Long-Baseline (> 1000 km), Sub-Decimeter Kinematic Positioning of Buoys at Sea, with Potential Application to Deep-Sea Studies

GPS data from two experiments in positioning buoys at sea have been processed using a precise, long-range, differential, kinematic technique. In each case the data were collected for more than three hours both at a buoy and at a nearby coastal site (in Llafranc, Spain, and in Duck, USA) at a high rate (1-2 Hz), along with measurements from neighboring tidal stations, to verify the estimated heights. A precise, short-range trajectory was computed for each buoy, relative to the nearby coastal site. The trajectory of each buoy was re-calculated relative to distant reference sites, some more than 1000 km away (IGS stations in Europe, CORS stations in the USA). In both cases the 3-dimensional (r.m.s.) difference between short and long-range position fixes was less than 10 cm over three hours. The use of a simple constraint on the buoy's mean height variability greatly speeded up the convergence of the navigation Kalman filter.