My research interests centre about the use of Global Navigation Satellite Systems (GNSSs), most notably GPS, for a multitude of precise positioning and navigation applications. Specific application areas include crustal deformation monitoring, precise orbit determination, and precise positioning of offshore platforms. This research requires development of positioning algorithms, which include filters, functional models, stochastic models, and prediction models to mitigate physical affects. Recent algorithm research has focused on improving the robustness of precise point positioning, and extending the range of single-baseline, real-time kinematic (RTK) GPS.