Geolocation communications method during visibility between an earth-orbit satellite and a transmitter and receiver

• US 6,157,896 A
• Filed: 12/30/1996
• Issued: 12/05/2000
• Est. Priority Date: 12/30/1996
• Status: Expired due to Term

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Castles, Milford Pike, Moryl, James Andrew, Boyd, Austin Walker Jr.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US08/775,086
• Time in Patent Office: 1,436 Days
• Field of Search: 702/95, 701/207, 701/213-215, 342/357, 342/357.1, 342/367, 342/357.05, 342/357.02, 455/427, 455/428, 455/440, 455/456
• US Class Current: 702/95
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: H04B 7/18552 using a telephonic control signal and a second ranging satellite determining absolute distances from a plurality of spaced points of known location G01S5/14

Abstract

A method for determining the geolocation of an object such as a vehicle traversing the earth'"'"'s surface or airborne thereabove includes employing a device which is capable of operating autonomously to transmit signals to a selected low earth orbit (LEO) satellite for relay to a receiving station whose position is known, identifying the device and its geolocation, speed, altitude and/or heading. The device includes a microcomputer which operates a Global Positioning System (GPS) receiver for receiving GPS signals to identify the device geolocation and the precise time. A nonvolatile memory on board the device stores LEO satellite ephemeris data, satellite operational and message formatting parameters, LEO satellite visibility footprint data and visibility contour information for the device caused by obstacles which are permanently or temporarily in proximity to the device during deployment and which block transmission of signals between the device and the LEO satellite, depending on relative positions. Geolocation information is transmitted to a LEO satellite for relay to the receiving station after calculation of covisibility of the satellite with the receiving station and the transmitter antenna for the device, taking into account the device visibility contour and heading. The device transmitter antenna may have a steering mechanism for causing the antenna to be aimed at a predetermined azimuth and elevation wherein the transmitted signals will be intercepted by the LEO satellite.

Claims

1. A method for communicating geolocation and messages from a device to a receiving station, comprising the steps of:

a) receiving signals by the device from a position determining system;

b) determining a geolocation, a speed value, and a heading value of the device from the received position determining signals;

c) determining automatically and autonomously a visibility reduction based on proximate deployment constraints stored in the device and the device heading value;

d) determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station by using a current time, the device geolocation, the receiving station geolocation, the visibility reduction, and low earth orbit satellite ephemeris data stored in the device; and

e) transmitting the geolocation, the speed value, the heading value, and messages from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station for relay to the receiving station by the low earth orbit satellite.

2. A method according to claim 1, wherein the position determining system is the NAVSTAR/Global Positioning System.

3. A method according to claim 1, wherein the step of determining a geolocation comprises the steps of autonomously determining a longitude value and a latitude value of a position of the device and simultaneously and autonomously determining a time value taken at that position of the device.

4. A method according to claim 1, wherein the step of determining a geolocation comprises the steps of autonomously determining a three-dimensional value of a position of the device and simultaneously and autonomously determining a time value taken at that position of the device.

5. A method according to claim 1, wherein the step of determining automatically and autonomously a visibility reduction comprises the steps of autonomously determining a heading value of the device and deployment constraint elevation angles and associated deployment constraint azimuth angles stored in the device.

6. A method according to claim 1, wherein the step of determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station, and the step of transmitting the geolocation comprise the steps of:

a) determining a visibility time duration when each of a plurality of low earth orbit satellites is visible to both the device and the receiving station;

b) selecting a low earth orbit satellite having a selected visibility time duration from the plurality of low earth orbit satellites; and

c) transmitting the geolocation, the speed value, the heading value, and messages from the device to the selected low earth orbit satellite during the selected visibility time duration when the selected low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

7. A method according to claim 6, wherein the step of selecting a low earth orbit satellite comprises the steps of:

a) comparing the visibility time duration for each of the plurality of low earth orbit satellites; and

b) selecting a low earth orbit satellite having a selected visibility time duration and a shortest time interval between a present time and a beginning time of the selected visibility time duration.

8. A method according to claim 6, wherein the step of determining a visibility time duration when each of a plurality of low earth orbit satellites is visible to both the device and the receiving station, comprises the step of determining a time duration for each of a plurality of earth orbit satellites when:

a) visibility between the device and the low earth orbit satellite is not reduced due to proximate deployment constraints;

b) an elevation angle of a low earth orbit satellite is greater than a mask angle based on a predicted position of the device; and

c) a visibility footprint of the low earth orbit satellite indicates a visibility time duration when both the device and the receiving station are contained within the visibility footprint.

9. A method according to claim 1, wherein the step of determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station, and the step of transmitting the geolocation comprise the steps of:

a) determining a visibility time duration when each of a plurality of low earth orbit satellites is visible to both the device and the receiving station;

b) selecting more than one low earth orbit satellite having selected visibility time durations from the plurality of low earth orbit satellites; and

c) transmitting the geolocation, the speed value, the heading value, and messages from the device to the selected low earth orbit satellites during the selected visibility time durations when the low earth orbit satellites are visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

10. A method according to claim 1, wherein the step of determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station, and the step of transmitting the geolocation comprise the steps of:

a) determining a maximum elevation angle and associated azimuth angle for each of a plurality of low earth orbit satellites based on the device geolocation and satellite ephemeris data stored in the device;

b) comparing the maximum elevation angle for each low earth orbit satellite with a device mask angle for each satellite;

c) comparing the maximum elevation angle and associated azimuth angle for each low earth orbit satellite with deployment constraint elevation angles and associated deployment constraint azimuth angles stored in the device;

d) identifying each satellite having a maximum elevation angle that exceeds the device mask angle and deployment constraint elevation angles at corresponding azimuth angles;

e) selecting identified satellites having a maximum elevation angle that exceeds the device mask angle and the deployment constraint elevation angles, and having a visibility footprint that provides visibility to both the device and the receiving station;

f) determining a selected visibility time duration for each selected satellite having a maximum elevation angle that exceeds the device mask angle and the deployment constraint elevation angles, and when the satellite visibility footprint provides visibility to both the device and receiving station; and

g) transmitting the geolocation, the speed value, the heading value, and messages from the device to a predetermined number of the selected low earth orbit satellites during the selected visibility time duration for each of the predetermined number of selected low earth orbit satellites.

11. A method according to claim 10, wherein the step of transmitting the geolocation comprises transmitting the geolocation, the speed value, the heading value, and messages from the device to a predetermined number of the selected low earth orbit satellites when each of the predetermined number of selected low earth orbit satellites is at its maximum elevation angle.

12. A method according to claim 10, wherein the step of selecting identified satellites further comprises selecting identified satellites having a shortest time interval between a present time and a beginning time of an identified satellite selected visibility time duration.

13. A method according to claim 10, wherein the step of transmitting the geolocation comprises the steps of:

a) steering an antenna connected to the device to a maximum elevation angle and an azimuth for a selected low earth orbit satellite; and

b) transmitting the geolocation, the speed value, the heading value, and messages from the device to the selected low earth orbit satellite during the selected satellite selected visibility time.

14. A method according to claim 1, wherein the step of transmitting the geolocation comprises transmitting the geolocation, the speed value, the heading value, and messages more than once from the device to the low earth orbit satellite when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

15. A method according to claim 1, wherein the step of transmitting the geolocation comprises transmitting the geolocation and messages at least once during a first half of the visibility time duration, and at least once during a second half of the visibility time duration.

16. A method according to claim 1, wherein the step of receiving signals by the device comprises:

a) receiving signals by a receiver in the device from a position determining system at a set of predetermined times; and

b) reducing power to the receiver at times between the set of predetermined times.

17. A method according to claim 1, wherein the step of transmitting the geolocation comprises:

a) selecting a transmitter power level;

b) transmitting the geolocation, the speed value, the heading value, and messages by a transmitter in the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station; and

c) reducing the transmitter power level at times the transmitter is not transmitting the geolocation and messages.

18. A method according to claim 1, further comprising the step of preprogramming the device with operational parameters.

19. A method according to claim 18, wherein the operational parameters comprise ephemeris data, operating area information, deployment constraint elevation angles and associated azimuth angles, mask angles, identity codes, and transmission data formats for a plurality of low earth orbit satellites.

20. A method according to claim 18, wherein the preprogramming step is performed by downloading the operational parameters to the device from a computer connected to a connector positioned on the device.

21. A method according to claim 1, wherein the step of transmitting the geolocation data further comprises selecting a data rate, modulation format, data format, transmission frequency and signal transmission power level for compatibility with a selected constellation low earth orbit satellites.

22. A method according to claim 1, wherein the step of receiving signals from a position determining system is performed by a receive antenna and the step of transmitting the geolocation is performed by a transmit antenna.

23. A method according to claim 1, wherein the step of receiving signals from a position determining system comprises receiving signals from at least three earth orbit position determining satellites.

24. A method according to claim 1, wherein the receiving station comprises more than one receiving station.

25. A method according to claim 1, wherein the messages includes voice and data information.

26. A method according to claim 1, wherein proximate deployment constraints of the device are spatial areas, defined in terms of deployment constraint elevation angles and deployment constraint azimuth angles, wherein one or more obstacles are present in a fixed positional relationship with respect to the device that will block transmission of geolocation, the speed value, the heading value, and messages from the device to the low earth orbit satellite.

27. A method according to claim 1, wherein the deployment constraints are selected from the group consisting of natural structures, manmade structures, strong electric fields, and strong magnetic fields.

28. A method according to claim 1, wherein the device is deployed on a mobile object.

59. A method according to claim 1, wherein there is no visibility reduction based on proximate deployment constraints stored in the device and the device heading value.

29. A device for communicating geolocation and messages to a receiving station, comprising:

a) means for receiving signals by the device from a position determining system;

b) means for determining a geolocation, a speed value, and a heading value of the device from the received position determining signals;

c) means for determining automatically and autonomously a visibility reduction based on proximate deployment constraints stored in the device and the device heading value;

d) means for determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station by using a current time, the device geolocation, the receiving station geolocation, the visibility reduction, and low earth orbit satellite ephemeris data stored in the device; and

e) means for transmitting the geolocation and messages from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

30. A device according to claim 29, wherein the position determining system is the NAVSTAR/Global Positioning System.

31. A device according to claim 29, wherein the receiving station includes a means for displaying a track depicting the geographical movement of the device.

32. A device according to claim 29, wherein the means for receiving signals from a position determining system comprises an omnidirectional receive antenna connected to a geolocation data and time signal receiver.

33. A device according to claim 32, further comprising a power management means for reducing power to the geolocation data and time receiver at time durations when the signals from the position determining system are not required.

34. A device according to claim 29, wherein the means for determining a geolocation from the received position determining signals comprises:

a) a microprocessor connected to a geolocation data and time signal receiver;

b) a real time clock connected to the microprocessor;

c) a nonvolatile memory connected to the microprocessor for storing control program software for computing geolocation; and

d) a computer program stored in the nonvolatile memory for controlling the microprocessor to compute a geolocation.

35. A device according to claim 34, wherein the computer program controls the microprocessor for autonomously computing a longitude value, a latitude value and a time value of the position of the device.

36. A device according to claim 34, wherein the computer program controls the microprocessor for computing a speed value and a heading value of the device motion.

37. A device according to claim 29, wherein the means for determining a visibility time duration comprises:

a) a microprocessor;

b) a nonvolatile memory connected to the microprocessor for storing control program software, low earth orbit satellite ephemeris data, proximate deployment constraint data, and operating area information;

c) a geolocation stored in memory; and

d) a computer program stored in nonvolatile memory for controlling the microprocessor to compute a visibility time duration.

38. A device according to claim 37, wherein the computer program controls the microprocessor for computing the visibility time duration using a present time, the device geolocation, the proximate deployment constraint data, a receiving station geolocation, and low earth orbit ephemeris data stored in nonvolatile memory.

39. A device according to claim 29, wherein the computer program controls the microprocessor for determining a visibility time duration when an elevation angle of a low earth orbit satellite is greater than a mask angle and deployment constraint elevation angles, and a visibility footprint of the low earth orbit satellite contains both the device and the receiving station.

40. A device according to claim 29, wherein the means for transmitting the geolocation comprises:

a) a satellite transmitter connected to a microprocessor; and

b) a transmit antenna connected to the satellite transmitter.

41. A device according to claim 40, further comprising an antenna steering means connected to the microprocessor and the transmit antenna for steering the transmit antenna to an azimuth angle and an elevation angle.

42. A device according to claim 40, wherein the transmit antenna is an omni-directional antenna.

43. A device according to claim 40, further comprising a power management means for reducing power to the satellite transmitter at times the transmitter is not transmitting.

44. A device according to claim 40, further comprising a means for controlling a data rate, modulation format, data format, transmission frequency and signal transmission power level of the satellite transmitter by the microprocessor.

45. A device according to claim 29, further comprising a message display unit, a power source and an input/output connector.

46. A device according to claim 29, further comprising a means for preprogramming the device by downloading operational parameters to the device from a computer connected to a connector positioned on the device.

60. A device according to claim 29, wherein there is no visibility reduction based on proximate deployment constraints stored in the device and the device heading value.

47. A system for communicating geolocation and messages from a device to a receiving station, comprising:

a) a position determining system for transmitting position determining signals;

b) a device for;

1) receiving the position determining signals;

2) determining a geolocation, a speed value, and a heading value of the device;

3) determining automatically and autonomously a visibility reduction based on proximate deployment constraints stored in the device and the device heading value;

4) determining a visibility time duration when a low earth orbit satellite is visible to both the device and a receiving station by using a current time, the device geolocation, the receiving station geolocation, the visibility reduction, and low earth orbit satellite ephemeris data stored in the device; and

5) transmitting geolocation, the speed value, the heading value, and messages from the device to a low earth orbit satellite during the visibility time duration;

c) a low earth orbit satellite for receiving the geolocation, the speed value, the heading value, and messages from the device and transmitting such information to a receiving station; and

d) a receiving station for receiving the geolocation, the speed value, the heading value, and messages, processing such information, and displaying such information.

48. A system according to claim 47, wherein the position determining system is the NAVSTAR/Global Positioning System.

49. A system according to claim 47, wherein determining geolocation comprises determining a longitude value, a latitude value, and an associated time value of the device.

50. A system according to claim 47, wherein determining geolocation comprises determining a three-dimensional value of the position and an associated time value of the device.

51. A system according to claim 47, wherein determining a visibility time duration is based on low earth orbit satellite ephemeris data, mask angles, proximate deployment constraint elevation angles and associated azimuth angles, maximum elevation angle and associated azimuth angle, satellite visibility footprint, and receiving station location.

52. A system according to claim 47, wherein the low earth orbit satellite comprises a receiver and a transmitter for relaying geolocation and messages from the device to the receiving station.

61. A system according to claim 47, wherein there is no visibility reduction based on proximate deployment constraints stored in the device and the device heading value.

53. A microprocessor-implemented computer program for communicating geolocation and messages from a device to a receiving station, comprising the steps of:

a) receiving signals by the device from a position determining system by controlling a geolocation data and time signal receiver;

b) determining a current geolocation, a speed value, and a heading value of the device from the received position determining signals;

c) determining automatically and autonomously a visibility reduction based on proximate deployment constraints stored in the device and the device heading;

d) determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station by using a current time, the device geolocation, the receiving station geolocation, the visibility reduction, and low earth orbit satellite ephemeris data stored in the device; and

e) transmitting the geolocation, the speed value, the heading value, and messages from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station, by controlling transmission of a device satellite transmitter.

54. A microprocessor-implemented computer program according to claim 53, wherein the step of receiving signals by the device by controlling a geolocation data and time signal receiver comprises the steps of:

a) applying power to the receiver;

b) activating the receiver for receiving position determining signals;

c) acquiring position determining signals;

d) storing the position determining signals in a memory; and

e) reducing power to the receiver.

55. A microprocessor-implemented computer program according to claim 53, wherein the step of determining a geolocation of the device comprises the steps of:

a) accessing the position determining signals from the memory;

b) computing a geolocation from the position determining signals comprising a longitude value, a latitude value, and a time value; and

c) storing the geolocation in the memory.

56. A microprocessor-implemented computer program according to claim 53, wherein the step of determining a visibility time duration comprises the steps of:

a) computing a maximum elevation angle and an associated azimuth angle for each of a plurality of low earth orbit satellites based on the device geolocation and satellite ephemeris data stored in memory;

b) comparing the maximum elevation angle for each low earth orbit satellite with a device mask angle for each satellite;

c) comparing the maximum elevation angle and the associated azimuth angle for each low earth orbit satellite with deployment constraint elevation angles and associated deployment constraint azimuth angles stored in memory;

d) identifying each satellite having a maximum elevation angle that exceeds the device mask angle and deployment constraint elevation angles at corresponding azimuth angles;

e) selecting identified satellites having a maximum elevation angle that exceeds the mask angle and the deployment constraint elevation angles, and having a visibility footprint that provides visibility to both the device and the receiving station; and

f) determining a selected visibility time duration for a selected satellite having a maximum elevation angle that exceeds the mask angle and the deployment constraint elevation angles, and when the visibility footprint of the selected satellite provides visibility to both the device and the receiving station.

57. A microprocessor-implemented computer program according to claim 53, wherein the step of transmitting the geolocation and messages from the device to the low earth orbit satellite by controlling transmission of a device satellite transmitter comprises the steps of:

a) applying power to the device satellite transmitter;

b) setting transmission parameters of the device satellite transmitter comprising data rate, modulation format, data format, transmission frequency, and signal transmission power level;

c) transmitting the geolocation and messages from the device satellite transmitter to the low earth orbit satellite during the visibility time; and

d) reducing power to the device satellite transmitter.

58. Computer readable medium containing instructions for performing the steps in the computer program as recited in claim 53.

62. A microprocessor-implemented computer program according to claim 53, wherein there is no visibility reduction based on proximate deployment constraints stored in the device and the device heading.