Bootstrapped location determination

• US 6,239,721 B1
• Filed: 10/26/1998
• Issued: 05/29/2001
• Est. Priority Date: 10/26/1998
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Smith, Derek Steve
• Primary Examiner(s): ZIMMERMAN, BRIAN A
• Application Number:
  US09/178,048
• Time in Patent Office: 946 Days
• Field of Search: 342/357, 342/357.14, 342/357.06, 342/457, 340/826.49, 340/988
• US Class Current: 340/8.1
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type

Abstract

A system for determining the location of a moving signal-receiving station, when the primary location determination (LD) signals become unavailable because the antenna is adjacent to or within a signal-interfering structure, such as an urban canyon, a natural canyon, a forest or the like. Before the primary LD signals become unavailable, secondary LD signals are received at spaced apart locations and used to estimate the secondary LD signal source locations (preferably fixed). After the primary LD signals become unavailable, secondary LD signals, now with known source locations, are received and used, either alone or in combination with the remaining primary LD signals, if any, to determine the present location of the moving station. The primary LD signal sources can be GPS or GLONASS or LEO or other satellite-based sources. The secondary LD signal sources can be pseudolites or Loran signal towers or other ground-based sources.

Claims

1. A method for determining the location of a moving signal receiver, the method comprising the steps of:

receiving primary location determination (LD) signals from two or more primary LD signal sources, whose locations are known, at a primary LD signal antenna and associated signal receiver;

when sufficient primary LD signals are available, estimating the present location of the primary antenna;

receiving secondary location determination (LD) signals from one or more secondary LD signal sources, whose locations are not necessarily known, at a secondary LD signal antenna at each of two or more spaced apart locations and estimating the location of each of the at least one secondary LD signal sources, using knowledge of the present location of the primary antenna; and

when sufficient primary LD signals are unavailable to determine location of the primary antenna, analyzing the primary LD signals received and the secondary LD signals received and estimating the present location of at least one of the primary antenna and the secondary antenna.

2. The method of claim 1, further comprising the step of providing each of said at least one secondary LD signals with a selected indicium that allows each of said at least one secondary LD signals to be identified.

3. The method of claim 2, further comprising the step of selecting said indicium from the group consisting of an FDMA indicium and a CDMA indicium.

4. The method of claim 1, further comprising the step of providing time synchronization for each of said secondary LD signal sources.

5. The method of claim 1, further comprising the step of providing and using said secondary LD signals from at least two of said secondary LD signal sources to estimate said present location of said secondary antenna.

6. The method of claim 1, further comprising the step of providing at least one of said primary LD signals from one or more satellite that are part of a satellite-based location determination system drawn from a group consisting of a Global Positioning System, a Global Orbiting Navigational Satellite System and a Low Earth Orbit system.

7. A system for determining the location of a moving signal receiver, the system comprising:

a primary location determination (LD) signal antenna and receiver that receives primary LD signals from two or more primary LD signal sources, whose locations are known;

a secondary LD signal antenna and receiver, positioned adjacent to the primary antenna, that receives secondary location determination (LD) signals from one or more secondary LD signal sources, whose locations are not necessarily known, at each of two or more spaced apart secondary antenna locations and estimates the distance between each secondary LD signal source location and the present location of the primary antenna; and

a computer that is programmed;

to estimate the location of each of the at least one secondary LD signal sources, using knowledge of the present location of the primary antenna;

when sufficient primary LD signals are available, to estimate the present location of the primary antenna; and

when sufficient primary LD signals are unavailable to determine location of the primary antenna, to analyze the primary LD signals and the secondary LD signals received and to estimate the present location of at least one of the primary antenna and the secondary antenna.

8. The system of claim 7, wherein each of said at least one secondary LD signals is provided with a selected indicium that allows each of said at least one secondary LD signals to be identified.

9. The system of claim 8, wherein said indicium is selected from the group consisting of an FDMA indicium and a CDMA indicium.

10. The system of claim 7, wherein said computer is further programmed to provide time synchronization for signals received at said secondary antenna.

11. The system of claim 7, wherein said secondary LD signals from at least two of said secondary LD signal sources are used to estimate said present location of said secondary antenna.

12. The system of claim 7, wherein said primary LD signals are provided by one or more satellites that are part of a satellite-based location determination system drawn from a group consisting of a Global Positioning System, a Global Orbiting Navigational Satellite System and a Low Earth Orbit system.