Method and system for processing positioning signals based on predetermined message data segment

Abstract

A method and system for determining a geolocation of an object includes collecting a positioning signal including a predetermined message data segment. A time of arrival of the predetermined message data segment may be determined in the positioning signal. Information based on the time of arrival may be provided for determination of a geolocation of an object. The time of arrival of the predetermined message data segment may be determined based on a time search for the predetermined message data segment in the positioning signal.

What is claimed is: 
     
         1 . A method for synchronizing a time setting of a clock in a receiver with a GPS time in a clock of a plurality of satellites, comprising:
 receiving a signal from each of the plurality of satellites, each signal including a predetermined message data sequence;   identifying a time of receipt and a time of transmission of each predetermined message data sequence;   determining a geolocation of the receiver from each time of receipt;   computing an error in the receiver clock using the geolocation of the receiver, the time of receipt, and the time of transmission of the predetermined message data sequence.   
     
     
         2 . The method of  claim 1 , wherein the error is a difference between a clock time in a satellite and a clock time in the receiver determined at a moment of receipt from that satellite of the predetermined message data sequence. 
     
     
         3 . The method of  claim 1 , further comprising:
 resetting the receiver clock by an amount of the error.   
     
     
         4 . The method of  claim 1 , further comprising:
 detecting whether an amount of the error is greater than a desired threshold;   repeating the determining, receiving, and computing steps in response to the error being greater than the desired threshold.   
     
     
         5 . The method of  claim 1 , wherein the geolocation includes a built-in error attributable to the error in the receiver clock and a consequential error in locations of the satellites. 
     
     
         6 . The method of  claim 5 , wherein the locations of the satellites are derived from ephemeris or almanac information used in computing the receiver geolocation. 
     
     
         7 . The method of  claim 6 , further comprising:
 determining a signal propagation time from each satellite to the receiver from the locations of the satellites and the geolocation of the receiver.   
     
     
         8 . The method of  claim 1 , wherein the time of transmission is identified by identifying a HOW word from the signal and extracting a time from the HOW word. 
     
     
         9 . The method of  claim 1 , wherein the error is computed using a given one of the satellites. 
     
     
         10 . The method of  claim 1 , wherein the error is computed by analyzing results from all of the satellites and performing statistical techniques to determine a best estimate of the error.