Speeding Up CORS Network RTK Ambiguity Resolution

An efficient way for the real-time GNSS data processing of CORS stations is to make use of a Kalman filter implementation. Using dual-frequency un-differenced carrier phase and code data as observations, the state vector consists of troposphere zenith delays, differential ionosphere delays, receiver and satellite clock errors and phase ambiguities. Satellite positions are computed in real time based on the predicted part of the ultrarapid IGS orbits. No receiver positions are present in the state vector since these are precisely known for permanent reference stations. In the Kalman filter time-update the float ambiguities are predicted to be constant (provided that no cycle slips occur). The integer ambiguities are then resolved by means of the LAMBDA method, but only after the precision of the float ambiguity solution has sufficiently converged.