Long baseline 3 frequency differential GNSS

Ambiguity resolution is the key to fast high-precision relative GNSS positioning. Once the ambiguities have been resolved successfully as integers, the corresponding carrier phase measurements will start to act as if they were high precision range measurements, thereby allowing the parameters of interest, such as baseline-coordinates, to be estimated with a comparable high precision. In order to enhance the ambiguity resolution performance, both modernised GPS and the future European Galileo system are intended to transmit signals on three instead of two navigational frequencies. In this contribution the ambiguity resolution performance of the current two-frequency GPS and the modernised three-frequency GPS are analyzed for long baselines, i.e. baselines for which the atmospheric distortions can not be neglected.