Simultaneous Measurements From Buoys and Vessel-Mounted X-Band Radar to Study Currents and Waves at Breisundet Field

Abstract

Estimation of ocean wave conditions is extremely crucial for the planning and execution of demanding marine operations. Further, response-based decision-making requires accurate wave inputs to derive the responses using a numerical model. X-band marine radars, installed on top of the vessels, are cost-effective means to assess the incoming wave field by means of backscattered intensity images. Dedicated full-scale measurements were conducted using the research vessel Gunnerus in the Breisundet field, located on the west coast of Norway. The results were validated using the collocated buoy and acoustic Doppler current profiler (ADCP). The introduction of an additional step in the least-squares estimation with an adaptive threshold based on the signal-to-noise ratio improved the estimation of radar-based current estimates. The radar-based current estimates show close agreement with the ADCP-based currents with a root mean-squared error of 0.06. The spectra at the mid-range gave the best results when studying the effects due to range dependency. A semiempirical modulation transfer function (MTF) function created using a fifth-order polynomial fitting was found to accurately reproduce the empirical MTF. Overall, the scaled wave spectrum from the radar exhibits good agreement with the buoy measurements.