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A mobile communications device uses a method for determining position that involves a positioning filter, such as a Kalman filter, which is initialized with measurements from reference stations such as satellite vehicles and/or base stations which may be acquired during different epochs. Accordingly

A mobile communications device uses a method for determining position that involves a positioning filter, such as a Kalman filter, which is initialized with measurements from reference stations such as satellite vehicles and/or base stations which may be acquired during different epochs. Accordingly, the positioning filter may be used for position estimation without the need to first acquire at least three different signals during the same measurement epoch.

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1. A method for estimating a position fix using a Kalman filter implemented in a mobile communications device comprising a satellite position system (SPS) receiver and a processor, the method comprising: starting a measurement session that uses the SPS receiver and the processor;acquiring a first ps

1. A method for estimating a position fix using a Kalman filter implemented in a mobile communications device comprising a satellite position system (SPS) receiver and a processor, the method comprising: starting a measurement session that uses the SPS receiver and the processor;acquiring a first pseudoranging measurement set, during a first measurement epoch, corresponding to respective ranges from a first subset of reference stations to the mobile communications device, said first measurement epoch including a start of the measurement session, said first subset being less than three reference stations;initializing the Kalman filter, using at least the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different reference stations during the same measurement epoch;acquiring a second pseudoranging measurement set, during a second measurement epoch, corresponding to respective ranges from a second subset of reference stations to the mobile communications device, during a second measurement epoch that is subsequent to said first measurement epoch, said second subset of reference stations including at least one reference station not included in said first subset of reference stations; andestimating a position fix of the mobile communications device, comprising updating the initialized Kalman filter using at least the second pseudoranging measurement set, prior to acquiring simultaneous pseudoranging measurements from at least three different reference stations during the same measurement epoch. 2. The method of claim 1, the first subset of reference stations and the second subset of reference stations not sharing a common satellite vehicle reference station. 3. The method of claim 1, the first subset of reference stations and the second subset of reference stations sharing at least one common satellite vehicle reference station. 4. The method of claim 1, further comprising: receiving at the mobile communications device position assistance information from a cellular communications network,said initializing the Kalman filter being configured to use at least a portion of the position assistance information in combination with the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different reference stations during the same measurement epoch, andthe estimating the position fix of the mobile communications device being configured to estimate the position as a three-dimensional position, updating the initialized Kalman filter. 5. The method of claim 4, the cellular communications network being configured to include a CDMA network. 6. The method of claim 4, the estimated initial three-dimensional position fix being configured to include a location value and an uncertainty value. 7. The method of claim 4, said initializing the Kalman filter comprising: seeding a portion of a state vector of the Kalman filter with at least a portion of the first pseudoranging measurement set and at least a portion of the received position assistance information. 8. The method of claim 4, said initializing the Kalman filter comprising: seeding a portion of a covariance matrix of the Kalman filter with at least a portion of the received position assistance information in combination with the first pseudoranging measurement set. 9. The method of claim 1, the first pseudoranging measurement set comprising a pseudoranging measurement that is related to a Global Positioning System. 10. The method of claim 1, further comprising: refining the estimated position fix of the mobile communications device, comprising subsequent updating the Kalman filter, with subsequent pseudoranging measurement sets acquired at the mobile communication device, corresponding to respective ranges from any of a plurality of reference stations during one or more measurement epochs subsequent to the second measurement epoch. 11. A method for estimating a position fix of a mobile communications device including a wireless receiver and a processor, the method comprising: starting a measurement session that uses the wireless receiver and the processor;acquiring a first pseudoranging measurement set during a first measurement epoch, corresponding to ranges from a first subset of pseudoranging sources to the mobile communications device, said first measurement epoch including a start of the measurement session, said first subset being less than three pseudoranging sources;initializing the Kalman filter implemented in the mobile communications device, using at least the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different pseudoranging sources during the same measurement epoch;acquiring a second pseudoranging measurement set during a second measurement epoch, corresponding to respective ranges from a second subset of pseudoranging sources to the mobile communications device, during a second measurement epoch that is subsequent to said first measurement epoch, and said second subset of pseudoranging sources comprising at least one pseudoranging source that is not in said first subset of pseudoranging sources; andestimating a position fix of the mobile communications device, comprising updating the initialized Kalman filter using at least the second pseudoranging measurement set, prior to acquiring simultaneous pseudoranging measurements from at least three different pseudoranging sources during the same measurement epoch. 12. The method of claim 11, the pseudoranging sources comprising terrestrial wireless network base stations. 13. The method of claim 11, the pseudoranging sources comprising a combination of terrestrial wireless network base stations and reference stations. 14. The method of claim 11, the pseudoranging sources comprising satellites of a satellite positioning system. 15. A mobile communications device comprising: a Kalman filter;a first receiver, configured to receive signals related to a satellite positioning system;a second receiver, configured to receive signals related to a communications network; anda processor, adapted to communicate with the first and second receiver, the processor being further adapted to: start a measurement session; acquire, using the first receiver, a first pseudoranging measurement set during a first measurement epoch, corresponding to respective ranges from a first subset of reference stations, of the satellite positioning system, to the mobile communications device, said first measurement epoch including a start of the measurement session;initialize the Kalman, using at least the first pseudoranging measurement set, prior to acquiring simultaneous measurements of signals from at least three different reference stations during the same measurement epoch;acquire, using the first receiver, a second pseudoranging measurement set during a second measurement epoch, corresponding to respective ranges from a second subset of reference stations, of the satellite positioning system, to the mobile communications device, said second measurement epoch being subsequent to said first measurement epoch, and said second subset of reference stations comprising at least one reference station that is not in said first subset of reference stations; andto estimate a position fix of the mobile communications device, comprising updating the initialized Kalman filter using at least the second pseudoranging measurement set, prior to acquiring simultaneous pseudoranging measurements from at least three different reference stations of the satellite positioning system during the same measurement epoch. 16. The device of claim 15, the first subset of reference stations and the second subset of reference stations not sharing a common satellite vehicle reference station. 17. The device of claim 15, the first subset of reference stations and the second subset of reference stations sharing at least one common satellite vehicle reference station. 18. The device of claim 15, the second receiver being further adapted to receive position assistance information from the communications network, said processor being further adapted to initialize the Kalman filter, using at least a portion of the position assistance information in combination with the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different reference stations during the same measurement epoch, andthe processor being further adapted to estimate the position fix as a three-dimensional position fix of the mobile communications device, updating the initialized Kalman filter. 19. The device of claim 18, the communications network being configured to include a CDMA network. 20. The device of claim 18, the estimated initial position fix being configured to include a location value and an uncertainty value. 21. The device of claim 18, the processor being further adapted to include, in operations to initialize the Kalman filter, operations to: seed a portion of a state vector of the Kalman filter and a portion of a covariance matrix of the Kalman filter with at least a portion of the received position assistance information. 22. The device of claim 15, the first pseudoranging measurement being configured in a relation to a Global Positioning System. 23. The device of claim 15, the processor being further adapted to: refine the estimated position fix of the mobile communications device, including to update the initialized with subsequent pseudoranging measurements acquired from any of a plurality of reference stations of the satellite positioning system during one or more measurement epochs subsequent to the second measurement epoch. 24. A method for estimating a position fix, using a Kalman filter implemented in a mobile communications device comprising a satellite positioning system (SPS) receiver and a processor, the method comprising: starting a measurement session, using the SPS receiver and the processor;acquiring a first pseudoranging measurement set, during a first measurement epoch, corresponding to respective ranges from a first subset of reference stations, said first measurement epoch including a start of the measurement session;initializing the Kalman filter, using at least the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different reference stations during the same measurement epoch;acquiring a second pseudoranging measurement set, corresponding to respective ranges from a second subset of reference stations to the mobile communications device, during a second measurement epoch that is subsequent to said first measurement epoch, said second subset of reference stations comprising at least one reference station that is not in said first subset of reference stations;using back propagation to determine time for the first subset of reference stations and the second subset of reference stations, based on SPS time acquired after acquiring the first pseudoranging measurement set and acquiring the second pseudoranging measurement set; andestimating a position fix of the mobile communications device, using determined time for the first subset of reference stations and the second subset of reference stations and comprising updating the initialized Kalman filter using at least the second pseudoranging measurement set, prior to acquiring simultaneous pseudoranging measurements from at least three different reference stations during the same measurement epoch. 25. A non-transitory computer readable medium embodying a program of instructions executable by one or more processors of a mobile communications device also comprising a Satellite Positioning System (SPS) receiver, to adapt said one or more processors to: start a measurement session that uses the SPS receiver and the processor;acquire, using the SPS receiver, a first pseudoranging measurement set during a first measurement epoch, corresponding to respective ranges from a first subset of reference stations to the mobile communications device, said first measurement epoch including a start of the measurement session;initialize the Kalman filter, using at least the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different reference stations during the same measurement epoch;acquire a second pseudoranging measurement set, corresponding to respective ranges from a second subset of reference stations to the mobile communications device, during a second measurement epoch that is subsequent to said first measurement epoch, said second subset of reference stations comprising at least one reference station that is not in said first subset of reference stations; andestimating a position fix of the mobile communications device, comprising updating the initialized Kalman filter, using at least the second pseudoranging measurement set, prior to acquiring simultaneous pseudoranging measurements from at least three different reference stations during the same measurement epoch. 26. The non-transitory computer readable medium of claim 25, further comprising program instructions executable by said one or more processors to use back propagation to determine time for the first subset of reference stations and the second subset of reference stations based on Satellite Positioning System (SPS) time acquired after the first pseudoranging measurement set and the second pseudoranging measurement set. 27. A mobile communications device comprising: a first receiver means for receiving signals related to a satellite positioning system;a second receiver means for receiving signals related to a communications network; anda processor means adapted to communicate with the first receiver means and the second receiver means, the processor means comprising a Kalman filter, and adapted to: start a measurement session, using at least the first receiver means;acquire, using at least the first receiver means, a first pseudoranging measurement set during a first measurement epoch, corresponding to respective ranges from a first subset of reference stations to the mobile communications device, said first measurement epoch including a start of the measurement session;initialize the Kalman filter, using at least the first pseudoranging measurement set, prior to acquiring simultaneous measurements at the mobile communications device of signals from at least three different reference stations during the same measurement epoch;acquire, using at least the first receiver means, a second pseudoranging measurement set during a second measurement epoch, corresponding to respective ranges from a second subset of reference stations of the satellite positioning system to the mobile communications device, said second measurement epoch being subsequent to said first measurement epoch, and said second subset of reference stations comprising at least one reference station that is not included in said first subset of reference stations; andestimate a position fix of the mobile communications device, comprising updating the initialized Kalman filter, using at least the second pseudoranging measurement set, prior to acquiring simultaneous pseudoranging measurements from at least three different reference stations during the same measurement epoch. 28. The method of claim 1, said first subset of reference stations and said second subset of reference stations being satellite vehicles. 29. The method of claim 1, further comprising: determining whether an uncertainty value associated with position fix meets an uncertainty requirement associated with an application executing on the mobile communications device; andproviding the position fix and the uncertainty value associated therewith to the application executing on the mobile communications device in response to the uncertainty value associated with the position fix meeting the uncertainty requirement associated with the application. 30. The method of claim 10, further comprising: determining that a first uncertainty value associated with the position fix does not meet an uncertainty requirement associated with an application executing on the mobile communications device;determining that a second uncertainty value associated with the refined position fix meets the uncertainty requirement associated with the application executing on the mobile communications device; andproviding the refined position fix and the second uncertainty value to the application executing on the mobile communications device.