Post-processing of NMEA data

• US 6,490,524 B1
• Filed: 03/07/2000
• Issued: 12/03/2002
• Est. Priority Date: 03/07/2000
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: White, Eric S., Wetherbee, Lisa
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US09/517,117
• Time in Patent Office: 1,001 Days
• Field of Search: 701/213, 701/214, 701/215, 701/207, 342/357.06, 342/357.12, 342/357.1, 342/357.03, 342/357.02, 342/357.17, 342/352
• US Class Current: 701/215
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile

Abstract

A method and system thereof for processing data in real time or post-processing, such as Global Positioning System (GPS) data that have been formatted in the National Marine Electronics Association (NMEA) format. In the GPS embodiment, uncorrected GPS data indicating an estimated position are computed by a receiver via signals from a first broadcaster (e.g., GPS satellites). Differential GPS (DGPS) data are received by the receiver via a signal from a second broadcaster (e.g., a GPS base station). A message is generated by the receiver when the signal from the second broadcaster is not received. The message contains information sufficient to identify the DGPS data stored by the second broadcaster needed to correct the uncorrected GPS data. The message and the uncorrected GPS data are stored by the receiver for subsequent processing. The DGPS data are retrieved from the second broadcaster, and the message is used to identify the DGPS data required to correct the uncorrected information. The uncorrected GPS data are correlated with the DGPS data and corrected.

Claims

1. A method for processing Global Positioning System (GPS) data, said method comprising the steps of:

a) receiving uncorrected GPS data indicating an estimated position; and

b) generating a message comprising information sufficient to identify differential GPS (DGPS) data needed to correct said uncorrected GPS data, wherein said message is generated in lieu of receiving said DGPS data and wherein said message comprises a time tag corresponding to said estimated position, an identifier tag identifying a first broadcaster that is a source of said GPS data, and IODE (issue of data ephemeris) information.

2. The method for processing GPS data as recited in claim 1 further comprising the step of:

c) using said message to select DGPS data needed to correct said uncorrected GPS data.

3. The method for processing GPS data as recited in claim 2 further comprising the step of:

d) generating corrected GPS data using said DGPS data needed to correct said uncorrected GPS data, wherein said corrected GPS data indicate a corrected position.

4. The method for processing GPS data as recited in claim 3 wherein said step d) further comprises:

correlating said information in said message with said uncorrected GPS data using a time tag in said message and a time tag in said uncorrected GPS data.

5. The method for processing GPS data as recited in claim 3 wherein said steps b) through d) are performed in real time substantially as said uncorrected GPS data and said DGPS data are received.

6. The method for processing GPS data as recited in claim 3 wherein said uncorrected GPS data and said corrected GPS data are substantially compliant with a National Marine Electronics Association (NMEA) format.

7. The method for processing GPS data as recited in claim 6 wherein said uncorrected GPS data and said corrected GPS data are substantially equivalent to data contained in a NMEA sentence selected from a group consisting of:

a GGA sentence, a GSA sentence, a GNS sentence, a GLL sentence, a PTNL,GGK sentence, and a RMC sentence.

8. The method for processing GPS data as recited in claim 7 further comprising the step of:

replacing in a NMEA sentence said estimated position with said corrected position.

9. The method for processing GPS data as recited in claim 1 wherein said DGPS data are received from a second broadcaster.

10. The method for processing GPS data as recited in claim 9 wherein said first broadcaster is a GPS satellite and said second broadcaster is a GPS base station.

11. The method for processing GPS data as recited in claim 1 further comprising the step of:

correlating agricultural data to said corrected position.

12. A method for processing Global Positioning System (GPS) data, said method comprising the steps of:

a) receiving uncorrected GPS data in a signal from a first broadcaster, said uncorrected GPS data indicating an estimated position;

b) receiving differential GPS (DGPS) data in a signal from a second broadcaster, said DGPS data used for correcting said estimated position when said signal from said second broadcaster is available, said correcting using said DGPS data performed substantially as said uncorrected GPS data and said DGPS data are received;

c) generating a message when said signal from said second broadcaster is not received, said message containing information sufficient to identify DGPS data needed to correct said uncorrected GPS data;

d) using said message to select DGPS data needed to correct said uncorrected GPS data;

e) generating corrected GPS data using said DGPS data needed to correct said uncorrected GPS data, wherein said corrected GPS data indicate a corrected position; and

f) replacing in a National Marine Electronics Association (NMEA) sentence said estimated position with said corrected position.

13. The method for processing GPS data as recited in claim 12 wherein said steps c) through e) are performed in real time substantially as said uncorrected GPS data and said DGPS data needed to correct said uncorrected GPS data are received.

14. The method for processing GPS data as recited in claim 12 wherein said uncorrected GPS data and said corrected GPS data are substantially compliant with a NMEA format.

15. The method for processing GPS data as recited in claim 14 wherein said uncorrected GPS data and said corrected GPS data are substantially equivalent to data contained in a NMEA sentence selected from a group consisting of:

a GGA sentence, a GSA sentence, a GNS sentence, a GLL sentence, a PTNL,GGK sentence, and a RMC sentence.

16. The method for processing GPS data as recited in claim 12 wherein said first broadcaster is a GPS satellite and said second broadcaster is a GPS base station.

17. The method for processing GPS data as recited in claim 12 wherein said information in said message comprises a time tag corresponding to said estimated position when said signal from said second broadcaster is not received, an identifier tag that identifies said first broadcaster, and IODE (issue of data ephemeris) information.

18. The method for processing GPS data as recited in claim 12 wherein said step e) further comprises:

correlating said information in said message with said uncorrected GPS data using a time tag in said message and a time tag in said uncorrected GPS data.

19. The method for processing GPS data as recited in claim 12 further comprising the step of:

correlating agricultural data to said corrected position.

20. A computer system comprising:

an address/data bus;

a computer-readable memory unit coupled to said address/data bus;

a processor coupled to said address/data bus, said processor for performing a method of processing Global Positioning System (GPS) data, said method comprising the steps of;

a) receiving uncorrected GPS data indicating an estimated position; and

b) generating a message comprising information sufficient to identify differential GPS (DGPS) data needed to correct said uncorrected GPS data, wherein said message is generated in lieu of receiving said DGPS data and wherein said message comprises a time tag corresponding to said estimated position, an identifier tag identifying a first broadcaster that is a source of said GPS data, and IODE (issue of data ephemeris) information.

21. The computer system of claim 20 wherein said method further comprises the step of:

c) using said message to select DGPS data needed to correct said uncorrected GPS data.

22. The computer system of claim 21 wherein said method further comprises the step of:

d) generating corrected GPS data using DGPS data needed to correct said uncorrected GPS data, wherein said corrected GPS data indicate a corrected position.

23. The computer system of claim 22 wherein said steps b) through d) of said method are performed in real time substantially as said uncorrected GPS data and said DGPS data are received.

24. The computer system of claim 22 wherein said uncorrected GPS data and said corrected GPS data are substantially compliant with a National Marine Electronics Association (NMEA) format.

25. The computer system of claim 24 wherein said uncorrected GPS data and said corrected GPS data are substantially equivalent to data contained in a NMEA sentence selected from a group consisting of:

a GGA sentence, a GSA sentence, a GNS sentence, a GLL sentence, a PTNL,GGK sentence, and a RMC sentence.

26. The computer system of claim 25 wherein said method further comprises the step of:

replacing in a NMEA sentence said estimated position with said corrected position.

27. The computer system of claim 20 wherein said method further comprises the step of:

correlating said information in said message with said uncorrected GPS data using a time tag in said message and a time tag in said uncorrected GPS data.

28. The computer system of claim 20 wherein said method further comprises the step of:

correlating agricultural data to said corrected position.

29. The computer system of claim 20 further comprising:

a receiver for receiving said uncorrected GPS data in a signal from said first broadcaster and said DGPS data in a signal from a second broadcaster.

30. The computer system of claim 29 wherein said first broadcaster is a GPS satellite and said second broadcaster is a GPS base station.

31. The computer system of claim 20 wherein said uncorrected GPS data and said message are stored in said computer-readable memory unit.

32. The computer system of claim 20 wherein said uncorrected GPS data and said message are stored in an external memory device.