GNSS sample processor for determining the location of an event

• US 7,551,126 B2
• Filed: 03/08/2007
• Issued: 06/23/2009
• Est. Priority Date: 03/08/2007
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Loomis, Peter Van Wyck, Norda, Carl Jacob
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US11/715,580
• Publication Number:
  US 20080218401A1
• Time in Patent Office: 838 Days
• Field of Search: 342/357.12, 342/357.13
• US Class Current: 342/357.46
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain

Abstract

An apparatus and method for determining a GNSS position of an event where an event capture device writes a short burst of GNSS signal samples with an approximate time into an event data file and a GNSS sample processor reads the event data file some time later for determining the geographical location and an accurate time of the event.

Claims

1. An apparatus for determining a global navigation satellite system (GNSS)-based position from GNSS signal samples recorded in an event data file medium, comprising:

a data file reader for reading an event data file medium, said event data file medium having GNSS signal samples corresponding to GNSS signals received at said event from GNSS satellites and an approximate time tag corresponding to a time said GNSS signals were received, said approximate time tag differing from GNSS clock time by a receiver time error;

a correlation machine for correlating said GNSS signal samples from said event data file medium with local GNSS replicas for measuring code phase offsets corresponding to said GNSS satellites with respect to a local replica clocking offset; and

a GNSS locator including an event time calibrator constructed to use one or more prior or later receiver time errors corresponding to one or more of prior or later events, respectively, for calibrating said approximate time tag; and

a GNSS matrix resolver for using said measured code phase offsets, said calibrated time tag and velocities estimated for said GNSS satellites for a resolution of said local replica clocking offset, said receiver time error and a GNSS-based position of said event.

2. The apparatus of claim 1, wherein:

said GNSS matrix resolver is constructed to use at least said five estimated GNSS satellite velocities for said resolution when said receiver time error places said calibrated time tag within a time uncertainty window greater than a time length of a frame of data bits for said GNSS signals.

3. The apparatus of claim 2, wherein:

said time uncertainty window is greater than thirty seconds.

4. The apparatus of claim 3, wherein:

said time uncertainty window may be up to at least twelve hours.

5. The apparatus of claim 1, wherein:

said GNSS signal samples represent said GNSS signals for a time period less than a time length between transmissions of encoded data bits having a GNSS system clock time.

6. The apparatus of claim 1, further comprising:

a display for displaying textual characters representative of said GNSS-based position together with information for said event in a visible form.

7. The apparatus of claim 1, wherein:

the GNSS locator includes said GNSS matrix resolver for performing said resolution using five said GNSS satellite velocities for compensating for said receiver time error.

8. The apparatus of claim 7, wherein:

said GNSS matrix resolver is constructed for performing said resolution with said GNSS signals for five said GNSS satellites without overdetermination of said GNSS-based position.

9. The apparatus of claim 1, wherein:

the GNSS locator includes said GNSS matrix resolver for using orbital satellite parameters for determining a satellite velocity positioning matrix having K row vectors corresponding to K said satellites, respectively, and five columns, said five columns including three said columns for estimated unit vectors between an estimated said GNSS-based position and estimated locations-in-space of said K GNSS satellites, one said column for a constant, and one said column for estimated range rates between said estimated GNSS-based position and said estimated locations-in-space of said K GNSS satellites, said estimated range rates computed from said estimated unit vectors and said estimated satellite velocities; and

then using said satellite velocity positioning matrix and said measured code phase offsets for said resolution.

10. The apparatus of claim 9, wherein:

said column coefficient for said range rates are calculated as dot products between said estimated unit vectors and said estimated satellite velocities.

11. The apparatus of claim 1, wherein:

the GNSS locator is constructed for using an altitude with said estimated satellite velocities and said measured code phase offsets for four said GNSS satellites for said resolution without overdetermination of said GNSS-based position.

24. The apparatus of claim 1, further comprising:

a satellite velocity calculator to calculate said estimated velocities based on orbital parameters for said GNSS satellites and said calibrated time tag for said GNSS signals.

26. The apparatus of claim 1, wherein:

the GNSS locator is constructed to use one or more prior or later event positions corresponding to prior or later events, respectively, for assisting said resolution of said local replica clocking offset, said receiver time error and said GNSS-based event position.

12. A method for determining a global navigation satellite system (GNSS)-based position from GNSS signal samples recorded in an event data file medium, comprising:

reading an event data file medium an arbitrary time after an event, said event data file medium having GNSS signal samples corresponding to GNSS signals received at said event from GNSS satellites and an approximate time tag corresponding to a time said GNSS signals were received, said approximate time tag differing from GNSS clock time by a receiver time error;

correlating said GNSS signal samples from said event data file medium with local GNSS replicas for measuring code phase offsets corresponding to said GNSS satellites with respect to a local replica clocking offset;

calibrating said approximate time tag based on one or more prior or later receiver time errors corresponding to one or more of prior or later events, respectively; and

using said measured code phase offsets, said calibrated time tag and velocities estimated for said GNSS satellites for resolving said replica clocking offset, said receiver time error and a GNSS-based position of said event.

13. The method of claim 12, wherein:

the step of resolving includes using at least said five estimated GNSS satellite velocities when said receiver time error places said calibrated time tag within a time uncertainty window greater than a time length of a frame of data bits for said GNSS signals.

14. The method of claim 13, wherein:

said time uncertainty window is greater than thirty seconds.

15. The method of claim 14, wherein:

said time uncertainty window may be up to at least twelve hours.

16. The method of claim 12, wherein:

said GNSS signal samples represent said GNSS signals for a time period less than a time length between transmissions of encoded data bits having a GNSS system clock time.

17. The method of claim 12, further comprising:

displaying textual characters representative of said GNSS-based position together with information for said event in a visible form.

18. The method of claim 12, wherein:

resolving includes performing said resolution using five said GNSS satellite velocities for compensating for said receiver time error.

19. The method of claim 12, wherein:

resolving further includes performing said resolution with said GNSS signals for five said GNSS satellites without overdetermination of said GNSS-based position.

20. The method of claim 12, wherein:

resolving includes;

using orbital satellite parameters for determining a satellite velocity positioning matrix having K row vectors corresponding to K said satellites, respectively, and five columns, said five columns including three said columns for estimated unit vectors between an estimated said GNSS-based position and estimated locations-in-space of said K GNSS satellites, one said column for a constant, and one said column for estimated range rates between said estimated GNSS-based position and said estimated locations-in-space of said K GNSS satellites, said estimated range rates computed from said estimated unit vectors and said estimated satellite velocities; and

then using said satellite velocity positioning matrix and said measured code phase offsets for said resolution.

21. The method of claim 20, further comprising:

estimating said estimated range rates as dot products between said estimated unit vectors and said estimated satellite velocities.

22. The method of claim 12, wherein:

resolving includes using an altitude with said estimated satellite velocities and said measured code phase offsets for four said GNSS satellites for said resolution without overdetermination of said GNSS-based position.

25. The method of claim 12, further comprising:

calculating said estimated velocities based on orbital parameters for said GNSS satellites and said calibrated time tag for said GNSS signals.

27. The method of claim 12, wherein:

the step of resolving includes using one or more prior or later event positions corresponding to prior or later events, respectively, for assisting said resolution of said replica clocking offset, said receiver time error and said GNSS-based event position.

23. A tangible medium having computer-readable instructions for reading by a computer for carrying out the following steps:

reading an event data file medium an arbitrary time after an event, said event data file medium having global navigation satellite system (GNSS) signal samples corresponding to GNSS signals received at said event from GNSS satellites and an approximate time tag corresponding to a time said GNSS signals were received, said approximate time tag differing from GNSS clock time by a receiver time error;

correlating said GNSS signal samples from said event data file medium with local GNSS replicas for measuring code phase offsets corresponding to said GNSS satellites with respect to a local replica clocking offset;

calibrating said approximate time tag based on one or more prior or later receiver time errors corresponding to one or more of prior or later events, respectively; and

using said measured code phase offsets, said calibrated time tag and velocities estimated for said GNSS satellites for resolving said local replica clocking offset, GNSS clock times for said GNSS signals and a GNSS-based position of said event.