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EARSeL: 2nd Workshop on Remote Sensing of the Coastal Zone Porto, Portugal, 9-11 June 2005 |
SESSION RADAR & OPTICAL MAPPING |
Nicole Braun, Friedwart Ziemer, Gottfried Schymura, Marius Cysewski
Institute for Coastal Research, GKSS Research Centre
21502 Geesthacht, Germany
nbraun@gkss.de
Coastal zone management demands for information on near shore hydrographic information to monitor e.g. currents, water depth, erosion or sedimentation, and coastline changes. The paper presents a time-efficient low cost solution for monitoring these parameters using remote sensing systems.
We want to introduce an X band radar system which can be operated from shore or from onboard a ship. The design of the system for the acquisition of different options (measurement of the Doppler-shift and the radar cross section (RCS)) is described. During several field experiments at the northernmost tip of the island of Sylt this radar system was used to measure the radar backscatter from a tidal inlet (Lister Tief) under different tide and wind conditions.
The results show different surface patterns on both the geocoded RCS and Doppler-velocity maps. These surface patterns are linked to oceanographic and atmospheric features: During ebb tide an eddy occurs close to the NE-tip of the island. Sea bottom topography signatures can be deduced by observing dynamic structures caused by divergences and convergences while tidal currents interact with subsurface sand waves. Stationary current shear signatures can be found. Wind direction impact on Doppler shift and wind streaks are visible. Even small-scale features like the impact of sheet pile walls perpendicular to the coast on currents were detected.
Using our radar system offers a possibility to monitor current fields. The range coverage depends on the height of the antenna. We acquired usable data up to 1 nm with an antenna at about 20 m above the sea surface. The spatial resolution is 7.5 m. Every 30 minutes data can be acquired. This combination of high spatial resolution and high sample frequency cannot be given by any other system.
Last Update: 2005-03-15