US Patent 9146319 GNSS signal processing with rover ambiguity fixing

Methods and apparatus are described for processing a set of GNSS signal data derived from signals of a set of satellites having carriers observed at a rover antenna, wherein the GNSS signal data includes a carrier observation and a code observation of each carrier of each satellite, comprising: obtaining for each satellite clock corrections comprising at least two of: (i) a code-leveled satellite clock, (ii) a phase-leveled satellite clock, and (iii) a satellite clock bias representing a difference between a code-leveled satellite clock and a phase-leveled satellite clock, running a first filter which uses at least the GNSS signal data and the clock corrections to estimate values for parameters comprising at least one carrier ambiguity for each satellite, and a covariance matrix of the carrier ambiguities, determining from each carrier ambiguity an integer-nature carrier ambiguity comprising one of: an integer value, and a combination of integer candidates, inserting the integer-nature carrier ambiguities as pseudo-observations into a second filter, and running the second filter which uses at least the GNSS signal data and the clock corrections to obtain estimated values for parameters comprising at least the position of the receiver.