Enhanced differential GNSS carrier-smoothed code processing using dual frequency measurements

• US 6,198,430 B1
• Filed: 03/26/1999
• Issued: 03/06/2001
• Est. Priority Date: 03/26/1999
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Hwang, Patrick A., Bader, John R., McGraw, Gary A.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/277,341
• Time in Patent Office: 711 Days
• Field of Search: 342/357.03, 701/215
• US Class Current: 342/357.27
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile

Abstract

A method of generating a differentially corrected pseudorange residual in a differential global positioning system includes tracking at a base station first and second GPS signals, having first and second frequencies, from a first satellite. At the base station, a first pseudorange measurement is determined from the tracked first GPS signal. At the base station, a first smoothed pseudorange measurement is calculated from the determined first pseudorange measurement as a function of both the first and second GPS signals. The first smoothed pseudorange measurement is provided to a remote GPS receiver. The remote GPS receiver calculates the differentially corrected pseudorange residual as a function of the first smoothed pseudorange measurement provided by the base station.

Claims

1. A method of generating a differentially-corrected divergence-free carrier-smoothed pseudorange residual in a differential global positioning system, the method comprising:

tracking at a dual frequency base station a first GPS signal, having a first frequency, from a first satellite;

tracking at the base station a second GPS signal, having a second frequency, from the first satellite;

determining at the base station a first pseudorange measurement ρ

₁^B from the tracked first GPS signal;

determining at the base station a first carrier phase measurement φ

₁^B from the tracked first GPS signal;

determining at the base station a second carrier phase measurement φ

₂^B from the tracked second GPS signal;

calculating at the base station a phase difference Δ

φ

^B between the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B;

calculating at the base station a first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B from the first pseudorange measurement ρ

₁^B, the first carrier phase measurement φ

₁^B, and the phase difference Δ

φ

^B;

deriving at the base station a differential correction from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B;

providing the differential correction derived from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B to a remote GPS receiver;

providing the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B or the phase difference Δ

φ

^B to the remote GPS receiver; and

calculating at the remote GPS receiver the differentially-corrected divergence-free carrier smoothed-pseudorange residual.

2. The method of claim 1 wherein the step of calculating at the base station the first divergence-free carrier smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B further comprises;

subtracting the phase difference Δ

φ

^B from the first carrier phase measurement φ

₁^B to obtain a generalized carrier phase measurement Φ

;

subtracting the generalized carrier phase measurement Φ

from the first pseudorange measurement ρ

₁^B to obtain a differenced data signal χ

;

filtering the differenced data signal χ

to obtain a filtered output data signal {circumflex over (χ

)}; and

adding the generalized carrier phase measurement Φ

to the filtered output data signal {circumflex over (χ

)} to obtain the first divergence-free carrier smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

3. The method of claim 1 and further comprising:

determining at the dual frequency base station a second pseudorange measurement ρ

₂^B from the tracked second GPS signal;

calculating at the base station a second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B from the second pseudorange measurement ρ

₂^B, the second carrier phase measurement φ

₂^B, and the phase difference Δ

φ

^B;

deriving a differential correction from the second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B;

providing the differential correction derived from the second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B to a remote GPS receiver; and

calculating at the remote GPS receiver the differentially-corrected divergence-free carrier-smoothed pseudorange residual.

4. The method of claim 1 wherein the remote GPS receiver is a conventional GPS receiver, the method at the conventional remote GPS receiver further comprising:

tracking the first GPS signal;

determining a first pseudorange measurement ρ

₁^A from the tracked first GPS signal;

determining a first carrier phase measurement φ

₁^A from the tracked first GPS signal;

calculating a first smoothed pseudorange measurement {circumflex over (Ψ

)}_1C^A from the first pseudorange measurement ρ

₁^A and the first carrier phase measurement φ

₁^A; and

calculating a differentially-corrected pseudorange residual Δ

Ψ

_1C as a function of a difference between the first smoothed pseudorange measurement {circumflex over (Ψ

)}_1C^A and the differential correction derived from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

5. The method of claim 1 wherein the remote GPS receiver is an enhanced single frequency GPS receiver, the method at the enhanced remote GPS receiver further comprising:

tracking the first GPS signal;

determining a first pseudorange measurement ρ

₁^A from the tracked first GPS signal;

determining a first carrier phase measurement φ

₁^A from the tracked first GPS signal;

calculating a first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_1B^A from the first pseudorange measurement ρ

₁^A, the first carrier phase measurement φ

₁^A, and the phase difference Δ

φ

^B; and

calculating a differentially-corrected pseudorange residual Δ

Ψ

_1B as a function of a difference between the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_1B^A and the differential correction derived from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

6. The method of claim 1 wherein the enhanced single frequency remote GPS receiver calculates the phase difference Δ

φ

^B between the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B.

7. The method of claim 1 wherein the remote GPS receiver is an enhanced dual frequency GPS receiver, the method at the enhanced remote GPS receiver further comprising:

tracking the first GPS signal;

tracking the second GPS signal;

determining a first pseudorange measurement ρ

₁^A from the tracked first GPS signal;

determining a first carrier phase measurement φ

₁^A from the tracked first GPS signal;

determining a second carrier phase measurement φ

₂^A from the tracked second GPS signal;

calculating a first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^A from the first pseudorange measurement ρ

₁^A, the first carrier phase measurement φ

₁^A, and the second carrier phase measurement φ

₂^A; and

calculating a differentially-corrected pseudorange residual Δ

Ψ

_1D as a function of a difference between the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^A and the differential correction derived from first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

8. The method of claim 3 wherein the remote GPS receiver is an enhanced dual frequency GPS receiver, the method at the enhanced remote GPS receiver further comprising:

tracking the second GPS signal;

determining a second pseudorange measurement ρ

₂^A from the tracked second GPS signal;

determining a second carrier phase measurement φ

₂^A from the tracked second GPS signal;

calculating a second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_2B^A from the second pseudorange measurement ρ

₂^A, the second carrier phase measurement φ

₂^A, and the phase difference Δ

φ

^B; and

calculating a differentially-corrected pseudorange residual Δ

Ψ

_2B as a function of a difference between the second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_2B^A and the differential correction derived from second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B.

9. The method of claim 8 wherein the enhanced GPS receiver calculates the phase difference Δ

φ

^B between the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B.

10. A differential global positioning system for generating a differentially-corrected divergence-free carrier-smoothed pseudorange residual comprising:

a dual frequency base station for tracking from a GPS satellite a first signal at a first frequency and a second signal at a second frequency, said dual frequency base station further comprising;

a carrier phase differencing node for calculating a phase difference Δ

φ

^B between a first carrier phase measurement φ

₁^B of the first signal and a second carrier phase measurement φ

₂^B of the second signal;

a divergence-free carrier smoothing filter for calculating a divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B from a first pseudorange measurement ρ

₁^B of the first signal, the first carrier phase measurement φ

₁^B, and the phase difference Δ

φ

^B;

a differential correction generator for calculating a differential correction derived from the divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B; and

a communications device for transmitting the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B or the phase difference Δ

φ

^B and the differential correction derived from the divergence-free carrier-smoothed pseudorange measurement; and

a remote GPS receiver for receiving over the communications device the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B or the phase difference Δ

φ

^B and the differential correction derived from the divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B and for calculating the differentially-corrected divergence-free carrier-smoothed pseudorange residual.

11. The differential global positioning system of claim 10 wherein the dual frequency base station further comprises a second divergence-free carrier smoothing filter for calculating a second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B from a second pseudorange measurement ρ

₂^B from the second signal, the second carrier phase measurement φ

₂^B, and the phase difference Δ

φ

^B.

12. The differential global positioning system of claim 11 wherein the dual frequency base station further comprises a second differential correction generator for calculating a second differential correction derived from the second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B.

13. The differential global positioning system of claim 12 wherein the communications device further provides the second differential correction derived from the second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B to the remote GPS receiver.

14. The differential global positioning system of claim 10 wherein the remote GPS receiver is a conventional GPS receiver for tracking the first signal, said conventional GPS receiver further comprising:

a conventional carrier smoothing filter for calculating a first remote carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_1C^A from a first remote pseudorange measurement ρ

₁^A and a first remote carrier phase measurement φ

₁^A from the first signal; and

a differential processor for calculating a differentially-corrected pseudorange residual Δ

Ψ

_1C as a function of the first remote carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_1C^A and the differential correction derived from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

15. The differential global positioning system of claim 10 wherein the remote GPS receiver is an enhanced single frequency GPS receiver for tracking the first signal, said enhanced GPS receiver further comprising:

a divergence-free carrier smoothing filter for calculating a first remote divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_1B^A from a first remote pseudorange measurement ρ

₁^A and a first remote carrier phase measurement φ

₁^A of the first signal, and the phase difference Δ

φ

^B; and

a differential processor for calculating a differentially-corrected pseudorange residual Δ

Ψ

_1B as a function of the first remote divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_1B^A and the differential correction derived from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

16. The differential global positioning system of claim 15 wherein the enhanced GPS receiver further comprises a carrier phase differencing node for calculating the phase difference Δ

φ

^B between the first carrier phase measurement φ

₁^B of the first signal and the second carrier phase measurement φ

₂^B of the second signal received from the uplink.

17. The differential global positioning system of claim 10 wherein the remote GPS receiver is an enhanced dual frequency GPS receiver for tracking the first signal and the second signal, said enhanced GPS receiver further comprising:

a divergence-free carrier smoothing filter for calculating a second remote divergence-free carrier-smoothed pseudorange measurement Ψ

₁^A from a first remote pseudorange measurement ρ

₁^A and a first remote carrier phase measurement φ

₁^A from the first signal and a second remote carrier phase measurement φ

₂^A from the second signal; and

a differential processor for calculating a differentially-corrected pseudorange residual Δ

Ψ

_1D as a function of the second remote divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^A and differential correction derived from the first divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₁^B.

18. The differential global positioning system of claim 13 wherein the remote GPS receiver is an enhanced dual frequency GPS receiver for tracking the second GPS signal, said enhanced GPS receiver further comprising:

a divergence-free carrier smoothing filter for calculating a third divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_2B^A from a second remote pseudorange measurement ρ

₂^A and a second remote carrier phase measurement φ

₂^A from the second signal and the phase difference Δ

φ

^B between the first carrier phase measurement φ

₁^B and the second carrier phase measurement φ

₂^B; and

a differential processor for calculating a differentially-corrected pseudorange residual Δ

Ψ

_2B as a function of the third remote divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}_2B^A and differential correction derived from the second divergence-free carrier-smoothed pseudorange measurement {circumflex over (Ψ

)}₂^B.

19. The differential global positioning system of claim 18 wherein the remote enhanced GPS receiver further comprises a carrier phase differencing node for calculating the phase difference Δ

φ

^B between the first carrier phase measurement φ

₁^B of the first signal and a second carrier phase measurement φ

₂^B of the second signal received from the uplink.