Position location using terrestrial digital video broadcast television signals

• US 7,126,536 B2
• Filed: 08/17/2001
• Issued: 10/24/2006
• Est. Priority Date: 02/02/2001
• Status: Active Grant

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: Rosum Corporation (Liberty Broadband Corp.)
• Inventors: Rabinowitz, Matthew, Spilker, Jr., James J
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/932,010
• Publication Number:
  US 20020144294A1
• Time in Patent Office: 1,894 Days
• Field of Search: 342/357.01, 342/357.06, 342/453, 342/463, 342/464
• US Class Current: 342/464
• CPC Class Codes: A63F 2300/205 for detecting the geographical location of the game platform
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/0054 of actual mobile position, i.e. position calculation on base station
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/01 Determining conditions which influence positioning, e.g. radio environment, state of motion or energy consumption
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/02526 using non-dedicated equipment, e.g. user equipment or crowd-sourcing
• CPC Class Codes: G01S 5/145 Using a supplementary range measurement, e.g. based on pseudo-range measurements
• CPC Class Codes: H04N 21/25841 involving the geographical location of the client retrieval from the Internet by querying based on geographical locations G06F16/9537; arrangements for identifying locations of receiving stations in broadcast systems H04H60/51; location of the user terminal in data switching networks H04L67/52; services making use of the location of users or terminals in wireless networks H04W4/02; locating users or terminals in wireless networks H04W64/00
• CPC Class Codes: H04N 21/2662 Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
• CPC Class Codes: H04N 21/2668 Creating a channel for a dedicated end-user group, e.g. insertion of targeted commercials based on end-user profiles information retrieval from the Internet by querying with filtering and personalisation G06F16/9535; arrangements for replacing or switching information during the broadcast H04H20/10; push services over packet-switching network H04L12/1859; adaptation of message content in packet-switching networks H04L51/063
• CPC Class Codes: H04N 21/41422 located in transportation means, e.g. personal vehicle arrangements specially adapted for transportation systems in broadcast systems H04H20/62
• CPC Class Codes: H04N 21/615 Signal processing at physical level signal processing in analog two-way television systems H04N7/173
• CPC Class Codes: H04N 21/8126 involving additional data, e.g. news, sports, stocks, weather forecasts

Abstract

A method and computer program product for determining the position of a user terminal includes receiving at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting-Terrestrial (DVB-T) signal; determining a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals based on a known component in the DTV signals; and determining a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

Claims

1. A method for determining the position of a user terminal, comprising:

receiving at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal;

determining a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals; and

determining a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

2. The method of claim 1, wherein determining a position of the user terminal comprises:

adjusting the pseudo-ranges based on a difference between a transmitter clock at one of the DTV transmitters and a known time reference; and

determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

3. The method of claim 1, wherein the known component is a scattered pilot carrier.

4. The method of claim 1, wherein determining a position of the user terminal comprises:

determining an offset between a local time reference in the user terminal and a master time reference; and

determining the position of the user terminal based on the pseudo-ranges, the location of each of the DTV transmitters, and the offset.

5. The method of claim 4, further comprising:

determining a subsequent position of the user terminal using the offset.

6. The method of claim 1, wherein determining a pseudo-range comprises:

storing a portion of each of the DTV signals; and

subsequently correlating each of the stored portions and a signal generated by the user terminal to produce the pseudo-ranges.

7. The method of claim 1, wherein determining a pseudo-range comprises:

correlating each of the DTV signals with a signal generated by the user terminal as the DTV signals are received to produce the pseudo-ranges.

8. The method of claim 1, wherein determining a position of the user terminal comprises:

determining a general geographic area within which the user terminal is located; and

determining the position of the user terminal based on the pseudo-ranges and the general geographic area.

9. The method of claim 8, wherein the general geographic area is a footprint of an additional transmitter communicably linked to the user terminal.

10. The method of claim 1, wherein determining a position of the user terminal comprises:

determining a tropospheric propagation velocity in a vicinity of the user terminal;

adjusting the value of each pseudo-range based on the tropospheric propagation velocity; and

determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

11. The method of claim 1, wherein determining a position of the user terminal comprises:

adjusting each pseudo-range based on a terrain elevation in a vicinity of the user terminal; and

determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

12. The method of claim 1, further comprising:

selecting the DTV signals based on an identity of an additional transmitter communicably linked to the user terminal and a stored table correlating the additional transmitter and the received DTV broadcast signals.

13. The method of claim 1, further comprising:

accepting a location input from a user; and

selecting the DTV signals based on the location input.

14. The method of claim 1, further comprising:

scanning available DTV signals to assemble a fingerprint of the location; and

selecting the DTV broadcast signals used to determine the pseudo-ranges based on the fingerprint and a stored table that matches known fingerprints with known locations.

15. The method of claim 1, further comprising:

using receiver autonomous integrity monitoring (RAIM) to check the integrity of each pseudo-range based on redundant pseudo-ranges from the DTV transmitters.

16. A method for determining the position of a user terminal, comprising:

receiving at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal;

determining a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals; and

transmitting the pseudo-ranges to a location server configured to determine a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

17. The method of claim 16, wherein determining a pseudo-range comprises:

determining a time of transmission from one of the DTV transmitters of a known component of the DTV broadcast signal;

determining a time of reception at the user terminal of the known component; and

determining the difference between the time of transmission and the time of reception.

18. The method of claim 16, wherein the known component is a scattered pilot carrier.

19. The method of claim 16, wherein determining a pseudo-range comprises:

storing a portion of each of the DTV signals; and

subsequently correlating each of the stored portions and a signal generated by the user terminal to produce the pseudo-ranges.

20. The method of claim 16, wherein determining a pseudo-range comprises:

correlating each of the DTV signals with a signal generated by the user terminal as the DTV signals are received to produce the pseudo-ranges.

21. A method for determining the position of a user terminal, comprising:

receiving a plurality of pseudo-ranges from a user terminal, each pseudo-range determined between the user terminal and one of a plurality of DTV transmitters based on DTV signals broadcast by the DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal, and wherein the pseudo-ranges are determined based on a known component in the DVB-T signals; and

determining a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

22. The method of claim 21, wherein determining a position of the user terminal comprises:

adjusting the pseudo-ranges based on a difference between a transmitter clock at one of the DTV transmitters and a known time reference; and

determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

23. The method of claim 21, wherein the known component is a scattered pilot carrier.

24. The method of claim 21, wherein determining a position of the user terminal comprises:

determining an offset between a local time reference in the user terminal and a master time reference; and

determining the position of the user terminal based on the pseudo-ranges, the location of each of the DTV transmitters, and the offset.

25. The method of claim 24, further comprising:

determining a subsequent position of the user terminal using the offset.

26. The method of claim 21, wherein determining a position of the user terminal comprises:

determining a general geographic area within which the user terminal is located; and

determining the position of the user terminal based on the pseudo-ranges and the general geographic area.

27. The method of claim 26, wherein the general geographic area is a footprint of an additional transmitter communicably linked to the user terminal.

28. The method of claim 21, wherein determining a position of the user terminal comprises:

determining a tropospheric propagation velocity in a vicinity of the user terminal;

adjusting the value of each pseudo-range based on the tropospheric propagation velocity; and

determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

29. The method of claim 21, wherein determining a position of the user terminal comprises:

adjusting each pseudo-range based on the terrain elevation in the vicinity of the user terminal; and

determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

30. An apparatus for determining the position of a user terminal, comprising:

means for receiving at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal;

means for determining a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals; and

means for determining a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

31. The apparatus of claim 30, wherein means for determining a position of the user terminal comprises:

means for adjusting the pseudo-ranges based on a difference between a transmitter clock at one of the DTV transmitters and a known time reference; and

means for determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

32. The apparatus of claim 31, wherein the known component is a scattered pilot carrier.

33. The apparatus of claim 30, wherein means for determining a position of the user terminal comprises:

means for determining an offset between a local time reference in the user terminal and a master time reference; and

means for determining the position of the user terminal based on the pseudo-ranges, the location of each of the DTV transmitters, and the offset.

34. The apparatus of claim 33, further comprising:

means for determining a subsequent position of the user terminal using the offset.

35. The apparatus of claim 30, wherein means for determining a pseudo-range comprises:

means for storing a portion of each of the DTV signals; and

means for subsequently correlating each of the stored portions and a signal generated by the user terminal to produce the pseudo-ranges.

36. The apparatus of claim 30, wherein means for determining a pseudo-range comprises:

means for correlating each of the DTV signals with a signal generated by the user terminal as the DTV signals are received to produce the pseudo-ranges.

37. The apparatus of claim 30, wherein means for determining a position of the user terminal comprises:

means for determining a general geographic area within which the user terminal is located; and

means for determining the position of the user terminal based on the pseudo-ranges and the general geographic area.

38. The apparatus of claim 37, wherein the general geographic area is a footprint of an additional transmitter communicably linked to the user terminal.

39. The apparatus of claim 30, wherein means for determining a position of the user terminal comprises:

means for determining a tropospheric propagation velocity in the vicinity of the user terminal;

means for adjusting the value of each pseudo-range based on the tropospheric propagation velocity; and

means for determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

40. The apparatus of claim 30, wherein means for determining a position of the user terminal comprises:

means for adjusting each pseudo-range based on a terrain elevation in a vicinity of the user terminal; and

means for determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

41. The apparatus of claim 30, further comprising:

means for selecting the DTV signals based on an identity of an additional transmitter communicably linked to the user terminal and a stored table correlating the additional transmitter and the received DTV broadcast signals.

42. The apparatus of claim 30, further comprising:

means for accepting a location input from a user; and

means for selecting the DTV signals based on the location input.

43. The apparatus of claim 30, further comprising:

means for scanning available DTV signals to assemble a fingerprint of the location; and

means for selecting the DTV broadcast signals used to determine the pseudo-ranges based on the fingerprint and a stored table that matches known fingerprints with known locations.

44. The apparatus of claim 30, further comprising:

means for using receiver autonomous integrity monitoring (RAIM) to check the integrity of each pseudo-range based on redundant pseudo-ranges from the DTV transmitters.

45. An apparatus for determining the position of a user terminal, comprising:

means for receiving at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal;

means for determining a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals; and

means for transmitting the pseudo-ranges to a location server configured to determine a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

46. The apparatus of claim 45, wherein means for determining a pseudo-range comprises:

means for determining a time of transmission from one of the DTV transmitters of a component of the DTV broadcast signal;

means for determining a time of reception at the user terminal of the component; and

means for determining the difference between the time of transmission and the time of reception.

47. The apparatus of claim 45, wherein the component is a scattered pilot carrier.

48. The apparatus of claim 45, wherein means for determining a pseudo-range comprises:

means for storing a portion of each of the DTV signals; and

means for subsequently correlating each of the stored portions and a signal generated by the user terminal to produce the pseudo-ranges.

49. The apparatus of claim 45, wherein means for determining a pseudo-range comprises:

means for correlating each of the DTV signals with a signal generated by the user terminal as the DTV signals are received to produce the pseudo-ranges.

50. An apparatus for determining the position of a user terminal, comprising:

means for receiving a plurality of pseudo-ranges from a user terminal, each pseudo-range determined between the user terminal and one of a plurality of DTV transmitters based on DTV signals broadcast by the DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal, and wherein the pseudo-ranges are determined based on a known component in the DTV signals; and

means for determining a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

51. The apparatus of claim 50, wherein means for determining a position of the user terminal comprises:

means for adjusting the pseudo-ranges based on a difference between a transmitter clock at one of the DTV transmitters and a known time reference; and

means for determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

52. The apparatus of claim 50, wherein the known component is a scattered pilot carrier.

53. The apparatus of claim 50, wherein means for determining a position of the user terminal comprises:

means for determining an offset between a local time reference in the user terminal and a master time reference; and

means for determining the position of the user terminal based on the pseudo-ranges, the location of each of the DTV transmitters, and the offset.

54. The apparatus of claim 53, further comprising:

means for determining a subsequent position of the user terminal using the offset.

55. The apparatus of claim 50, wherein means for determining a position of the user terminal comprises:

means for determining a general geographic area within which the user terminal is located; and

means for determining the position of the user terminal based on the pseudo-ranges and the general geographic area.

56. The apparatus of claim 55, wherein the general geographic area is a footprint of an additional transmitter communicably linked to the user terminal.

57. The apparatus of claim 50, wherein means for determining a position of the user terminal comprises:

means for determining a tropospheric propagation velocity in a vicinity of the user terminal;

means for adjusting the value of each pseudo-range based on the tropospheric propagation velocity; and

means for determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

58. The apparatus of claim 50, wherein means for determining a position of the user terminal comprises:

means for adjusting each pseudo-range based on the terrain elevation in the vicinity of the user terminal; and

means for determining the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

59. A computer program product, tangibly stored on a computer-readable medium, for determining the position of a user terminal, comprising instructions operable to cause a programmable processor to:

receive at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal;

determine a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals; and

determine a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

60. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

adjust the pseudo-ranges based on a difference between a transmitter clock at one of the DTV transmitters and a known time reference; and

determine the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

61. The computer program product of claim 59, wherein the known component is a scattered pilot carrier.

62. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

determine an offset between a local time reference in the user terminal and a master time reference; and

determine the position of the user terminal based on the pseudo-ranges, the location of each of the DTV transmitters, and the offset.

63. The computer program product of claim 62, further comprising instructions operable to cause a programmable processor to:

determine a subsequent position of the user terminal using the offset.

64. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a pseudo-range comprise instructions operable to cause a programmable processor to:

store a portion of each of the DTV signals; and

subsequently correlate each of the stored portions and a signal generated by the user terminal to produce the pseudo-ranges.

65. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a pseudo-range comprise instructions operable to cause a programmable processor to:

correlate each of the DTV signals with a signal generated by the user terminal as the DTV signals are received to produce the pseudo-ranges.

66. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

determine a general geographic area within which the user terminal is located; and

determine the position of the user terminal based on the pseudo-ranges and the general geographic area.

67. The computer program product of claim 66, wherein the general geographic area is a footprint of an additional transmitter communicably linked to the user terminal.

68. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to

determine a tropospheric propagation velocity in a vicinity of the user terminal;

adjust the value of each pseudo-range based on the tropospheric propagation velocity; and

determine the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

69. The computer program product of claim 59, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

adjust each pseudo-range based on the terrain elevation in the vicinity of the user terminal; and

determine the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

70. The computer program product of claim 59, further comprising instructions operable to cause a programmable processor to:

select the DTV signals based on an identity of an additional transmitter communicably linked to the user terminal and a stored table correlating the additional transmitter and the received DTV broadcast signals.

71. The computer program product of claim 59, further comprising instructions operable to cause a programmable processor to:

accept a location input from a user; and

select the DTV signals based on the location input.

72. The computer program product of claim 59, further comprising instructions operable to cause a programmable processor to:

scan available DTV signals to assemble a fingerprint of the location; and

select the DTV broadcast signals used to determine the pseudo-ranges based on the fingerprint and a stored table that matches known fingerprints with known locations.

73. The computer program product of claim 59, further comprising instructions operable to cause a programmable processor to:

use receiver autonomous integrity monitoring (RAIM) to check the integrity of each pseudo-range based on redundant pseudo-ranges from the DTV transmitters.

74. A computer program product, tangibly stored on a computer-readable medium, for determining the position of a user terminal, comprising instructions operable to cause a programmable processor to:

receive at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal;

determine a pseudo-range between the user terminal and each DTV transmitter based on a known component in the DTV broadcast signals; and

transmit the pseudo-ranges to a location server configured to determine a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

75. The computer program product of claim 74, wherein instructions operable to cause a programmable processor to determine a pseudo-range comprise instructions operable to cause a programmable processor to:

determine a time of transmission from one of the DTV transmitters of a component of the DTV broadcast signal;

determine a time of reception at the user terminal of the component; and

determining the difference between the time of transmission and the time of reception.

76. The computer program product of claim 74, wherein the component is a scattered pilot carrier.

77. The computer program product of claim 74, wherein instructions operable to cause a programmable processor to determine a pseudo-range comprise instructions operable to cause a programmable processor to:

store a portion of each of the DTV signals; and

subsequently correlate each of the stored portions and a signal generated by the user terminal to produce the pseudo-ranges.

78. The computer program product of claim 74, wherein instructions operable to cause a programmable processor to determine a pseudo-range comprise instructions operable to cause a programmable processor to:

correlate each of the DTV signals with a signal generated by the user terminal as the DTV signals are received to produce the pseudo-ranges.

79. A computer program product, tangibly stored on a computer-readable medium, for determining the position of a user terminal, comprising instructions operable to cause a programmable processor to:

receive a plurality of pseudo-ranges from a user terminal, each pseudo-range determined between the user terminal and one of a plurality of DTV transmitters based on DTV signals broadcast by the DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting—

Terrestrial (DVB-T) signal, and wherein the pseudo-ranges are determined based on the DTV signals; and

determine a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

80. The computer program product of claim 79, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

adjust the pseudo-ranges based on a difference between a transmitter clock at one of the DTV transmitters and a known time reference; and

determine the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

81. The computer program product of claim 79, wherein the known component is a scattered pilot carrier.

82. The computer program product of claim 79, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

determine an offset between a local time reference in the user terminal and a master time reference; and

determine the position of the user terminal based on the pseudo-ranges, the location of each of the DTV transmitters, and the offset.

83. The computer program product of claim 82, further comprising instructions operable to cause a programmable processor to:

determine a subsequent position of the user terminal using the offset.

84. The computer program product of claim 79, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

determine a general geographic area within which the user terminal is located; and

determine the position of the user terminal based on the pseudo-ranges and the general geographic area.

85. The computer program product of claim 84, wherein the general geographic area is a footprint of an additional transmitter communicably linked to the user terminal.

86. The computer program product of claim 79, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

determine a tropospheric propagation velocity in the vicinity of the user terminal;

adjust the value of each pseudo-range based on the tropospheric propagation velocity; and

determine the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.

87. The computer program product of claim 79, wherein instructions operable to cause a programmable processor to determine a position of the user terminal comprise instructions operable to cause a programmable processor to:

adjust each pseudo-range based on the terrain elevation in the vicinity of the user terminal; and

determine the position of the user terminal based on the adjusted pseudo-ranges and the location of each of the DTV transmitters.