GPS correction methods, apparatus and signals

A method for synthesizing GPS satellite measurements for a declared location, comprising:

• a. receiving network correction data for an epoch comprising:
• i. Satellite ephemeris data;
• ii. Satellite clock corrections;
• iii. Satellite ephemeris corrections;
• iv. Atmospheric parameters;
• and
• v. residual error corrections derived from one or more reference stations located within a vernier-cell region;
• b. determining whether the declared location is within the vernier-cell region;
• and
• c. applying the network correction data to determine, for each of a plurality of satellites during an epoch:
• estimated L1 and L2 pseudorange measurements from the satellite to the declared location;
• and estimated phase delays for L1 frequency, for L2 frequency, and for a frequency representing a frequency difference between the L1 frequency and the L2 frequency:

Apparatus having a processor for synthesizing GPS satellite measurements for a declared location and further comprising:

• a. a port for receiving network correction data for an epoch comprising:
• i. Satellite ephemeris data;
• ii. Satellite clock corrections;
• iii. Satellite ephemeris corrections;
• iv. Atmospheric parameters;
• and
• v. residual error corrections derived from one or more reference stations located within a vernier-cell region;
• b. software instructions to determine whether the declared location is within the vernier-cell region;
• c. software instructions to apply the network correction data to determine, for each of a plurality of satellites during an epoch:
• estimated L1 and L2 pseudorange measurements from the satellite to the declared location;
• and estimated phase delays for L1 frequency, for L2 frequency, and for the frequency difference between the L1 and L2 frequencies.

Apparatus for synthesizing GPS satellite measurements for a declared location, comprising:

• a. means for receiving network correction data for an epoch comprising:
• i. Satellite ephemeris data;
• ii. Satellite clock corrections;
• iii. Satellite ephemeris corrections;
• iv. Atmospheric parameters;
• and
• v. residual error corrections derived from one or more reference stations located within a vernier-cell region;
• b. means for determining whether the declared location is within the vernier-cell region;
• c. means for applying the network correction data to determine, for each of a plurality of satellites during an epoch:
• estimated L1 and L2 pseudorange measurements from the satellite to the declared location;
• and estimated phase delays for the GPS L1 frequency, for the GPS L2 frequency, and for a frequency representing a frequrency difference between the GPS L1 frequency and the GPS L2 frequency.

A method of determining a corrected GPS position fix, comprising:

• a. obtaining network corrections determined from measurements taken at a plurality of GPS reference stations and residual error corrections derived from one or more reference stations located within a vernier-cell region;
• b. for each of a plurality of satellites in view at a navigator location, receiving GPS ephemeris data and obtaining GPS receiver measurements;
• c. determining, from the GPS ephemeris data and the network corrections and the residual error corrections, calculated corrections appropriate to the navigator location for each of the plurality of satellites;
• d. applying the calculated corrections to the GPS receiver measurements to obtain corrected measurements;
• and
• e. computing a position fix from the corrected measurements.

Apparatus for determining a corrected GPS position fix, comprising:

• a. a GPS receiver to receive GPS ephemeris data and to obtain GPS receiver measurements for each of a plurality of satellites in view at a navigator location;
• and
• b. a navigation processor, responsive to network corrections determined from measurements taken at a plurality of GPS reference stations and residual error corrections derived from one or more reference stations located within a vernier-cell region, to
• i. Determine, from the GPS ephemeris data and the network corrections and the residual error corrections, calculated corrections appropriate to the navigator location for each of the plurality of satellites;
• ii. Apply the calculated corrections to the GPS receiver measurement to obtain corrected measurements;
• and
• iii. Compute a corrected GPS position fix from the corrected measurements.

Apparatus for determining a corrected GPS position fix, comprising:

• a. receiver means for receiving GPS ephemeris data and obtaining GPS receiver measurements for each of a plurality of satellites in view at a navigator location;
• b. processor means, responsive to network corrections determined from measurements taken at a plurality of GPS reference stations and residual error corrections derived from one or more reference stations located within a vernier-cell region, for
• i. Determining, from the GPS ephemeris data and the network corrections and the residual error corrections, calculated corrections appropriate to the navigator location for each of the plurality of satellites;
• ii. Applying the calculated corrections to the GPS receiver measurement to obtain corrected measurements;
• and
• iii. Computing a corrected GPS position fix from the corrected measurements.