Method and system for estimating position with bias compensation

Patent metadata

Field	Value
Publication number	US-9599721-B2
Application number	US-201213715032-A
Country	US
Kind code	B2
Filing date	Dec 14, 2012
Priority date	Feb 26, 2010
Publication date	Mar 21, 2017
Grant date	Mar 21, 2017

Abstract

A primary phase measurement device measures a first carrier phase and a second carrier phase of carrier signals received by the location-determining receiver. A secondary phase measurement device measures the third carrier phase and the fourth carrier phase of other carrier signals. A real time kinematic engine estimates a first integer ambiguity set associated with the measured first carrier phase and a second integer ambiguity set associated with the measured second carrier phase. The real time kinematic engine estimates a third ambiguity set associated with the measured third carrier phase and a fourth ambiguity set associated with the measured fourth carrier phase. A compensator is capable of compensating for the inter-channel bias in at least one of the third ambiguity set and the fourth ambiguity set by modeling a predictive filter in accordance with various inputs or states of the filter estimated by an estimator.

First claim

The following is claimed:

1. A method for estimating the position of an object or vehicle by a location-determining receiver associated with the object or vehicle, the method comprising:
measuring, by a primary phase measurement device of the receiver, a first carrier phase of each first carrier signal of a plurality of first carrier signals and a second carrier phase of each second carrier signal of a plurality of second carrier signals received by the location-determining receiver, each first carrier signal of the plurality of first carrier signals received at substantially the same frequency as others of the first carrier signals from two or more primary satellites, each second carrier signal of the plurality of second carrier signals received at substantially the same frequency as others of the second carrier signals from two or more primary satellites;
measuring, by a secondary phase measurement device of the receiver, a third carrier phase of each third carrier signal of a plurality of third carrier signals and a fourth carrier phase of each fourth carrier signal of a plurality of fourth carrier signals received by the location-determining receiver, each third carrier signal of the plurality of third carrier signals being transmitted at different frequencies from others of the plurality of third carrier signals from two or more secondary satellites, each fourth carrier signal of the plurality of fourth carrier signals being transmitted at different frequencies from others of the plurality of fourth carrier signals from two or more secondary satellites; each third carrier signal of the plurality of third carrier signals received at different frequencies from two or more secondary satellites and each fourth carrier signal of the plurality of fourth carrier signals received at different frequencies from two or more secondary satellites that results in an inter-channel bias between carrier signals from different ones of the secondary satellites observable at the location-determining receiver;
estimating a first integer ambiguity set associated with the measured first carrier phases, and a second integer ambiguity set associated with the measured second carrier phases;
estimating a third integer ambiguity set associated with the measured third carrier phases and a fourth integer ambiguity set associated with the measured fourth carrier phases;
establishing initial bias data for the inter-channel bias in accordance with a bias initialization procedure that operates in a first mode or a second mode, where in the first mode stored bias data is accessed or retrieved from a look-up table stored in a data storage device associated with the location-determining receiver to populate a real time kinematic engine, where in the second mode stored bias data provides coarse initial data comprising a pre-programmed default bias associated with corresponding hardware of the location-determining receiver;
after the bias initialization procedure, compensating for the inter-channel bias by estimating a compensation factor based on a double difference determination associated with the measured third carrier phase and the fourth carrier phase, where the compensation factor for inter-channel bias in the double difference ambiguity sets is estimated; and
determining, by an estimator of the receiver, a position of the object or the vehicle based on the measured first carrier phases, the measured second carrier phases, the estimated first integer ambiguity set, the estimated second integer ambiguity set, and at least one of the measured third carrier phase and the measured fourth carrier phase, and at least one of the compensated third integer ambiguity set and the compensated fourth integer ambiguity set that are compensated for the inter-channel bias.

2. The method according to claim 1 further comprising:
determining single difference carrier phase measurements or determining single difference pseudo random noise code measurements associated with the secondary satellites to determine associated variances, the measurements assigned a corresponding time stamp or time indicator.

3. The method according to claim 1 wherein the compensating further comprises compensating for the inter-channel bias by estimating the compensation factor based on subtracting the inter-channel bias from a double difference code pre-fit residual associated with the double difference determination.

4. The method according to claim 3 wherein the double difference code pre-fit residual is determined in accordance with the following equation:
λ j Δφ j −λ k Δφ k =∇Δρ k,j +λ j ·ΔN j −λ k ·ΔN k +∇ΔPB k,j +ΔI/f j 2 −ΔI/f k 2 +ε ∇Δφ k,j ,

where Δφ j is a first single-differenced carrier phase observable expressed in units of cycles, Δφ k is a second single-differenced carrier phase observable expressed in units of cycles; λ j and f j are the wavelength and frequency, respectively, of the carrier signal associated with the first single-differenced carrier phase observable; λ k and f k are the wavelength and frequency, respectively, of the carrier signal associated with the second single-differenced carrier phase observable; ΔN j is the first single-differenced integer ambiguity associated with the first single-differenced carrier phase observable; ΔN k is the second single-differenced integer ambiguity associated with the second single-differenced carrier phase observable; ΔI/f j 2 is the single-differenced ionospheric delay for the first single-differenced carrier phase observable, ΔI/f k 2 is the single-differenced ionospheric delay for the second single-differenced carrier phase observable, where I is a function of the Total Electron Content; and ε Δφ kj is the carrier phase observation noise; Δρ k,j is the single-differenced geometry distance; and ΔPB k,j is the inter-channel bias for single-differenced (SD) carrier phase measurements.

5. The method according to claim 1 further comprising:
calibrating the estimation of the inter-channel bias in accordance with a single differenced calibration to allow for changes in the satellites received or available to the location determining receiver by converting the double difference post fit residuals into single difference residuals.

6. The method according to claim 1 further comprising:
assigning time indicators or time stamps for corresponding single difference carrier phase measurements or pseudo random noise code measurements associated with the secondary satellites and for associated variances, and
after processing all epoch data as verified by the time stamps, calibrating the estimation for the inter-channel bias in accordance with a single differenced calibration to allow for changes in the satellites received or available to the location determining receiver by converting the double difference post fit residuals into single difference residuals.

7. The method according to claim 1 further comprising:
monitoring a quality level of the compensation factor, the quality level based on whether there is a significant jump or abrupt change in the magnitude of the compensation factor over a sample time period.

8. The method according to claim 7 further comprising:
monitoring the quality level of the compensation factor, the quality level based on an occurrence of the significant jump and whether a RAIM algorithm flags a single difference code solution or a single difference carrier phase solution as unreliable.

9. The method according to claim 7 further comprising:
resetting bias information for a particular satellite for storing in a look-up table or use by a real time kinematic engine to estimate solutions to ambiguities.

10. The method according to claim 1

Assignees

• Navcorn Tech Inc C/O Deere & Company
• Deere & Co

Inventors

• Dai Liwen
• Wang Chaochao

Classifications

• G01S19/235

  Calibration of receiver components · CPC title

• G01S19/33

  Multimode operation in different systems which transmit time stamped messages, e.g. GPS/GLONASS · CPC title

• G01S19/44 Primary

  Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method · CPC title

• G01S19/425

  by combining or switching between signals derived from different satellite radio beacon positioning systems · CPC title