Ambiguity Recovery for Long-Range GPS Kinematic Positioning

An ambiguity recovery technique for long-range GPS kinematic positioning is proposed for determining the integer ambiguities when cycle slips occur or the data gap is shorter than a few minutes. Two combined carrier phase observables (φ1 – φ2 and − 7φ1 + 9φ2) and precise pseudoranges are used to detect and remove cycle slips in the one-way carrier phase data, and subsequently validation criteria based on double-differenced carrier phase data are used to identify and validate the correct cycle slip values. If precise pseudoranges are not available, two combined carrier phase observables (φ1 – φ2 and − 3φ1 + 4φ2) and the predicted mobile receiver position are used to detect and remove cycle slips by means of a Kalman filter algorithm using an ambiguity function implementation. Results of an aircraft positioning experiment (baseline lengths of the order of 140 km) and a railway tracking experiment (baseline lengths of the order of 295 km) are presented.