Offshore Winds and Currents Observation by GPS Buoy with Numerical Filtering Analysis

This paper introduces basic design of the GPS buoy multi-purpose data processing system for offshore information. The system consists of real-time tsunami detection, directional wave analysis, infragravity wave analysis, offshore wind observation, and current observation. For real-time tsunami detection, applicability of the GPS buoy system using the proposed numerical filtering techniques was confirmed with the prototype observation during 2004 Tokaido-off Earthquake Tsunami event. The GPS buoy system is able to distribute directional wave information within the corresponding wave periods of between 6 and 30 seconds, using the frequency banded spectrum analysis method. Offshore winds data were compared with that of on-land station at 225 m high on the Muroto-Misaki. It was found that buoy motion correction is necessary only when we need instantaneous maximum wind speed. GPS buoy is also able to observe offshore currents by the frequency banded analysis.