System and method for fast acquisition reporting using communication satellite range measurement

• US 20040143392A1
• Filed: 01/12/2004
• Published: 07/22/2004
• Est. Priority Date: 07/12/1999
• Status: Abandoned Application

• Current Assignee: SkyBitz, Inc. (Ametek Incorporated)
• Original Assignee: SkyBitz, Inc. (Ametek Incorporated)
• Inventors: Sullivan, Mark C., Kilfeather, James B.
• Application Number:
  US10/754,492
• Publication Number:
  US 20040143392A1
• Time in Patent Office: Days
• US Class Current: 701/213
• 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 5/14 Determining absolute distances from a plurality of spaced points of known location

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. 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 method for determining a location of a remote terminal, comprising:

receiving a communication from a remote terminal via a communications satellite, said communication in response to an interrogation signal and including a measured characteristic of a plurality of signals broadcast by a respective plurality of GPS satellites;

determining a range measurement between the communications satellite and the remote terminal using said received communication;

determining an arc of possible locations of the remote terminal using said determined range measurement; and

identifying a final location of the remote terminal using said measured characteristics of said plurality of signal broadcast by said respective plurality of GPS satellites.

2. The method of claim 1, wherein said range measurement determination is based on a removal of known delays from a propagation time measurement.

3. The method of claim 1, wherein said determination of said arc of possible locations is based on a model of the surface of the Earth.

4. The method of claim 1, wherein said measured characteristic is a code phase of arrival measurement.

5. A method in a remote terminal that enables position determination, comprising:

receiving an interrogation signal from a communications satellite;

measuring in response to said interrogation signal at least one characteristic of a plurality of signals broadcast by a respective plurality of GPS satellites;

transmitting a response to a centralized location via said communications satellite, said response including said measured characteristic of said plurality of signals broadcast by said respective plurality of GPS satellites, wherein said measured characteristic is used by said centralized location to identify a final location of the remote terminal from an arc of possible locations defined by a range measurement between the communications satellite and the remote terminal.

6. The method of claim 5, wherein said range measurement is determined by removing known delays from a propagation time measurement between said centralized location and the remote terminal.

7. The method of claim 5, wherein said measured characteristic is a code phase of arrival measurement.

8. A computer-readable medium that stores a program for controlling a computer device to perform a method for determining a location of a remote terminal, the method comprising:

receiving a communication from a remote terminal via a communications satellite, said communication in response to an interrogation signal and including a measured characteristic of a plurality of signals broadcast by a respective plurality of GPS satellites;

determining a range measurement between the communications satellite and the remote terminal using said received communication;

determining an arc of possible locations of the remote terminal using said determined range measurement; and

identifying a final location of the remote terminal using said measured characteristics of said plurality of signal broadcast by said respective plurality of GPS satellites.