Method of compactly communicating ionospheric and tropospheric corrections in a network of global navigation system satellite receivers

• US 8,044,849 B2
• Filed: 02/20/2009
• Issued: 10/25/2011
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Albright, Michael, Remondi, Benjamin W., Ferguson, Kendall, Allison, Michael Timo
• Primary Examiner(s): Phan; Dao
• Application Number:
  US12/389,689
• Publication Number:
  US 20100085248A1
• Time in Patent Office: 977 Days
• Field of Search: 342/357.24, 342/357.26, 342/357.34, 342/357.44, 342/357.41, 701/213, 701/215
• US Class Current: 342/357.44
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/073 involving a network of fixed stations
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction

Abstract

A method of communicating corrections for information related to satellite signals among global navigation satellite system (GNSS) receivers is described. An ionosphere correction for ionosphere signal path delay is determined for a first satellite. This ionosphere correction is then compared to an ionosphere correction for ionosphere signal path delay for a satellite assumed to be directly over the receiver. The receiver then sends a message which includes only the difference between the ionosphere correction for the actual observation and the ionosphere correction for a satellite assumed to be at the zenith.

Claims

1. A method of communicating corrections for information related to satellite signals from a first global navigation satellite system (GNSS) apparatus at a first location to a second GNSS apparatus at a second location comprising:

determining at the first GNSS apparatus for a first satellite in a constellation of satellites a first ionosphere correction for ionosphere signal path delay;

determining at the first GNSS apparatus a second ionosphere correction for a second satellite which is assumed to be directly over the first location;

comparing the first ionosphere correction to the second ionosphere correction for ionosphere signal path delay;

calculating a difference between the first ionosphere correction and the second ionosphere correction; and

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only the difference between the first ionosphere correction and the second ionosphere correction.

2. A method as in claim 1 further comprising:

determining for each of a plurality of additional satellites in the constellation of satellites a corresponding ionosphere correction for ionosphere signal path delay;

comparing each of the corresponding ionosphere corrections to the second correction;

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only differences between the corresponding ionosphere correction for ionosphere signal path delay and the second correction.

3. A method as in claim 2 wherein:

the first ionosphere correction comprises a determination of first path length through the ionosphere for the first satellite signal; and

the second ionosphere correction comprises a determination of a second path length through the ionosphere for the satellite assumed to be directly over the first location.

4. A method as in claim 3 wherein the difference between the first ionosphere correction and the second ionosphere correction comprises the difference between the first path length and the second path length.

5. A method as in claim 3 wherein:

for each of the plurality of additional satellites in the constellation of satellites the corresponding ionosphere correction for ionosphere signal path delay includes a determination of a path length through the ionosphere for each such satellite to the first location;

for each of the plurality of additional satellites comparing the path length through the ionosphere to the second path length; and

for each of the plurality additional satellites, transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only results of the step of comparing the path length through the ionosphere to the second path length.

6. A method as in claim 1 further comprising:

determining at the first GNSS apparatus for a first satellite in a constellation of satellites a first troposphere correction for troposphere signal path delay;

comparing the first troposphere correction to a second troposphere correction for troposphere signal path delay, the second troposphere correction being a troposphere correction for troposphere signal path delay in a fixed amount; and

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only a difference between the first troposphere correction and the fixed amount.

7. A method as in claim 6 further comprising:

determining for each of a plurality of additional satellites in the constellation of satellites a corresponding troposphere correction for troposphere signal path delay;

comparing each of the corresponding troposphere corrections to the second correction;

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only differences between the corresponding troposphere correction for troposphere signal path delay and the second correction.

8. A method as in claim 7 wherein:

the first troposphere correction comprises a determination of first path length through the troposphere for the first satellite signal; and

the second troposphere correction comprises a fixed value.

9. A method as in claim 8 wherein:

for each of the plurality of additional satellites in the constellation of satellites the corresponding troposphere correction for troposphere signal path delay includes a determination of a path length through the troposphere for each such satellite to the first location;

for each of the plurality of additional satellites comparing the path length through the ionosphere to the fixed value; and

for each of the plurality of additional satellites, transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only results of the step of comparing the path length through the troposphere to the fixed value.

10. A method as in claim 8 wherein the fixed value is determined using an approximation of the Hopfield model for troposphere signal delay.

11. A method as in claim 10 further comprising:

determining at the first GNSS apparatus for a first satellite in a constellation of satellites a first ionosphere correction for ionosphere signal path delay;

comparing the first ionosphere correction to a second ionosphere correction for ionosphere signal path delay, the second correction being for ionosphere signal path delay being for a satellite assumed to be directly over the first location; and

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only a difference between the first ionosphere correction and the second ionosphere correction.

12. A method as in claim 11 further comprising:

determining for each of a plurality of additional satellites in the constellation of satellites a corresponding ionosphere correction for ionosphere signal path delay;

comparing each of the corresponding ionosphere corrections to the second correction;

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only differences between the corresponding ionosphere correction for ionosphere signal path delay and the second correction.

13. A method as in claim 12 wherein:

the first ionosphere correction comprises a determination of first path length through the ionosphere for the first satellite signal; and

the second ionosphere correction comprises a determination of a second path length through the ionosphere for the satellite assumed to be directly over the first location.

14. A method as in claim 13 wherein the difference between the first ionosphere correction and the second ionosphere correction comprises the difference between the first path length and the second path length.

15. A method as in claim 14 wherein:

for each of the plurality of additional satellites in the constellation of satellites the corresponding ionosphere correction for ionosphere signal path delay includes a determination of a path length through the ionosphere for each such satellite to the first location;

for each of the plurality of additional satellites comparing the path length through the ionosphere to the second path length; and

for each of the plurality additional satellites, transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only results of the step of comparing the path length through the ionosphere to the second path length.