Method of determining a GPS position fix and a GPS receiver for the same
A method of determining a GPS position fix is disclosed together with a corresponding GPS receiver and server for the same. The method comprising the steps of: (i) providing standard GPS ephemeris corresponding to that transmitted by a GPS satellite; (ii) providing supplemental GPS ephemeris including at least one parameter describing the fluctuation over time of at least one satellite orbit parameter of standard GPS ephemeris; (iii) measuring psuedoranges to GPS satellites; and (iv) determining a GPS position fix from both the standard and supplemental GPS ephemeris provided in steps (i) and (ii) respectively and the psuedoranges measured in step (iii).
1. A method of determining a GPS position fix comprising the steps of:
providing standard GPS ephemeris corresponding to that transmitted by a GPS satellite;
generating supplemental GPS ephemeris at a GPS navigation device, the supplemental GPS ephemeris comprising at least one parameter describing the fluctuation over time of at least one satellite orbit parameter of the standard GPS ephemeris;
measuring pseudoranges to GPS satellites; and
determining a GPS position fix for the GPS navigation device from at least one of a plurality of data, the plurality of data comprising the standard and supplemental GPS ephemeris and the pseudoranges.
2. A method according to claim 1 wherein the supplemental GPS ephemeris includes at least one parameter describing a frequency component of the fluctuation over time of at least one satellite orbit parameter of standard GPS ephemeris.
3. A method according to claim 2 wherein the or at least one of the frequency components corresponds to a lunar cycle.
4. A method according to claim 2 wherein the or at least one of the frequency components corresponds to a solar cycle.
5. A GPS receiver configured to determine a GPS position fix from standard GPS ephemeris corresponding to that transmitted by a GPS satellite;
supplemental GPS ephemeris including at least one parameter describing the fluctuation over time of at least one satellite orbit parameter of the standard GPS ephemeris; and
pseudoranges measured from the GPS receiver to GPS satellites.
6. A GPS receiver according to claim 5 wherein the supplemental GPS ephemeris includes at least one parameter describing a frequency component of the fluctuation over time of at least one satellite orbit parameter of standard GPS ephemeris.
7. A GPS receiver according to claim 6 wherein the or at least one of the frequency components corresponds to a lunar cycle.
8. A GPS receiver according to claim 6 wherein the or at least one of the frequency components corresponds to a solar cycle.
9. A GPS receiver according to claim 5 further configured to determine at least one parameter of the supplemental GPS ephemeris from a history of standard GPS ephemeris received directly from the GPS satellites by the GPS receiver.
10. A server configured to transmit to a remote GPS receiver supplemental GPS ephemeris including at least one parameter describing the fluctuation over time of at least one satellite orbit parameter of standard GPS ephemeris corresponding to that transmitted by a GPS satellite, the supplemental ephemeris generated by an equation of the form:
P=C 1 +C 2 t+C sun (cos(2 πf sun t+φ sun )) +C moon (cos(2 πf moon t+φ moon ))
wherein P is a satellite orbit parameter, C 1 , C 2 , C sun , C moon , φ sun , and φ moon are constants based on the standard GPS ephemeris, t is the time since the beginning of the year and:
f
sun
=
1
182.5
days
,
and
f
moon
=
1
13.7
days
.
11. A server according to claim 10 wherein the supplemental GPS ephemeris includes at least one parameter describing a frequency component of the fluctuation over time of at least one satellite orbit parameter of standard GPS ephemeris.
12. A server according to claim 11 wherein the frequency component corresponds to a lunar monthly cycle.
13. A server according to claim 11 wherein the frequency component corresponds to a yearly cycle.
14. A method according to claim 1 , wherein providing the supplemental GPS ephemeris at the GPS navigation device comprises implementing an equation of the form:
P=C 1 +C 2 t+C sun (cos(2 πf sun t+φ sun )) +C moon (cos(2 πf moon t+φ moon ))
wherein P is a satellite orbit parameter, C 1 , C 2 , C sun , C moon , φ sun , and φ moon are constants based on the standard GPS ephemeris, t is the time since the beginning of the year and:
f
sun
=
1
182.5
days
,
and
f
moon
=
1
13.7
days
.
15. A method according to claim 1 , wherein providing the standard GPS ephemeris comprises transmitting the standard GPS ephemeris from the satellite directly to the GPS navigation device.
16. A server according to claim 10 , wherein the remote GPS receiver is further configured to determine at least one parameter of the supplemental GPS ephemeris from a history of standard GPS ephemeris received directly from the GPS satellites by the remote GPS receiver.
17. A server according to claim 10 , wherein the standard GPS ephemeris is transmitted from the satellite directly to the remote GPS receiver.