System and method for rapid telepositioning

• US 6,560,536 B1
• Filed: 04/11/2001
• Issued: 05/06/2003
• Est. Priority Date: 07/12/1999
• Status: Expired due to Term

• Current Assignee: SkyBitz, Inc. (Ametek Incorporated)
• Original Assignee: Eagle Eye, Inc.
• Inventors: Sullivan, Mark C., Kilfeather, James B.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): To, Tuan C
• Application Number:
  US09/829,993
• Time in Patent Office: 755 Days
• Field of Search: 701/213, 701/214, 701/215, 701/207, 342/357, 342/357.09, 342/357.02, 342/357.01, 342/357.03, 342/357.05, 342/357.06, 342/357.12, 342/357.16, 342/33, 342/387, 379/59, 370/321, 455/440, 455/456, 455/12.1, 455/422, 375/96, 779/60
• US Class Current: 701/214
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A geographic tracking system with minimal power and size required at the mobile terminal collects observation data at the mobile terminal, forwards the data to a processor, which calculates the position. The mobile terminal needs only to gather a few milliseconds of observation data, and to relay this observation data to the processor. The range from the satellite (or other airborne transponder) to the terminal is determined using the known positions of an interrogating transmitter and a satellite, and a known terminal delay between the received signal and the transmission of the return signal, and the round trip time. An arc of locations is determined by computing an intersection of a sphere centered at the satellite having a radius given by the calculated range with a model of the Earth'"'"'s surface. Alternatively, candidate locations that are consistent with the carrier signal received from GPS satellites can be used. In either case, the candidate points are considered and refined using code phase measurements from a set of GPS satellites. The candidate point having the lowest residuals or expected to measured code phases is chosen as the location of the mobile terminal. The measurements can be refined to account for various sources of error including measurement bias, relative motion and timing errors.

Claims

1. A system for providing location information, comprising:

a mobile terminal that receives a global positioning system (GPS) signal having a carrier frequency and code phase information from a plurality of global positioning satellites, and measures the carrier frequency and code phase for each of the GPS signals from the plurality of GPS satellites;

a SOC to which the mobile terminal sends a message containing the received carrier frequency and code phase measurements for each of the received signals, the SOC using the signal characteristics to determine a set of coarse locations in a general region in which the mobile terminal is located, and the code phase measurements to refine the coarse locations and determine a final position of the mobile terminal.

2. The system recited in claim 1, wherein the message further comprises a time that the carrier frequency measurement for each of the received GPS signals in addition to the carrier frequency and code phase measurements.

3. The system recited in claim 1, wherein the message is transmitted over a cellular telephone network.

4. The system recited in claim 1, wherein the message is transmitted using a satellite.

5. The system recited in claim 1, wherein the SOC further comprises means for removing bias due to local oscillator inaccuracies from the carrier estimates.

6. The system recited in claim 1, wherein the SOC further comprises means for accounting for time measurement errors in the time that the carrier frequency measurements were made.

7. The system recited in claim 1, wherein the SOC further comprises means for accounting for motion of the mobile terminal relative to the GPS satellites.

8. A method for determining a location of a mobile terminal, comprising the steps of:

(a) collecting GPS signal data from each of a plurality of GPS satellites;

(b) transmitting a message containing the GPS signal data to a service operation center;

(c) determining an observed carrier frequency for each of the GPS satellites from the GPS signal data collected from each of the GPS satellites and a time the mobile terminal received the GPS signal data from which each observed carrier frequency is determined;

(d) determining a general region in which the mobile terminal is located; and

(e) determining at least one candidate location in the general region that is consistent with the observed carrier frequencies.

9. The method recited in claim 8, wherein step (e) comprises the steps of:

(e.1) selecting an initial candidate location; and

(e.2) searching the general region for a location consistent with the observed carrier frequencies using the initial candidate location.

10. The method recited in claim 9, further comprising the step of repeating steps (e.1) and (e.2) at least one additional time using a different initial candidate point to being each repetition.

11. The method recited in claim 9, further comprising the step of using a Mead simplex algorithm to search the general region.

12. The method recited in claim 9, further comprising the steps of:

(f) determining a code phase for each of the GPS satellites associate with each of the at least one candidate locations; and

(g) refining the at least one candidate locations using the code phases.

13. The method recited in claim 12, further comprising the steps of:

(h) determining residuals for each of the candidate locations using the code phases; and

(i) selecting the candidate location having the lowest residuals as the location of the mobile terminal.

14. A system for determining a location of a mobile terminal, comprising:

means for collecting a GPS signal from each of a plurality of GPS satellites;

means for measuring a first signal characteristic of each GPS signal;

means for measuring a second signal characteristic of each GPS signal; and

means for sending the measured first and second signal characteristics of each GPS signal to a service operation center;

means for sending a time the first and second signal characteristics of each GPS signal are measured to the service operation center;

means for determining one or more candidate locations using the first signal characteristic; and

means for determining the location of the mobile terminal using the second signal characteristic and the one or more candidate locations.

15. The system recited in claim 14, wherein the means for measuring a first signal characteristic comprises means for determining carrier frequency for each GPS signal.

16. The system recited in claim 14, wherein the means for measuring a second signal characteristic comprises means for determining code phase for each GPS signal.

17. The system recited in claim 14, wherein the means for determining one or more candidate locations, comprises:

(a) means for selecting a general region containing the location of the mobile terminal;

(b) means for selecting a starting location in the general region;

(c) means for determining an expected first signal characteristic for each of the GPS satellites at the starting location;

(d) means for comparing the expected first characteristic signal with the measure first characteristic for each of the GPS signals; and

(e) means for applying a function minimization algorithm to determine a candidate location in the general region corresponding the starting location.

18. The system recited in claim 17, further comprising:

means for selecting a second starting point in the general region; and

means for applying means (a)-(c) to the second starting point to determine a second candidate location in the general region.

19. The system recited in claim 17, wherein the measured and expected first characteristics are carrier frequencies.

20. A method for determining a location of a mobile terminal, comprising the steps of:

(a) collecting a GPS signal from each of a plurality of GPS satellites;

(b) measuring a first signal characteristic of each GPS signal;

(c) measuring a second signal characteristic of each GPS signal; and

(d) sending the measured first and second signal characteristics of each GPS signal to a service operation center;

(e) sending a time the first and second signal characteristics of each GPS signal are measured to the service operation center;

(f) determining one or more candidate locations using the first signal characteristic; and

(g) determining the location of the mobile terminal using the second signal characteristic and the one or more candidate locations.

21. The method recited in claim 20, wherein the step of measuring a first signal characteristic comprises the step of determining carrier frequency for each GPS signal.

22. The method recited in claim 20, wherein the step of measuring a second signal characteristic comprises the step of determining code phase for each GPS signal.

23. The system recited in claim 20, wherein the step of determining one or more candidate locations, comprises the steps of:

(f.1) selecting a general region containing the location of the mobile terminal;

(f.2) selecting a starting location in the general region;

(f.3) determining an expected first signal characteristic for each of the GPS satellites at the starting location;

(f.4) means for comparing the expected first characteristic signal with the measure first characteristic for each of the GPS signals; and

(f.5) means for applying a function minimization algorithm to determine a candidate location in the general region corresponding the starting location.

24. The system recited in claim 23, further comprising the steps of:

selecting a second starting point in the general region; and

applying means (a)-(c) to the second starting point to determine a second candidate location in the general region.

25. The system recited in claim 23, wherein the measured and expected first characteristics are carrier frequencies.