Method and system for processing positioning signals based on predetermined message data segment
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.
1. A method for synchronizing a time setting of a clock in a receiver with a Global Positioning System (GPS) time in a clock of each of a plurality of satellites, comprising:
recording a predetermined segment of a signal received from each of at least four satellites;
establishing a time of arrival of a predetermined message data sequence in each received signal;
determining a time difference of arrival for at least three pairs of satellites;
computing a location of the receiver from the time difference of arrival;
locating a HOW word in the received signal preceding the predetermined message data segment;
extracting a GPS time from the HOW word;
identifying a GPS time of transmission from each satellite of the predetermined message data sequence from the extracted GPS time and a separation between the HOW word and the predetermined message data segment;
calculating a propagation time of the signal from each satellite to the receiver based on the location of the satellites and the location coordinates of the receiver;
obtaining GPS time of receipt at the receiver of the predetermined message data sequence from the propagation time and the GPS time of transmission;
formulating a receiver clock error from the GPS time of receipt and the time of arrival for a given satellite.
2. The method of claim 1 , wherein the predetermined segment is an amount of signal received in a recording session of up to six seconds.
3. The method of claim 1 , wherein formulating the receiver clock error includes obtaining a best estimate of the receiver clock error using all of the satellites.
4. The method of claim 1 , further comprising:
resetting the receiver clock by an amount of the receiver clock error.
5. The method of claim 4 , further comprising:
determining whether the receiver clock was reset by more than a desired threshold value;
repeating the recording, establishing, determining, computing, locating, extracting, identifying, calculating, obtaining and formulating steps in response to the reset being more than the desired threshold value.
6. A system for synchronizing a time setting of a clock in a receiver with a Global Positioning System (GPS) time in a clock of each of a plurality of satellites, comprising:
means for recording a predetermined segment of a signal received from each of at least four satellites;
means for establishing a time of arrival of a predetermined message data sequence in each received signal;
means for determining a time difference of arrival for at least three pairs of satellites;
means for computing a location of the receiver from the time difference of arrival;
means for locating a HOW word in the received signal preceding the predetermined message data segment;
means for extracting a GPS time from the HOW word;
means for identifying a GPS time of transmission from each satellite of the predetermined message data sequence from the extracted GPS time and a separation between the HOW word and the predetermined message data segment;
means for calculating a propagation time of the signal from each satellite to the receiver based on the location of the satellites and the location coordinates of the receiver;
means for obtaining GPS time of receipt at the receiver of the predetermined message data sequence from the propagation time and the GPS time of transmission;
means for formulating a receiver clock error from the GPS time of receipt and the time of arrival for a given satellite.
7. The system of claim 6 , wherein the predetermined segment is an amount of signal received in a recording session of up to six seconds.
8. The system of claim 6 , wherein formulating the receiver clock error includes making a best estimate of the receiver clock error using all of the satellites.
9. The system of claim 6 , further comprising:
resetting the receiver clock by an amount of the receiver clock error.
10. The system of claim 9 , further comprising:
determining whether the receiver clock was reset by more than a desired threshold value;
repeating the recording, establishing, determining, computing, locating, extracting, identifying, calculating, obtaining and formulating steps in response to the reset being more than the desired threshold value.