Systems and methods for detecting GPS measurement errors

• US 7,821,454 B2
• Filed: 11/20/2007
• Issued: 10/26/2010
• Est. Priority Date: 11/20/2007
• Status: Expired due to Fees

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Liao, Daniel, Chansarkar, Mangesh, Xie, Gang, Lin, Xiangdong
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): GALT, CASSI J
• Application Number:
  US11/942,912
• Publication Number:
  US 20090128407A1
• Time in Patent Office: 1,071 Days
• Field of Search: 342/357.06, 342/357.08, 342/357.12, 342/357.15, 342/357.02
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

Systems and methods for detecting global positioning system (GPS) measurement errors are provided. In this regard, a representative system, among others, includes a navigation device that is configured to receive GPS signals from signal sources, the navigation device being configured to calculate pseudoranges (PRs) and delta ranges (DRs) based on the received GPS signals, the navigation device including a consistency check algorithm that is configured to: determine mismatches between the respective calculated PRs and DRs, and indicate that an error exists in the respective calculated PRs and DRs based on their mismatch and mismatch accumulations. This algorithm can be independent of navigation state and is capable of detecting slow-changing errors.

Claims

1. A system for detecting global positioning system (GPS) measurement errors comprising:

a navigation device configured to receive GPS signals from signal sources, the navigation device being configured to calculate pseudoranges (PRs) and delta ranges (DRs) based on the received GPS signals, the navigation device including a consistency check algorithm configured to;

calculate delta PRs;

determine whether at least one difference between respective calculated delta PRs and DRs exceeds a first threshold; and

in response to determining that the at least one difference does not exceed the first threshold, accumulate the differences between the respective calculated delta PRs and DRs, determine whether the accumulation of the differences between the respective calculated delta PRs and DRs exceeds a second threshold, and indicate that an error exists in the respective calculated PRs and DRs if the accumulation of the differences exceeds the second threshold.

2. The system as defined in claim 1, wherein the consistency check algorithm is further configured to send an error message to a navigation algorithm responsive to determining that the at least one of the mismatches exceeds the first threshold.

3. The system as defined in claim 1, wherein the consistency check algorithm is further configured to send the calculated PR and DR to a navigation algorithm responsive to determining that the at least one of the mismatches does not exceed the first threshold.

11. The system as defined in claim 1, wherein the first threshold is determined based on statistics relating to test measurement data for normal GPS receiver operation.

12. The system as defined in claim 11, wherein the first threshold is a function of carrier-to-noise ratio (CN0).

13. The system as defined in claim 1, wherein accumulating the differences between the respective calculated delta PRs and DRs is performed based on:

|(pr_k−

pr<sub>k−

n−

1</sub>)−

(dr_k+ . . . +dr<sub>k−

n</sub>)|<

threshold_n+1,

where n+1 represents a number of seconds during which measurements are accumulated.

4. A method for measuring global positioning system (GPS) errors comprising:

receiving GPS signals from signal sources;

calculating pseudoranges (PR) and delta ranges (DR) based on the received GPS signals;

calculating delta PRs;

determining whether mismatches exist between respective calculated delta PRs and DRs based on a first threshold; and

in response to determining that one or more mismatches exist, accumulating delta PR and DR mismatches and performing a consistency check involving the accumulated delta PR and DR mismatches based on a second threshold.

5. The method as defined in claim 4, further comprising:

determining whether at least one of the mismatches between the respective calculated delta PRs and DRs exceeds the first threshold; and

responsive to determining that the at least one of the differences exceeds the first threshold, indicating that an error exists in the respective calculated delta PRs and DRs.

6. The method as defined in claim 4, further comprising sending an error message to a navigation algorithm responsive to determining that the at least one of the mismatches exceeds the first threshold.

7. The method as defined in claim 4, further comprising sending the calculated PR and DR to a navigation algorithm responsive to determining that the at least one of the mismatches does not exceed the first threshold.

8. A global positioning system (GPS) receiver comprising:

an antenna that receives GPS signals from signal sources;

a digital signal processing (DSP) configured to receive the GPS signals from the antenna, the DSP being configured to calculate pseudoranges (PRs) and delta ranges (DRs) based on the received GPS signals; and

a consistency check algorithm configured to;

determine whether one or more mismatches exist between respective calculated delta PRs and DRs, and

in response to determining that one or more mismatches exist, accumulate delta PR and DR mismatches and perform a consistency check involving the accumulated delta PR and DR mismatches based on a threshold.

9. The GPS receiver as defined in claim 8, wherein the consistency check algorithm is further configured to send the calculated PR and DR to a navigation algorithm responsive to determining that the at least one of the mismatches does not exceed a mismatch threshold.

10. A global positioning system (GPS) receiver comprising:

an antenna that receives GPS signals from signal sources;

a digital signal processing (DSP) that receives the GPS signals from the antenna, the DSP being configured to calculate pseudoranges (PRs) and delta ranges (DRs) based on the received GPS signals; and

a consistency check algorithm that is configured to;

calculate delta PRs;

accumulate differences between respective calculated delta PRs and DRs based on whether one or more mismatches exist between the respective calculated delta PRs and DRs,

determine whether the accumulation of the differences between respective calculated delta PRs and DRs exceeds a threshold; and

responsive to determining that the accumulation of the differences exceeds the threshold, indicate that an error exists in the respective calculated PRs and DRs.