Space based augmentation system with hierarchy for determining geographical corrections source

• US 7,110,883 B1
• Filed: 10/04/2004
• Issued: 09/19/2006
• Est. Priority Date: 12/21/2001
• Status: Expired due to Term

• Current Assignee: Garmin Limited
• Original Assignee: Garmin Limited
• Inventors: Barber, Clayton E., Pemble, Cliff
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US10/957,994
• Time in Patent Office: 715 Days
• Field of Search: 701/216, 701220-221, 701/200, 701/207, 701213-215, 342/352, 342/356, 342/357.02, 342/357.04, 342/357.08, 342/357.09, 342/357.15, 342/357.16, 342/358, 342/357.01, 342/357.03, 342/357.06, 455/12.1, 455 131- 133, 455/427, 244/158.1, 244/158.4, 244/158.6, 244/158.8
• US Class Current: 701/214
• CPC Class Codes: G01S 19/074 providing integrity data, e.g. WAAS
• CPC Class Codes: G01S 19/08 providing integrity information, e.g. health of satellites or quality of ephemeris data

Abstract

Systems, devices and methods are provided for determining the appropriate or desired geographical correction source for SBAS corrections. One aspect provided herein is a method. According to one method embodiment, a Space Based Augmentation System (SBAS) correction message is received from a selected SBAS satellite. It is determined whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source and then processing the correction message received therefrom. A second SBAS satellite is selected from which to receive SBAS correction messages upon determining that at least one criterion is not satisfied for using the selected SBAS satellite as a correction source. One example of SBAS is the Wide Area Augmentation System (WAAS) used in North America. Other aspects and embodiments are provided herein.

Claims

1. A method, comprising:

receiving Space Based Augmentation System (SBAS) correction messages from a selected SBAS satellite, wherein SBAS Includes a plurality of precisely-surveyed ground reference stations to receive Global Positioning System (GPS) signals from a plurality of GPS satellites and determine GPS signal errors for the plurality of GPS satellites, and the SBAS further includes at least two SBAS satellites to broadcast correction messages to GPS receivers based on the determined GPS signal errors using a frequency used by the plurality of GPS satellites to send GPS signals to the GPS receivers;

determining whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source including;

determining whether the selected SBAS satellite is sending SBAS correction messages, and

determining whether a differential position can be created from the received SBAS correction messages; and

upon determining that the at least one criterion is not satisfied for using the selected SBAS satellite as a correction source, selecting a second SBAS satellite to be used as a correction source from which to receive SBAS correction messages.

2. The method of claim 1, wherein determining whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source includes determining whether the SBAS correction messages received from the selected SBAS satellite are reliable.

3. The method of claim 1, wherein determining whether a differential position can be created from the received SBAS correction messages is periodically performed.

23. The method of claim 2, wherein determining whether a differential position can be created from the received SBAS correction messages is periodically performed.

4. A method in a global positioning system (GPS) for determining a Wide Area Augmentation System (WAAS) corrections source, comprising:

synchronizing to signals from at least two WAAS satellites;

selecting one WAAS satellite from which to receive WAAS correction messages,

the WAAS correction messages being computed for a plurality of GPS satellites based on GPS signals received from the plurality of GPS satellites at a plurality of precisely-surveyed ground stations;

receiving WAAS correction messages from the selected WAAS satellite;

determining whether at least one criterion is satisfied for using the selected WAAS satellite as a correction source, including determining whether a differential position can be created from the received WAAS correction messages; and

upon determining that the at least one criterion is not satisfied for using the selected WAAS satellite as a correction source, selecting a second WAAS satellite to be used as a correction source from which to receive WAAS correction messages.

5. The method of claim 4, wherein determining whether at least one criterion is satisfied for using the selected WAAS satellite as a correction source includes determining whether the selected WAAS satellite is sending WAAS correction messages.

6. The method of claim 4, wherein determining whether at least one criterion is satisfied for using the selected WAAS satellite as a correction source includes determining whether the WAAS correction messages received from the selected WAAS satellite are reliable.

7. A computer-readable medium having computer-executable instructions, wherein a computer executes the instructions to:

synchronize to signals from at least two Space Based Augmentation System (SBAS) satellites, wherein SBAS Includes a plurality of precisely-surveyed ground reference stations to receive Global Positioning System (GPS) signals from a plurality of GPS satellites and determine GPS signal errors for the plurality of GPS satellites, and the SBAS further includes at least two SBAS satellites to broadcast correction messages to GPS receivers based on the determined GPS signal errors using a frequency used by the plurality of GPS satellites to send GPS signals to the GPS receivers;

select one SBAS satellite from which to receive correction messages;

receive correction messages from the selected SBAS satellite;

determine whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source, including determining whether a differential position can be created from the received SBAS correction messages; and

select a second SBAS satellite to be used as a correction source from which to receive correction messages if the at least one criterion is not satisfied for receiving correction messages from the selected SBAS satellite.

8. The computer-readable medium of claim 7, wherein the computer-executable instructions adapted to determine whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source include computer-executable instructions adapted to determine whether the selected SBAS satellite is sending SBAS correction messages.

9. The computer-readable medium of claim 7, wherein the computer-executable instructions adapted to determine whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source include computer-executable instructions adapted to determine whether the SBAS correction messages received from the selected SBAS satellite are reliable.

10. A data structure embodied on a computer readable medium for use by a Global Positioning System (GPS) receiver device within a Space Based Augmentation System (SBAS) in making SBAS corrections, the SBAS including a plurality of precisely-surveyed ground reference stations to receive Global Positioning System (GPS) signals from a plurality of GPS satellites and determine GPS signal errors for the plurality of GPS satellites, and further including at least two SBAS satellites to broadcast correction messages to GPS receivers based on the determined GPS signal errors using a frequency used by the plurality of GPS satellites to send GPS signals to the GPS receivers, the data structure comprising:

a field representing a variable array of health information for SBAS satellites, wherein the health information for SBAS satellites includes ranging health information, correction health information and broadcast integrity health information;

a field representing a Current SBAS Correction Source (CSCS) variable index; and

a field representing a Potential SBAS Correction Source (PSCS) variable index.

11. The data structure of claim 10, wherein the health information for SBAS satellites includes ranging health information.

12. The data structure of claim 10, wherein the health information for SBAS satellites includes correction health information.

13. The data structure of claim 10, wherein the health information for SBAS satellites includes broadcast integrity health information.

14. A Global Positioning System (GPS) receiver device for use within a Space Based Augmentation System (SBAS) in which the SBAS includes a plurality of precisely-surveyed ground reference stations to receive GPS signals from a plurality of GPS satellites and determine GPS signal errors for the plurality of GPS satellites, and further includes at least two SBAS satellites to broadcast correction messages to GPS receivers based on the determined GPS signal errors using a frequency used by the plurality of GPS satellites to send GPS signals to the GPS receivers, the GPS receiver device comprising:

a processor;

a memory to communicate to the processor; and

a GPS receiver to receive GPS signals and SBAS correction signals, and to communicate with the processor,

wherein the processor and the memory cooperate to determine a desired SBAS correction source based on the SBAS correction signals using at least one predetermined criterion, and

wherein the at least one predetermined criterion includes a stability-threshold criterion for verifying that the desired SBAS correction source is sending reliable correction messages within a stability threshold.

15. The device of claim 14, wherein the GPS receiver device comprises a portable GPS receiver device.

16. The device of claim 15, wherein the GPS receiver device comprises a personal digital assistant (PDA).

17. The device of claim 15, wherein the GPS receiver device comprises a wireless communication device.

18. The device of claim 14, wherein the at least one predetermined criterion includes an SBAS-correction-sent criterion for verifying that the desired SBAS correction source is sending correction messages.

19. The device of claim 14, wherein the at least one predetermined criterion includes an SBAS-correction-reliable criterion for verifying that the desired SBAS correction source is sending reliable correction messages.

20. The device of claim 14, wherein the at least one predetermined criterion includes a differential-position-calculation-capable criterion for verifying that the desired SBAS correction source is sending reliable correction messages from which a differential position is capable of being computed.

21. A method, comprising:

receiving Space Based Augmentation System (SBAS) correction messages from a selected SBAS satellite, wherein SBAS includes a plurality of precisely-surveyed ground reference stations to receive Global Positioning System (GPS) signals from a plurality of GPS satellites and determine GPS signal errors for the plurality of GPS satellites, and the SBAS further includes at least two SBAS satellites to broadcast correction messages to GPS receivers based on the determined GPS signal errors using a frequency used by the plurality of GPS satellites to send GPS signals to the GPS receives;

determining whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source, including—

determining whether the SBAS correction messages received from the selected SBAS satellite are reliable, and

determining whether a differential position can be created from the received SBAS correction messages; and

upon determining that the at least one criterion is not satisfied for using the selected SBAS satellite as a correction source, selecting a second SBAS satellite to be used as a correction source from which to receive SBAS correction messages.

22. The method of claim 21, wherein determining whether a differential position can be created from the received SBAS correction messages is periodically performed.

24. A Global Positioning System (GPS) receiver device for use within a Space Based Augmentation System (SBAS) in which the SBAS includes a plurality of precisely-surveyed ground reference stations to receive GPS signals from a plurality of GPS satellites and determine GPS signal errors for the plurality of GPS satellites, and further includes at least two SBAS satellites to broadcast correction messages to GPS receivers based on the determined GPS signal errors using a frequency used by the plurality of GPS satellites to send GPS signals to the GPS receivers, the GPS receiver device comprising:

a processor;

a memory to communicate to the processor; and

a GPS receiver to receive GPS signals and SBAS correction signals, and to communicate with the processor,

wherein the processor and the memory cooperate to determine a desired SBAS correction source based on the SBAS correction signals using at least one predetermined criterion, and

wherein the at least one predetermined criterion includes a differential-position-calculation-capable criterion for verifying that the desired SBAS correction source is sending reliable correction messages from which a differential position is capable of being computed.

28. The device of claim 24, wherein the at least one predetermined criterion includes an SBAS-correction-sent criterion for verifying that the desired SBAS correction source is sending correction messages.

29. The device of claim 24, wherein the at least one predetermined criterion includes an SBA-correction-reliable criterion for verifying that the desired SBAS correction source is sending reliable correction messages.

25. The device of claim, wherein the GPS receiver device comprises a portable GPS receiver device.

26. The device of claim 25 wherein the GPS receiver device comprises a personal digital assistant (PDA).

27. The device of claim 25, wherein the GPS receiver device comprises a wireless communication device.