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 marine X-band radars. These image sequences contain a great deal of information regarding wave parameters and their variation over an area. By approaching the analysis of such data, using image analysis techniques, it is possible to map the variations in wave behaviour in a shallow water area. Wave celerity and direction can be mapped, and inversion algorithms based on linear wave theory used to infer the underlying bathymetry. Knowledge of the period of the waves is necessary for the analysis, and this can also be calculated from the radar data, although there is some discrepancy between the figures derived from radar data and from an offshore S4DW instrument. These discrepancies are investigated, and the results presented. Three days of data from the Holderness II deployment during 1995 have been analysed, and estimates 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 tidal signal is also clearly superimposed on the data, giving confidence in the water depths derived using this technique.