Method and Apparatus for Processing of Satellite Signals Without Time of Day Information
Method and apparatus for locating position of a satellite signal receiver is described. In one example, pseudoranges are obtained that estimate the range of a satellite signal receiver to a plurality of satellites. An absolute time and a position are computed using the pseudoranges at a first time. The absolute time is then used to compute another position at a subsequent time. In another example, a plurality of states associated with a satellite signal receiver are estimated, where the plurality of states includes a time tag error state. A dynamic model is then formed relating the plurality of states, the dynamic model operative to compute position of the satellite signal receiver.
1 . A method of locating position of a satellite signal receiver, comprising:
obtaining pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites;
computing an absolute time and a position using the pseudoranges at a first time;
using the absolute time to compute another position at a subsequent time.
2 . The method of claim 1 , wherein the computing comprises:
obtaining a-priori estimates of time and position; and
calculating the position and the absolute time of reception using a mathematical model that updates the a-priori estimates of time and position.
3 . The method of claim 1 , wherein the absolute time is used to compute the other position in response to the absolute time being computed to a predefined accuracy.
4 . The method of claim 3 , further comprising: deriving the predefined accuracy from at least one of the number of the pseudoranges obtained, a dilution or precision value related to the plurality of satellite signals, signal-to-noise ratios of the plurality of satellite signals, and a-posteriori pseudorange residuals.
5 . The method of claim 1 , further comprising:
computing a plurality of time tag errors using the pseudoranges at a respective plurality of times between the first time and the subsequent time; and
averaging the plurality of time tag errors to produce the absolute time.
6 . The method of claim 1 , wherein the other position is computed using a standard global positioning system calculation, and wherein the absolute time is used as a known value in the standard global positioning system calculation.
7 . The method of claim 1 , wherein the other position is computed using a mathematical model that updates a-priori estimates of time and position, and wherein the absolute time is used as an additional measurement in the mathematical model.
8 . The method of claim 1 , further comprising: sending the pseudoranges to a server using a wireless communication system, wherein the absolute time, the position, and the other position are computed using the server.
9 . The method of claim 1 , wherein the absolute time, the position, and the other position are computed within the satellite signal receiver.
10 . A system for computing position of a satellite signal receiver, comprising:
a mobile device comprising a satellite signal receiver and a wireless transceiver;
a server being in wireless communication with the mobile device, where the satellite signal receiver provides pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites, and the wireless transceiver transmits the pseudoranges to the server, and where the server computes an absolute time and a position of the satellite signal receiver using the pseudoranges at a first time, and uses the absolute time to compute another position of the satellite signal receiver at a subsequent time.
11 . A system, comprising:
a mobile device comprising a satellite signal receiver and a wireless transceiver;
a server being in wireless communication with the mobile device, where the satellite signal receiver provides pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites, and the wireless transceiver transmits the pseudoranges to the server, and where the server includes a sequential estimator having a plurality of states associated with a satellite signal receiver, the plurality of states including a time tag error state.
12 . The system of claim 11 , wherein the sequential estimator is a Kalman filter.
13 . A mobile device, comprising:
a satellite signal receiver for providing pseudoranges that estimate the range of the mobile device to a plurality of satellites; and
a sequential estimator having a plurality of states associated with the satellite signal receiver, the plurality of states including a time tag error state.
14 . The mobile device of claim 13 , wherein the sequential estimator is a Kalman filter.
15 . A method for calculating an absolute position of a GPS receiver and an absolute time of reception of satellite signals comprising:
providing pseudoranges that estimate the range of the GPS receiver to a plurality of GPS satellites,
wherein each pseudorange is composed of a measured submillisecond component and a calculated integer millisecond component, and wherein each pseudorange has a consistent common mode error;
providing an estimate of an absolute time of reception of a plurality of satellite signals;
providing an estimate of a position of the GPS receiver;
providing satellite ephemeris data;
computing absolute position and absolute time using said pseudoranges by updating said estimate of an absolute time and the estimate of position of the GPS receiver.