Surface wave measurements using a ship-mounted ultrasonic altimeter

We present a method for measuring one-dimensional surface wave spectra using a ship-mounted ultrasonic altimeter in combination with a motion correction device. The instruments are mounted at the bow of the ship and provide high-resolution, local, wave information. We present results from three recent field studies. The results are compared with data from a conventional waverider buoy and, when in-situ observations are not available, with wave model analyses and satellite altimetry. We find good agreement with regard to integrated parameters such as significant wave height and mean period. Comparison with a waverider demonstrates fair agreement with regard to spectral shape, but the representation of the low frequency part depends on the quality of the motion correction data.