the recovery data comprises L1/L2 fixed double-difference (DD) ambiguities from the RTK filter at the mobile receiver based on raw phase measurements at the mobile receiver at the first measurement time and the second measurement time for a pair of satellites.

4. The method according to claim 1 wherein applying the backup data to real-time kinematic (RTK) filter further comprises:

estimating, by the RTK filter, a relative position or the relative position vector of mobile receiver between the first measurement time and the second measurement time based on a set of real-time kinematic (RTK) algorithms to resolve the L1/L2 double-differenced (DD) fixed integer values (N₁, N₂) at an L1 frequency of the carrier satellite signals and a pair of satellites per Global Navigation Satellite System (GNSS) system and between an L2 frequency of the carrier satellite signals and the same pair of satellites per GNSS system.

5. The method according to claim 1 wherein the resolved values of the wide-lane ambiguities comprise pulled-in or converged wide-lane ambiguities and wherein the resolved values of the narrow-lane ambiguities comprise pulled-in or converged narrow-lane ambiguities from one or more Global Navigation Satellite System (GNSS) satellites'"'"' carrier signals at the mobile receiver.

6. The method according to claim 1 wherein estimating the precise position of the mobile receiver further comprises estimating refraction-corrected (RC) ambiguities to the converged state and tropospheric bias for the mobile receiver based on the backup data and the correction data.

7. The method according to claim 1 further comprising:

at the mobile receiver, estimating of wide-lane (WL) ambiguities, by a predictive filter or wide-lane filter, is based on a LAMBDA or modified LAMBDA procedure to prepare for determination of the narrow-lane ambiguities in integer form.

8. The method according to claim 1 wherein further comprising:

determining whether a reacquisition or detected restoration of the reception of the carrier phase signals is within a maximum recovery time period prior to applying the real-time kinematic (RTK) filter to resolve ambiguities associated with double-difference carrier phase measurements.

9. The method according to claim 1 wherein, at the mobile receiver at the first measurement time, refraction-corrected ambiguities, (N_RC) for satellite j are determined based on a Kalman filter in accordance with the following equations after resolving the wide-lane ambiguities:

10. The method according to claim 1 wherein the resolved double-differenced (DD) L1/L2 integer ambiguities are determined in accordance with the following equations:

11. The method according claim 10 wherein after resolution of the double-difference L1/L2 ambiguities in claim 10, RTK wide-lane ambiguities are determined in accordance with the following equation:

∇

Δ

N_WL^ij(RTK)=∇

Δ

N₁^ij−

∇

Δ

N₂^ij

where;

∇

Δ

N_WL^ij(RTK) is the RTK double-difference wide-lane ambiguity for satellites i and j with respect to the mobile receiver at the first measurement time and the second measurement time;

∇

Δ

N₁^ij is the double-difference L1 wide-lane ambiguity for satellites i and j with respect to the mobile receiver at the first measurement time and the second measurement time; and

∇

Δ

N₂^ij is the double-difference L2 wide-lane ambiguity for satellites i and j with respect to the mobile receiver at the first measurement time and the second measurement time.

12. The method according to claim 1 further comprising providing aiding data comprising refraction-corrected ambiguity between satellite i and j can be derived in accordance with the following equation:

13. The method according to claim 1 wherein the following parameters of double-difference (DD) wide-lane integer ambiguity, the fixed refraction-corrected ambiguity, the relative position Δ

X and their variance/co-variance are used as additional constraints to speed up a filter convergence process of the one or more predictive filters at the mobile receiver.

14. The method according to claim 1 further comprising:

using RTK double-difference wide-lane ambiguities ∇

Δ

N_WL^ij(RTK) for satellites i and j (with respect to the mobile receiver at the first measurement time and the second measurement time) and the single-difference wide lane ambiguity, ∇

N_WL^ij(t₁), at the mobile receiver at the first measurement time to derive or estimate the respective single-difference ambiguities, ∇

N_WL^ij(t₂), at the mobile receiver at a second measurement time in accordance with the following equation;

∇

N_WL^ij(t₂)=∇

Δ

N_WL^ij(RTK)+∇

N_WL^ij(t₁).

15. The method according to claim 1 further comprising:

using an estimated position X(t₂) of the mobile receiver and a corresponding covariance matrix Q_XYZ(t₂) for the estimated position of the mobile receiver at the second measurement time as virtual measurements or constraints to be applied to a narrow-lane filter as the one or more predictive filters in accordance with the following equations;

X(t₂)=Δ

X_RTK−

X(t₁) and

Q_XYZ(t₂)=Q<sub>Δ

XYZ(RTK)</sub>±

Q_XYZ(t₁)

where;

Δ

X_RTK is a relative change in position of the mobile receiver that is observed by the RTK filter between the first measurement time, t₁, and the second measurement time, t₂;

X(t₁) is the estimated position of the mobile receiver at the first measurement time, t₁;

Q<sub>Δ

XYZ(RTK)</sub> is the change in the covariance matrix associated with the relative change in position Δ

X_RTK; and

Q_XYZ (t₁) is the covariance matrix for the estimated position of the mobile receiver at the first measurement time.

16. The method according to claim 1 further comprising:

using previously estimated troposphere bias T(t₂) and corresponding covariance matrix

17. The method according to claim 1 further comprising:

using RTK double-difference refection-corrected ambiguities ∇

Δ

N_RC^ij(RTK) for satellites i and j (with respect to the mobile receiver at the first measurement time and the second measurement time) and the single-difference refraction-corrected ambiguity, ∇

Δ

N_RC^ij(t₁), at the mobile receiver at the first measurement time to derive or estimate the respective single-difference refection-corrected ambiguities, ∇

Δ

N_RC^ij(t₂), at the mobile receiver at a second measurement time in accordance with the following equation;

∇

N_RC^ij(t₂)=∇

Δ

N_RC^ij(RTK)+∇

N_RC^ij(t₁).

18. A mobile receiver for quickly determining a precise position based on correction data received from a correction data source, the mobile receiver comprising:

a receiver module for receiving a set of one or more satellite signals;

a measurement module for measuring the carrier phase of one or more received satellite signals for a first measurement time;

a correction wireless device for receiving a correction signal related to the set of one or more satellite signals;

an estimator for estimating a wide-lane ambiguity and narrow-lane ambiguity in the measured carrier phase of the one or more received satellite signals for the first measurement time and estimating tropospheric bias for one or more of the carrier satellite signals;

a data storage device for storing, at regular time intervals for the first measurement time, backup data comprising a set of the following post-convergence or resolved values;

the estimated wide-lane ambiguities, the estimated narrow-lane ambiguities, the estimated tropospheric delay bias, raw measured carrier phase of the received satellite signals, and one or more corresponding estimated receiver positions;

a detector for detecting a loss of lock on the measured carrier phase associated with loss or lack of reception of one or more of the carrier satellite signals for a loss time period;

after the detected loss of lock once at least some carrier phase signals are reacquired, the measurement module adapted to measure the carrier phase of one or more received satellite signals at a second measurement time;

a real-time kinematic (RTK) filter for using the backup data to estimate a relative position vector between the mobile receiver at the first measurement time and the mobile receiver at the second measurement time and to provide recovery data associated with a satellite-differenced double-difference estimation for the mobile receiver between the first measurement time and the second measurement time;

a navigation positioning estimator for applying the relative position vector, the backup data, the recovery data from the RTK filter, and the correction data with precise clock and orbit information on the satellite signals, as inputs, constraints, or both for convergence or resolution of wide-lane and narrow-lane ambiguities in accordance with a precise positioning algorithm; and

the navigation positioning estimator adapted to estimate a precise position of the mobile receiver based on the resolved narrow-lane ambiguities and wide-lane ambiguities that are in a converged state or fixed state, where the above is implemented by a data processor of an electronic data processing system of the mobile receiver;

wherein the mobile receiver position at the first measurement time comprises a precise point positioning position of the mobile receiver at the first measurement time, and wherein the recovery data includes one or more of the following;

RTK double-difference (DD) wide-lane integer ambiguity, ∇

Δ

_WL^ij (RTK);

RTK fixed refraction-corrected (RC) double-difference (DD) ambiguity, ∇

Δ

_RC^ij (RTK); and

the relative position between the reference receiver and the mobile receiver; and

the variance/co-variance of the relative position.

19. The mobile receiver according to claim 18 wherein the correction wireless device comprises a satellite receiver for receiving the correction signals in the L-band.

20. The mobile receiver according to claim 18 wherein the one or more estimated receiver positions comprise a precise point positioning reference position of the mobile receiver that is stationary or mobile at the first measurement time.

21. The mobile receiver according to claim 18 wherein the backup data further comprises one or more of the following estimated at the reference receiver:

resolved wide-lane ambiguities, estimated refraction-corrected ambiguities, raw measurements, and tropospheric delay at zenith direction associated with an a priori model.

22. The mobile receiver according to claim 18 wherein the recovery data comprises the L1/L2 fixed DD ambiguities from the RTK filter at the mobile receiver.

23. The mobile receiver according to claim 18 wherein the real-time kinematic (RTK) filter is adapted to estimate a relative position or relative position vector between a mobile receiver at the first measurement time and the second measurement time based on a set of real-time kinematic (RTK) algorithms to resolve the L1/L2 double-differenced (DD) fixed integer values (N₁, N₂) at an L1 frequency of the carrier satellite signals and a pair of satellites per Global Navigation Satellite System (GNSS) system and between an L2 frequency of the carrier satellite signals and the same pair of satellites per GNSS system.

24. An electronic data processing system for providing rapid position recovery of a rover navigation receiver after partial or full loss of received satellite signals, the system comprising:

a receiver module for receiving a set of one or more satellite signals;

a correction wireless device for receiving a correction signal related to the set of one or more satellite signals;

a measurement module for measuring the carrier phase of each one of the satellite signals in the set with respect to a local reference carrier signal;

an estimation module for estimating a wide-lane ambiguity and narrow-lane ambiguity in the measured carrier phase and tropospheric bias for each carrier signal in the set;

a data storage device for storing, at regular time intervals, backup data comprising post-convergence values of the estimated wide-lane ambiguity, the estimated narrow-lane ambiguity, raw code measurements and raw carrier phase measurements, the tropospheric bias and a corresponding reference position for a first measurement time;

a detector for detecting a loss of lock on the measured carrier phase associated with loss or lack of reception of one or more of the satellite signals for a loss time period; and

upon the detected loss of lock after some carrier phase signals are reacquired, a recovery module for recovering an accurate current position estimate, the tropospheric bias, the current wide-lane ambiguity, the current narrow-lane ambiguity based on the stored backup data and observed measurements of the carrier phase of the one or more received satellite signals at a second measurement time to estimate a relative position vector between the mobile receiver at the first measurement time and the mobile receiver at the second measurement time.

25. The electronic data processing system according to claim 24 wherein the recovery module is arranged to process a double-differenced observable for each satellite for the first measurement time, at a last first epoch, prior to the loss of lock and for the second measurement time, at a current epoch during a recovery of the accurate position estimate to precisely estimate the relative position estimate with respect to the last stored reference position.

26. The data processing system according to claim 25 wherein the double-differenced observable comprises carrier phase measurements for L1 frequency or L2 frequency of the received satellite signals, or code phase measurements for L1 frequency or L2 frequency of received satellite signals.

27. The data processing system according to claim 24 wherein the recovery module is arranged to conduct ambiguity resolution to recover wide-lane ambiguity changes and narrow-lane ambiguity changes during a re-convergence time period on the fixed L1 and L2 ambiguities in a real-time kinematic filter.