Continuous tracking counter for enabling cycle-slip free messages in a network of global navigation system satellite receivers

• US 8,456,359 B2
• Filed: 02/20/2009
• Issued: 06/04/2013
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Ferguson, Kendall, Allison, Michael Timo, Albright, Michael
• Primary Examiner(s): Keith, Jack W
• Assistant Examiner(s): MCGUE, FRANK J
• Application Number:
  US12/389,677
• Publication Number:
  US 20100085253A1
• Time in Patent Office: 1,565 Days
• Field of Search: 342/357.67, 342/357.09, 335/767, 335/709
• US Class Current: 342/357.67
• 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 global navigation satellite system (GNSS) apparatus comprising:

determining at the GNSS apparatus which satellites in a constellation of satellites have been continuously tracked over at least two time periods to identify satellites which have been continuously tracked over a first time period of the at least two time periods, and to identify satellites which have been continuously tracked over a second time period of the at least two time periods;

determining an elevation value for each satellite which has been continuously tracked over the first time period;

transmitting from the GNSS apparatus a message which does not include the elevation values of all of the satellites which have been continuously tracked over the at least two time periods, but the message does include one elevation value of the satellites which have been continuously tracked over the first time period, and wherein;

the one elevation value is the elevation value of the lowest satellite which has been continuously tracked over the first time period; and

the message comprises a first indicator in a first portion of the message specifying whether at least a second portion of the message includes master and minor continuous tracking information.

2. A method as in claim 1 wherein the second portion of the message includes the elevation value of the lowest satellite which has been continuously tracked over the first time period.

3. A method as in claim 2 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 transmitted.

4. A method as in claim 2 wherein the second portion of the message includes both master continuous tracking information and minor continuous tracking information.

5. A method as in claim 4 wherein the master continuous tracking information includes the elevation value in a block of data accompanying the message, and the minor continuous tracking information includes numeric values for each satellite tracked.

6. A method as in claim 1 wherein the first time period is longer than the second time period, and the method further comprises:

determining at the GNSS apparatus which satellites in a constellation of satellites have been continuously tracked over the second time period;

setting numeric values for each satellite which has been continuously tracked over the second time period, the numeric values indicating the periods of continuous tracking; and

transmitting from the GNSS apparatus a message which includes the numeric values.

7. A method as in claim 6 further comprising:

at another GNSS apparatus receiving the message from the GNSS apparatus; and

at the another GNSS apparatus using the satellite observable information from satellites having an elevation value at least as high as the elevation value of the lowest satellite.

8. A method as in claim 1 wherein:

if the message does not include the first indicator, a bit is included in the message for each satellite to designate if any observables data in the message for that satellite has suffered a loss of continuous signal tracking; and

if the bit for included in the message designates a loss of continuous tracking, then the observables data for that satellite is indicated as having suffered a loss of continuous tracking is not used for applications requiring continuous tracking.

9. A method as in claim 8 wherein if the elevation value is 90 degrees, the elevation value indicates that there are no satellites which have been continuously tracked over the first time period.

10. A method as in claim 6 wherein the second time period has either (i) a single duration or (ii) a range of durations, and the minor continuous tracking information in the message provides a value which indicates either (i) or (ii).