3 remoteote sensing methods for obtaining information on sea bottom topography have been investigated: passive optical bathymetry, sunglint observation and radar observation. Optical and microwave remotely sensed data as well as extensive in situ data, including a detailed bathymetric map, were gathered in a sand wave area off the Dutch coast. These data were compared with each other and with model predictions. The models are based on the current state of the art, with some extensions. Passive optical bathymetry has limited use above the North Sea because of its limited depth range. Sunglint observation of bottom topography is possible, but its practical applicability is limited by the requirement of low wind speeds and cloudless weather. Radar observation with an imaging radar operating at long wavelengths has the highest potential. The agreement between radar data and model predictions is not always good, due to lack of knowledge on the basic processes. However, in cases where there is good agreement, the imaging model can be inverted numerically to retrieve depth information from radar images.
Numerical models for the dynamic behaviour of the sea floor are currently being developed. These models need information on the sea bottom topography for their calibration and validation. Traditional bathymetric surveys are time and cost consuming. Remote sensing methods, however, can give information about the sea bottom over large areas at relatively low costs. In this project the mapping of the sea bottom in shallow seas will be studied with microwave and optical sensors. It is known that wave-current interactions cause roughness variations at the sea surface which can be detected both with imaging radar and with optical sensors. The usability of this phenomenon will be investigated in terms of mapping accuracy and resolution by performing an experiment in a sand wave region off the Dutch coast. Comparison of the experimental results to predictions from numerical models based on existing knowledge of the imaging mechanisms will yield important information about our understanding of the processes involved. This understanding is crucial for the development of routine procedures in other projects.
Funding SchemeCSC - Cost-sharing contracts
2600 MH Delft
LL57 2DG Bangor (Gwynedd)