Instantaneous Ambiguity Resolution for Medium-Range GPS Kinematic Positioning Using Multiple Reference Stations

A linear combination functional model, formed from the single-differenced functional equation for baselines from a mobile receiver to three or more reference receivers, is proposed, in which the orbit bias and ionospheric delay can be eliminated, and, in addition, the tropospheric delay, multipath and observation noise can be significantly reduced. As a result, the ambiguity resolution technique that can be employed for medium-range GPS kinematic positioning is similar to that used for the short-range case. Kinematic tests have been carried out in Sydney, Australia, with separations from the nearest reference stations greater than 30km. The carrier phase ambiguities can be resolved for every epoch and the success rate (correct identification of the integer ambiguities) was 100%. This technique is well suited to real-time precise GPS kinematic positioning.