Evaluation of a GNSS for wave measurement and directional wave spectrum analysis.

Wave buoys are important devices to monitor and analyze wave data for ocean and coastal engineering. A GNSS wave buoy is briefly introduced in the paper, which has high resolution to measure the buoy motion by vertical, north-south and west-east displacements and independent velocities in above three directions. Based on the displacements and velocities, statistical results, frequency spectra and directional spectra are analyzed, and results based on the displacements are compared with that from Waverider with a distance less than 6m deployed in the special sea water with the GNSS buoy. Wave profiles comparison show that GNSS buoy presented slightly large significant wave height and mean wave height due to its high sampling frequency, and resulted in smaller mean wave period than that from Waverider. Statisticaly, between the analyzing result of the GNSS and wave rider, the maximum error of wave height is about 5.5%; and the maximum difference of wave period is about 0.5s, when sampling frequency is similar. The energy spectra were basically consistent from these two devices. The peaks of directional spectra were similar but the spreading angle was smaller from GNSS. Results mean the GNSS device presents almost similar wave information to that from Waverider. • Time history of displacement of a GNSS wave buoy and a Waverider with distance about 6m is comparable. • Displacements and velocities are contributed to form directional wave spectrum for GNSS measuring data. • Statistically the mean wave height coincident; by GNSS H 1/10 and H 1/3 slightly higher, mean wave period less about 15%–20%. • From spectrum analysis, H s is about 2%–4% higher and T ave is about 15% less by GNSS; peak frequency is very close. • The difference of wave direction by two buoys at f P is within 16°; S P is less about 25–52° and is 25% higher by GNSS. [ABSTRACT FROM AUTHOR]