Method and apparatus for processing of satellite signals without time of day information
First Claim
1. A method for calculating position of a satellite signal receiver, comprising:
- providing pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites;
providing an estimate of a position of the satellite signal receiver;
providing an estimate of time;
relating the pseudoranges, the position estimate, and the time estimate to a plurality of position and time variables; and
computing at least one of absolute position and absolute time by updating only a subset of the position and time variables.
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Accused Products
Abstract
A method and apparatus for computing GPS receiver position without using absolute time information transmitted by the satellite or by an alternative source of timing available at the GPS receiver. The GPS receiver is contained in an integrated receiver that also includes a wireless communication transceiver, but does not have access to an accurate source of absolute time information. The wireless transceiver communicates through a wireless network to a server. The GPS receiver measures satellite pseudoranges and uses the wireless communication transceiver to send the pseudoranges to the server. The server fits the pseudoranges to a mathematical model in which the GPS receiver position and the absolute time are unknown parameters. The server then computes a position and absolute time that best fit the model, thus yielding the correct position for the GPS receiver, and the absolute time at which the pseudorange measurements were made.
177 Citations
25 Claims
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1. A method for calculating position of a satellite signal receiver, comprising:
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providing pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites;
providing an estimate of a position of the satellite signal receiver;
providing an estimate of time;
relating the pseudoranges, the position estimate, and the time estimate to a plurality of position and time variables; and
computing at least one of absolute position and absolute time by updating only a subset of the position and time variables. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
forming a-priori pseudorange-residuals;
forming a mathematical model relating the a-priori pseudorange-residuals to the subset of position and time variables; and
computing updates of the subset of estimated position and time variables that fit the mathematical model.
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8. The method of claim 7, wherein the a-priori pseudorange-residuals are a difference between expected ranges from the plurality of satellites to the position estimate, and the pseudoranges.
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9. The method of claim 7, wherein the expected ranges are computed at a time given by the time-estimate.
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10. The method of claim 7, wherein said mathematical model is a linearization of a Taylor series of a non-linear mathematical model.
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11. The method of claim 10, wherein said linearization is of the form:
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12. The method of claim 11, wherein one or more of the updates x, y, z, tc, and ts is assumed known and set equal to an assumed value in the mathematical model, so that the remaining updates may be computed.
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13. The method of claim 11, wherein one or more of the updates x, y, z, tc, and ts is assumed known, and added to the model as a pseudo-measurement so that the remaining updates may be computed.
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14. The method of claim 7, wherein other measurements or constraints are used in the mathematical model.
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15. The method of claim 7, wherein the position estimate is obtained from a location of a radio tower used to communicate with a mobile device containing the satellite signal receiver.
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16. The method of claim 7, wherein the time-estimate is obtained from a real time clock in a server, the server being located remotely from the satellite signal receiver.
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17. A method for calculating position of a satellite signal receiver comprising:
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providing pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites;
providing an estimate of a position of the satellite signal receiver;
computing an absolute position of the satellite signal receiver by updating the position estimate using a model relating the pseudoranges and the position estimate, the model being independent of absolute time. - View Dependent Claims (18, 19, 20, 21, 22)
forming a-priori pseudorange-residuals;
forming a mathematical model relating the a-priori pseudorange-residuals to the updates of the position estimate; and
computing updates of the position estimate that fit the mathematical model.
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20. The method of claim 19, wherein the a-priori pseudorange-residuals are a difference between expected ranges from the plurality of satellites to the position estimate, and the pseudoranges.
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21. The method of claim 19, wherein said mathematical model is a linearization of a Taylor series of a non-linear mathematical model.
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22. The method of claim 21, wherein said linearization is of the form:
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23. A system for computing position of a satellite signal receiver comprising:
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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 computes 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;
where the server relates the pseudoranges, a position estimate, and a time estimate to position and time variables and computes at least one of absolute position and absolute time for the satellite signal receiver by updating only a subset of position and time variables. - View Dependent Claims (24, 25)
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Specification