The use of a GPS-equipped buoy for water level determination

In recent years, Global Positioning System (GPS) receivers have been placed on buoys to determine sea surface height. The Naval Oceanographic Office (NAVOCEANO) has become interested in this application for tides work and has sponsored a series of GPS buoy experiments in Mississippi coastal waters. The primary goal of the experiments was the determination of water level with GPS using the WGS84 reference ellipsoid as a tidal benchmark. Also of importance was the determination of the minimum buoy sensor configuration (aside from GPS) required to accomplish this measurement, and to evaluate RTK GPS performance over time and distance. The fully integrated buoy was deployed in 2001, 2002, and 2003. The 2001 RTK results were analyzed for solution availability, solution quality, and solution correlation with other sensor output. Solution availability was high during buoy operational periods; however, the solution quality was hampered by an apparent GPS filter-based anomaly in the receiver RTK processing. Tide gauge comparison indicated subdecimeter-level water level recovery was attainable. Initial processing of 2002 data produced cm-level differences between RTK and tide gauge water levels. These initial results show great promise for the use of RTK buoys in water level recovery, and more data collection and analysis will be undertaken with the 2003 deployment.