Method and apparatus for determining global position using almanac information
First Claim
Patent Images
1. A method for determining a location of a mobile station, comprising:
- the mobile station computing a tentative satellite visibility list using stored satellite almanac information, wherein the stored satellite almanac information includes a plurality of sub-almanac identifications;
the mobile station transmitting the tentative satellite visibility list and the sub-almanac identifications to a location server;
the mobile station transmitting a computed maximum error parameter to the location server;
the location server calculating at least one actual error between at least one satellite position calculated using the sub-almanac information indicated by the sub-almanac identifications, and at least one satellite position calculated using current ephemeris data; and
the location server transmitting replacement sub-almanac information to the mobile station if an actual error exceeds the maximum error parameter.
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Accused Products
Abstract
In a satellite global positioning system, satellite acquisition and location assistance is based upon shared information between a GPS receiver and a remote server. Satellite position is predicted by satellite almanac data.
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Citations
17 Claims
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1. A method for determining a location of a mobile station, comprising:
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the mobile station computing a tentative satellite visibility list using stored satellite almanac information, wherein the stored satellite almanac information includes a plurality of sub-almanac identifications;
the mobile station transmitting the tentative satellite visibility list and the sub-almanac identifications to a location server;
the mobile station transmitting a computed maximum error parameter to the location server;
the location server calculating at least one actual error between at least one satellite position calculated using the sub-almanac information indicated by the sub-almanac identifications, and at least one satellite position calculated using current ephemeris data; and
the location server transmitting replacement sub-almanac information to the mobile station if an actual error exceeds the maximum error parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
the mobile station computing coarse position information using the stored almanac information and any replacement sub-almanac information received; and
the mobile station transmitting the coarse position information to the location server.
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4. The method of claim 3, further comprising the mobile station transmitting a position difference to the location server, wherein the position difference comprises a difference between a position calculated by the mobile station and the reference position.
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5. The method of claim 3, further comprising the location server calculating pseudorange corrections to the coarse information using ephemeris data.
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6. The method of claim 5, further comprising:
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the location server calculating position corrections and time corrections using the pseudorange corrections; and
the location server using the position corrections and time corrections to calculate a corrected coarse position.
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7. The method of claim 6, further comprising the location server sending the corrected coarse position to the mobile station.
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8. The method of claim 1, further comprising,
the location server computing a true satellite visibility list using complete almanac information; - and
if the true satellite visibility list includes a sub-almanac not included in the tentative satellite visibility list, transmitting the sub-almanac to the mobile station.
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9. A system for determining a position of an object, comprising:
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a mobile station comprising a global positioning system (“
GPS”
) receiver, wherein the mobile station is configured to compute an approximate GPS satellite visibility list from stored sub-almanacs; and
a position determining entity (“
PDE”
) communicatively coupled to the mobile station, wherein the PDE is configured to receive almanac and ephemeris data, the PDE comprising,a memory device for storing almanac data and ephemeris data; and
a central processing unit configured to, calculate an error between a position calculated using the ephemeris data and a position calculated using sub-almanac data received from the mobile station; and
transmit a replacement sub-almanac to the mobile station if an error calculated using a sub-almanac is greater than a pre-determined value;
wherein the mobile station uses the stored sub-almanacs, any replacement sub-almanacs received, and GPS measurements to compute a coarse position. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. An electromagnetic medium containing instructions which, when read by a processor, cause the processor to:
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calculate a position using ephemeris data;
calculate a position using sub-almanac data received from a mobile unit;
calculate an error between the positions calculated; and
if the error exceeds a pre-determined error value, sending a replacement sub-almanac to the mobile station for each sub-almanac associated with the error, wherein the replacement sub-almanac is stored with other sub-almanacs as a set of validated sub-almanacs used by the mobile station to calculate a coarse position. - View Dependent Claims (17)
receive the coarse position from the mobile station;
compute a pseudorange correction between a position calculated using the validated sub-almanacs and ephemeris data, including consideration of differential GPS corrections;
compute position and time corrections from the pseudorange corrections; and
include the position and time corrections in the coarse position.
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Specification