Continuous Tracking Counter for Enabling Cycle-slip Free Messages in a Network of Global Navigation System Satellite Receivers

• US 20100085253A1
• Filed: 02/20/2009
• Published: 04/08/2010
• 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, Ferguson, Kendall, Allison, Michael Timo
• Granted Patent: US 8,456,359 B2
• Time in Patent Office: Days
• US Class Current: 342/357.410
• 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 satellite tracking information among a network of global navigation satellite system receivers is described. The method includes determining at a first GNSS receiver which satellites in a constellation of satellites have been continuously tracked over a preceding selected time period, and for each such satellite determining its elevation with respect to the zenith. Only the elevation value for the lowest satellite in the set of satellites for which all satellites of higher elevation values have been continuously tracked over the selected time period is then transmitted to the second GNSS receiver. That receiver can then reconstruct the set of satellites which have been continuously tracked.

Claims

1. A method of communicating satellite observable information 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 which satellites in a constellation of satellites have been continuously tracked over a preceding selected time period to thereby define a first set of satellites which have been continuously tracked over the selected time period;

determining an elevation value for each satellite which has been continuously tracked over the preceding selected time period, the elevation values comprising a measure of the closeness of the satellite to a horizontal plane passing through the first location; and

transmitting from the first GNSS apparatus to the second GNSS apparatus a message including only the elevation value of a lowest satellite in the first set of satellites for which all satellites of higher elevation values have been continuously tracked over the selected time period, the lowest satellite and the set of all satellites of higher elevation values that have been continuously tracked over the selected time period forming a second set of satellites.

2. A method as in claim 1 wherein each of the satellites in the constellation of satellites transmits timing information enabling the first GNSS apparatus to determine its location, the method further comprising at the second GNSS apparatus using timing information from only the second set of satellites.

3. A method as in claim 2 wherein the message comprises a first indicator in a first portion of the message, the first indicator specifying whether a second portion of the message includes the continuous tracking information.

4. A method as in claim 3 wherein the second portion of the message includes the elevation value of the lowest satellite in the first set of satellites.

5. A method as in claim 4 wherein if the first indicator does not specify that the second portion of the message includes the continuous tracking information, then no second portion of the message is provided to the second GNSS apparatus.

6. A method as in claim 1 wherein the preceding selected time comprises a first longer time interval, and the method further comprises:

determining at the first GNSS apparatus which satellites in a constellation of satellites have been continuously tracked over a preceding shorter time interval to thereby define a third set of satellites which have been continuously tracked over the shorter time interval;

determining an elevation value for each satellite which has been continuously tracked over the shorter time interval, the elevation values comprising a measure of the closeness of the satellite to the horizontal plane; and

transmitting from the first GNSS apparatus to the second GNSS apparatus a further message including only the elevation value of a lowest satellite in the third set of satellites for which all satellites of higher elevation values have been continuously tracked over the shorter time interval, the lowest satellite and the set of all satellites of higher elevation values that have been continuously tracked over the shorter time interval forming a fourth set of satellites.

7. A method as in claim 6 wherein each of the satellites in the constellation of satellites transmits timing information enabling the first GNSS apparatus to determine its location, the method further comprising at the second GNSS apparatus using timing information from only the fourth set of satellites.

8. A method as in claim 7 wherein the further message comprises a second indicator in a third portion of the message, the second indicator specifying whether a fourth portion of the message includes the continuous tracking information for the fourth set of satellites.

9. A method as in claim 8 wherein the fourth portion of the message includes the elevation value of the lowest satellite in the fourth set of satellites.

10. A method as in claim 9 wherein if the second indicator does not specify that the fourth portion of the message includes the continuous tracking information, then no fourth portion of the message is provided to the second GNSS apparatus.

11. A method as in claim 3 wherein:

if the message does not include the first indicator, a bit is included in the message for each satellite to designate if any data in the message for that satellite includes a cycle-slip; and

if the bit for a satellite includes a cycle-slip, then data for that satellite is not used by the second GNSS apparatus.

12. A method as in claim 1 wherein the message transmitted from the first GNSS apparatus to the second GNSS apparatus including only the elevation value of a lowest satellite specifies the elevation value.

13. A method as in claim 12 wherein which if the elevation value is 90 degrees, the second set of satellites comprises zero satellites.

14. A method as in claim 6 wherein the shorter time interval has a duration and the fourth portion of the message further indicates the duration of the shorter time interval.