Location-determination method and apparatus
First Claim
1. A global positioning system, comprising:
- a) using a global positioning system (“
GPS”
) receiver to receive a GPS signal;
b) computing a pseudorange for a GPS satellite without performing signal tracking on the received GPS signal; and
c) using the computed pseudorange in a triangulation method that resolves an uncertainty in the last code segment transmitted by the satellite at the time the GPS signal is received to identify an estimated location of the GPS receiver.
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Abstract
Some embodiments of the invention provide a location-determination system that includes several transmitters and at least one receiver. Each transmitter transmits a signal that includes a unique periodically-repeating component, and the receiver receives a reference signal. Based on the received reference signal, the location-determination system identifies an estimated location of the receiver as follows. For each transmitter in a set of transmitters, the system computes a phase offset between the received reference signal and a replica of the transmitter'"'"'s periodically-repeating component. The system also identifies an approximate location of the receiver and an approximate receive time for the received signal. The system then uses the identified approximate location and time, and the computed phase offsets, to compute pseudoranges for the set of transmitters. Finally, the system identifies the estimated location of the receiver by using the computed pseudoranges.
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Citations
28 Claims
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1. A global positioning system, comprising:
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a) using a global positioning system (“
GPS”
) receiver to receive a GPS signal;
b) computing a pseudorange for a GPS satellite without performing signal tracking on the received GPS signal; and
c) using the computed pseudorange in a triangulation method that resolves an uncertainty in the last code segment transmitted by the satellite at the time the GPS signal is received to identify an estimated location of the GPS receiver. - View Dependent Claims (2, 26)
a) computing pseudoranges for at least two other GPS satellites without performing signal tracking on the received GPS signal; and
b) using the computed pseudoranges to perform triangulation to identify the estimated location of the GPS receiver.
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26. The global positioning system as in claim 1, wherein the uncertainty relates to the position in the PRN code of the chip being transmitted by the satellite at the time the GPS receiver receives its first sample of the PRN code.
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3. A method of computing a pseudorange for a GPS receiver and a GPS satellite, wherein the GPS receiver receives a GPS signal and the GPS satellite repeatedly transmits a code, the method comprising
a) identifying a phase offset between the received GPS signal and a replica of the satellite'"'"'s code, wherein the phase offset corresponds to a particular segment of the code; -
b) identifying an approximate GPS-receiver location;
c) identifying an approximate time for the received GPS signal;
d) computing the pseudorange for the GPS satellite based on the computed phase offset, the approximate GPS-receiver location, and the approximate time. - View Dependent Claims (4, 5, 6, 7, 8)
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9. A method of computing a pseudorange for a receiver and a transmitter, wherein the receiver receives a reference signal starting at a particular time and the transmitter transmits a signal with a periodically-repeating component, the method comprising
a) identifying a phase offset between the received reference signal and a replica of the transmitter signal'"'"'s periodically-repeating component, wherein the phase offset corresponds to a particular segment of the periodically-repeating component; -
b) computing the length of the particular segment;
c) computing the length of complete periodically-repeating components that the particular satellite has transmitted by the particular time after transmitting the particular segment;
d) calculating the pseudorange based on the computed lengths. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
a) calculating the number of complete periodically-repeating components that the particular satellite transmitted after the particular segment by the particular time; and
b) multiplying the calculated number by the length of the complete periodically-repeating component.
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13. The method of claim 9, wherein the transmitter is part of a GPS satellite and the receiver is a GPS receiver.
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14. The method of claim 13, wherein the satellite includes a clock and the clock differs from GPS clock by some error amount, the method further comprising:
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a) identifying the satellite'"'"'s clock error amount;
b) generating an error-correction factor;
c) taking the error-correction factor into account in calculating the pseudorange.
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15. The method of claim 14,
a) wherein generating an error-correction factor comprises multiplying the error amount by the speed of light; b) wherein taking the error-correction factor into account comprises adding the error-correction factor to the calculated pseudorange.
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16. The method of claim 13, wherein calculating the pseudorange further comprises:
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a) calculating an atmospheric-delay-correction factor for the satellite;
b) taking the correction factor into account in calculating the pseudorange.
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17. The method of claim 16, wherein taking the correction factor into account comprises adding the correction factor to the calculated pseudorange.
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18. For a global positioning system (“
- GPS”
) that includes a plurality of GPS satellites and a GPS-receiver, a method of identifying an estimated location of a GPS receiver, wherein each particular GPS satellite transmits a signal that includes a periodically-repeating code unique to the particular GPS satellite, wherein the GPS receiver receives a signal starting at a particular time, the method comprisinga) for each particular GPS satellite in a set of the GPS satellites, 1) determining a phase offset between the received signal and a replica of the satellite'"'"'s code, wherein the phase offset corresponds to a particular segment of the particular satellite'"'"'s code;
2) computing the length of the code segment;
3) computing the length of complete codes that the particular satellite transmitted after the code segment by the particular time; and
4) calculating a pseudorange for the particular satellite based on the computed lengths; and
b) identifying the estimated location of the receiver by using the computed pseudoranges. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
a) calculating the number of complete codes that the particular satellite transmitted after the code segment by the particular time; and
b) multiplying the calculated number of complete codes by the length of the satellite'"'"'s code.
- GPS”
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22. The method of claim 18, wherein each satellite includes a clock and the clock differs from GPS clock by some error amount, the method further comprising:
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for each particular satellite, a) identifying the particular satellite'"'"'s clock error amount;
b) generating an error-correction factor;
c) taking the error-correction factor into account in calculating the pseudorange for the particular satellite.
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23. The method of claim 22,
a) wherein generating an error-correction factor comprises multiplying the error amount by the speed of light; b) wherein taking the error-correction factor into account comprises adding the error-correction factor to the calculated pseudorange for the particular satellite.
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24. The method of claim 18, wherein calculating the pseudorange for each particular satellite further comprises:
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a) calculating an atmospheric-delay-correction factor for the particular satellite;
b) taking the correction factor into account in calculating the pseudorange for the particular satellite.
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25. The method of claim 24, wherein taking the correction factor into account comprises adding the correction factor to the calculated pseudorange for the particular satellite.
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27. A method for determining a location of a receiver, including altitude information, the method comprising the steps of:
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a) receiving a signal comprising a plurality of periodic location-determining signals from a plurality of signal sources;
b) providing timing information to said receiver that is accurate to within a predetermined time interval of less than one half of a period of one of said periodic location determining signals;
c) determining an approximate receiver location to within a predetermined spatial distance that is less than one half of said period multiplied by the speed of light;
d) using said timing information, said approximate receiver location and said signal, computing a pseudorange for each of four signal sources without performing signal tracking;
e) determining said location information based on the four said pseudoranges, without regard to the velocity of each of said signal sources. - View Dependent Claims (28)
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Specification