Compact Transmission of GPS Information Using Compressed Measurement Record Format

• US 20100085249A1
• 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, Remondi, Benjamin W., Ferguson, Kendall, Allison, Michael Timo
• Granted Patent: US 8,031,111 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 format for providing messages among GNSS apparatus includes providing a message identification block and a message body. The message identification block includes information specifying a message length and a message type block specifying a message type. Rather than sending all data from one apparatus to another, ambiguous observation data is sent to conserve bandwidth. At the sender a deconstruction of GNSS code and carrier observations using knowledge of the signal structure and constellation geometry, together with simplifications of atmospheric models, allows removal from the observation data of that information which can be implicitly understood or recreated by the recipient. This enables only the necessary information to be packed for transmission to the recipient.

Claims

1. A message format for transmission of data between a first global navigation satellite system (GNSS) apparatus at a first location to a second GNSS apparatus at a second location comprising:

a message identification block having a message length block specifying a message length and a message type block specifying a message type; and

a message body.

2. A message format as in claim 1 wherein the message length block specifies one of three message lengths of which zero bits is one message length.

3. A message format as in claim 1 wherein the message body comprises GNSS observation data from the first GNSS apparatus.

4. A message format as in claim 3 wherein the GNSS observation data comprises:

a GNSS observation header block specifying at least a sequence number which increments with each GNSS epoch; and

an epoch base time length bit which specifies a size in bits of the epoch base time.

5. A message format as in claim 4 wherein the GNSS observation header block further comprises at least one of:

an epoch continuation flag designating whether there are additional messages having the same epoch base time;

a cyclic redundancy check flag designating if there is cyclic redundancy check data present in the message; and

a kinematic flag to designate if the first GNSS apparatus is at a fixed location or is moving.

6. A message format as in claim 4 further comprising at least one of:

a station health block present bit designating whether a station health block is present in the message;

a position block present bit indicating if a position block is present in the message; and

a site information block bit indicating if a site information block is present in the message.

7. A message format as in claim 6 wherein:

if the station health block present bit is active, then a station health block is present in the message which specifies if the GNSS apparatus at the first location is usable, is monitored but unhealthy, or is monitored and healthy;

if the position block present bit is active, the a position block is present and indicates

at least a part of latitude and longitude of the first location; and

if the site information present bit is active then a site information block is present and indicates at least a site name and site code.

8. A message format as in claim 7 further comprising a pseudo-random noise capacity specification block to define a number of bits present in a pseudo-random noise block.

9. A message format as in claim 8 further comprising a GNSS observation block present bit indicating if a GNSS observation block is present in the message.

10. A message format as in claim 9 wherein if the GNSS observation block present bit is active, a GNSS observation block is present in the message which GNSS observation block provides positional information for the first location.

11. A message format as in claim 10 wherein the GNSS observation block comprises a definition block which specifies a number of epochs over which the positional information for the first location will be transferred and the positional information for the first location.

12. A message format as in claim 11 wherein the number of epochs extends from one to 2n where n is an integer.

13. A message format as in claim 4 wherein the GNSS observation header block comprises at least one of:

an epoch fractional seconds block designating whether sub-one second epoch intervals are present; and

a reference station alias block providing an alias for the first GNSS apparatus to identify data from multiple GNSS apparatus delivered over a single logical channel.

14. A message format as in claim 10 wherein the GNSS observation block includes:

an Age of Position block indicating whether the first location has changed since a previous message; and

the positional information for the first location includes latitude, longitude and height.

15. A message as in claim 7 wherein the site information block further comprises:

site information definition bits to specify a number of epochs over which the site information will be transmitted; and

information about at least one of an antenna coupled to the first GNSS apparatus and the GNSS apparatus itself.

16. A message format as in claim 1 wherein the message body comprises:

a GNSS observation data header block including a GNSS observation data present bit which when active indicates that GNSS observations from the first GNSS apparatus are included in the message body; and

if the GNSS observation data present bit is active, a GNSS observation block that includes the GNSS observations from the first GNSS receiver.

17. A message format as in claim 16 wherein the GNSS observation block further comprises:

a definition block specifying information about the GNSS observations;

at least one PRN word specifying a number of satellites for which observations are included in the message; and

an iono/tropo block providing information about ionosphere and troposphere corrections for the GNSS observations.

18. A message format as in claim 17 wherein the iono/tropo block includes:

a distance measurement of an average vertical ionosphere correction for satellites for which valid data is available; and

a baseline distance for a troposphere correction.

19. A message format as in claim 17 wherein the definition block comprises:

a compression level block specifying a compression level for each of code and carrier data;

an observation suite block indicating a type of code phase used as a reference code per satellite for which data is to be provided; and

a CNR block indicating a number of satellites for which carrier-to-noise data is present.

20. A message format as in claim 19 wherein the definition block further comprises:

an ORB bit, which when active indicates that orbit data is present in the GNSS observation block; and

an SV Cnt block to specify a number of satellites for which at least one of carrier-to-noise and orbit data are present in the GNSS observation block.

21. A message format as in claim 16 wherein the GNSS observation block further comprises:

a definition block specifying information about the GNSS observations; and

the definition block includes a master CTC bit which when active indicates that master continuous tracking counter information is included in the definition block.

22. A message format as in claim 21 wherein the GNSS observation block further comprises, for each satellite:

a minor observation present block which when active indicates information is available about a period of time over which that satellite has been tracked;

a slip bit to designate if a cycle slip has occurred, the slip bit being present only if continuous tracking counter information is not available; and

code signal and carrier signal observations.