Shallow water bathymetry derived from an analysis of X-band marine radar images of waves

Image sequences of surface gravity waves are readily produced by standard m arine X-band radars. These image sequences contain a great deal of informat ion regarding wave parameters and their variation over an area. By approach ing the analysis of such data, using image analysis techniques. it is possi ble to map the variations in wave behaviour in a shallow water area. Wave c elerity and direction can he mapped, and inversion algorithms based on line ar wave theory used to infer the underlying bathymetry. Knowledge of the pe riod of the waves is necessary for the analysis. and this can also be calcu lated from the radar data, although there is some discrepancy between the f igures derived from radar data and from an offshore S4DW instrument. These discrepancies are investigated, and the results presented. Three days of da ta from the Holderness II deployment during 1995 have been analysed, and es timates of the bathymetry produced. The calculated depths show a mean water level comparable to that read off an Admiralty chart for the area, and a t idal signal is also clearly superimposed on the data, giving confidence in the water depths derived using this technique. (C) 1999 Elsevier Science B. V. All rights reserved.