Radar imaging mechanism of marine sand waves at very low grazing angle illumination

Ingo Hennings, Dagmar Herbers
Leibniz-Institut für Meereswissenschaften an der Universität Kiel
(IFM-GEOMAR), D-24148 Kiel, Germany
ihennings@ifm-geomar.de

ABSTRACT

Signatures of normalized radar cross section (NRCS) modulation at the ocean surface due to sea bottom topography are visible on a variety of radar images derived by shore- and ship-based radar as well as by real aperture radar (RAR) and synthetic aperture radar (SAR) on board air- and spaceborne platforms. The investigations carried out during 2002-2004 within several field experiments of the “Operational radar and optical mapping in monitoring hydrodynamic, morphodynamic and environmental parameters for coastal management (OROMA)” project have the objective to improve the effectiveness of new monitoring technologies such as shipborne imaging radars in coastal waters. The study area is the Lister Tief, a tidal inlet of the German Bight in the North Sea. Unique hydrodynamic effects associated with marine sand waves have been observed during ebb and flood tidal current phases. Up- and downwelling of the three-dimensional current field contribute too to the interaction between the flow and sea bed undulations. The shipborne coastal monitoring radar of the GKSS Research Center, Geesthacht, Germany, is based on a Kelvin Hughes RSR 1000 X-band (9.42 GHz) VV polarized river radar and was mounted on board the research vessel Ludwig Prandtl during the experiments. The important progress realized in this investigation is the availability of calibrated X-band radar data. Another aim of the project is to show the applicability of the quasi-specular scattering theory in combination with the weak hydrodynamic interaction theory for the radar imaging mechanism of the seabed. Simulated and measured NRCS modulations caused by marine sand waves have been compared and agree fairly well.

Last Update: 2005-03-15