GPS Ambiguity Resolution and Validation: Methodologies, Trends and Issues

Resolving the GPS carrier-phase ambiguities has been a continuing challenge for sub-centimeter-level highprecision GPS positioning. Once the integer ambiguities are fixed correctly, the carrier-phase observations are conceptually turned into sub-centimeter-level high-precision range measurements making it possible to attain high-precision positioning solutions. Consequently, this topic has been a rich source of GPS-research over the last decade. A brief review of the previous work on ambiguity resolution and validation which has been carried out by many research groups from all over the world is presented in this paper. For a general understanding of these contributions, we have classified the ambiguity resolution techniques in terms of their characteristics. Current research trends and issues in ambiguity resolution and validation are described and a bibliography of representative papers is provided.