Method and system for resolving double difference GPS carrier phase integer ambiguity utilizing decentralized Kalman filters

Claim 1

A method for accurately determining the position coordinates of a mobile GPS receiver with respect to the earth's surface, said method comprising the steps of: receiving at a reference station which is located at precisely known coordinates a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequency; calculating carrier phase data and a pseudorange with respect to each received GPS satellite from the reference station; receiving at said mobile GPS receiver a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequency; calculating carrier phase data and a pseudorange with respect to each received GPS satellite from said mobile GPS receiver; applying GPS satellite ephemeris parameters and the calculated pseudoranges to a first Kalman filter to obtain an error state vector for position and time; applying GPS satellite ephemeris parameters and said calculated carrier phase data to a second Kalman filter to obtain a predicted vector of velocity and clock rate error; estimating line of sight range and range rates to each GPS satellite from the mobile GPS receiver utilizing the outputs of the first and second Kalman filters; calculating double difference phase measurements utilizing carrier phase data received from at least two GPS satellites; resolving carrier wave integer ambiguity utilizing said estimated line of sight range and range rates and said double difference phase measurements in order to calculate an accurate set of coordinates for said mobile GPS receiver; and periodically updating position coordinates for said mobile GPS receiver based upon said resolved carrier wave integer ambiguity and subsequent carrier phase variations.

Claim 2

A method for accurately determining the position coordinates of a mobile GPS receiver with respect to the earth's surface, said method comprising the steps of: receiving at a reference station which is located at precisely known coordinates a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequency; calculating carrier phase data and a pseudorange with respect to each received GPS satellite from the reference station; receiving at said mobile GPS receiver a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequency; calculating carrier phase data and a pseudorange with respect to each received GPS satellite from said mobile GPS receiver; applying GPS satellite ephemeris parameters and the calculated pseudoranges to a first Kalman filter to obtain an error state vector for position and time; applying GPS satellite ephemeris parameters and said calculated carrier phase data to a second Kalman filter to obtain a predicted vector of velocity and clock rate error; estimating line of sight range and range rates to each GPS satellite from the mobile GPS receiver utilizing the outputs of the first and second Kalman filters; calculating double difference phase measurements utilizing carrier phase data received from at least two GPS satellites; resolving carrier wave integer ambiguity utilizing said estimated line of sight range and range rates and said double difference phase measurements in order to calculate an accurate set of coordinates for said mobile GPS receiver; and periodically updating position coordinates for said mobile GPS receiver based upon said resolved carrier wave integer ambiguity and subsequent carrier phase variations.

Claim 8

A system for determining the position coordinates of a mobile GPS receiver with respect to the earth's surface, said system comprising: a reference station located at precisely known coordinates for receiving a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequency; means within said reference station for calculating carrier phase data and a pseudorange with respect to each received GPS satellite from the referenced station; a mobile GPS receiver for receiving a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequencies; means within said mobile GPS receiver for calculating carrier phase data at a pseudorange with respect to each received GPS satellite from said mobile GPS receiver; a communication link for interconnecting said reference station and said mobile GPS receiver; a first Kalman filter within said mobile GPS receiver for operating on GPS satellite ephemeris parameters and calculated pseudoranges from both said reference station and said mobile GPS receiver to each received GPS satellite to obtain an error state vector for position and time; a second Kalman filter within said mobile GPS receiver for operating on GPS satellite ephemeris parameters and calculated carrier phase data from both said reference station and said mobile GPS receiver to obtain a predicted vector of velocity and clock rate error; processor means within said mobile GPS receiver for estimating line of sight ranges and range rates to each GPS satellite from the mobile GPS receiver utilizing outputs of the first and second Kalman filters; means for calculating double difference phase measurements utilizing carrier phase data received from at least two GPS satellites; means for resolving carrier wave integer ambiguity utilizing said estimated line of sight ranges and range rates and said double difference phase measurements in order to calculate an accurate set of coordinates for said mobile GPS receiver; and means for periodically updating position coordinates for said mobile GPS receiver based upon said resolved double difference carrier wave integer ambiguity and subsequent carrier phase variations.

Claim 9

A system for determining the position coordinates of a mobile GPS receiver with respect to the earth's surface, said system comprising: a reference station located at precisely known coordinates for receiving a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequency; means within said reference station for calculating carrier phase data and a pseudorange with respect to each received GPS satellite from the referenced station; a mobile GPS receiver for receiving a plurality of GPS satellite signals which each comprise a pseudo random noise (PRN) code containing implicit clock data modulated on a carrier wave of known frequencies; means within said mobile GPS receiver for calculating carrier phase data at a pseudorange with respect to each received GPS satellite from said mobile GPS receiver; a communication link for interconnecting said reference station and said mobile GPS receiver; a first Kalman filter within said mobile GPS receiver for operating on GPS satellite ephemeris parameters and calculated pseudoranges from both said reference station and said mobile GPS receiver to each received GPS satellite to obtain an error state vector for position and time; a second Kalman filter within said mobile GPS receiver for operating on GPS satellite ephemeris parameters and calculated carrier phase data from both said reference station and said mobile GPS receiver to obtain a predicted vector of velocity and clock rate error; processor means within said mobile GPS receiver for estimating line of sight ranges and range rates to each GPS satellite from the mobile GPS receiver utilizing outputs of the first and second Kalman filters; means for calculating double difference phase measurements utilizing carrier phase data received from at least two GPS satellites; means for resolving carrier wave integer ambiguity utilizing said estimated line of sight ranges and range rates and said double difference phase measurements in order to calculate an accurate set of coordinates for said mobile GPS receiver; and means for periodically updating position coordinates for said mobile GPS receiver based upon said resolved double difference carrier wave integer ambiguity and subsequent carrier phase variations.