Inter-comparison of wave measurement by accelerometer and GPS wave buoy in shallow water off Cuddalore, east coast of India

Abstract

The performances of Accelerometer and GPS buoy were tested off Cuddalore at 30 m water depth during 15 to 30 November 2010 by mooring the buoys 225 m apart from each other. Compared to other wave parameters, results of regression analysis on significant wave heights (H_s) shows a better correlation (correlation coefficient R = 0.94) between accelerometer and GPS buoy. A lesser coefficient of R = 0.85 and 0.77 were resulted for wave direction and peak wave period (T_p) respectively. Waves were basically approaching from two directions, i.e. two wave forms or wave fields. One wave field was from around 80° and other was 140°. However, the wave directions averaged within each field over the

observation period individually are in good agreement with both buoys. It was noticed that the predominant directions reported by these buoys were not identical always. Even though the buoys were placed at identical water depths (~ 30 m) and in close proximity (~ 225 m), they were reporting different predominant directions. The correlation seems low because it was determined to a large extent, with waves from different directions. Comparatively, zero up-crossing wave period (T_z) shows a better agreement with T_p, which may not be a robust parameter due to its dependence on estimation of spectral peak.