EARSeL 2000 - Topic: Water applications - Coastal Zones

Comparison of a Digital Elevation Model with extracted coastlines from ERS and IRS satellite data

by Danielle Hoja1, Edzard Romaneeßen2, Susanne Lehner2, Norbert Winkel3

1Institut für Kartographie, TU Dresden, 01062 Dresden, Germany
2Deutsches Fernerkundungsdatenzentrum, DLR e.V., 82234 Weßling, Germany
3Bundesanstalt für Wasserbau, 22559 Hamburg, Germany

For geoscientific applications it is of high interest to investigate and visualise the surface of the earth and its changes. A focal point of natural hazard management support is therefore the temporary movement of geomorphological structeres in coastal regions. For continuous investigations the use of RADAR data has been proven to be fit best. A great number of potential users in the area of public administration has shown interest on an operational analysis of Radar data for their tasks/business, like the Federal Waterway Engineering and Research Institute (BAW), which supported this work.

The aim of the work presented in this paper is to compare the work done in this field by different partners. The data are a digital elevation model, extracted coast lines and coherency maps. The investigation area lies in the mud flats of the estuaries of the rivers Elbe and Weser in the German Bight. The work was structured into two main parts: investigation of the different data and methods used and the actual comparison of the results.

The digital elevation model is a result of the interferometric analysis of the airborne data of the AeS1 sensor. The sensor is developed and used by Aerosensing Radarsysteme GmbH which has also done the work to derivate and validate the High Precision Topography Model of the Waddensea. Coherency data of the ERS Tandem Mission in 1995 and 1996 is used for coastline extraction, the different levels of coherency of land and sea is used therefore. Further examinations have been carried out to find out what the areas of high coherency in the tidal flats mean which occured unexpectedly in the data. With coastline extraction from coherency data only the line of the highest water level between the two images can be achieved. To get the actual water-land-line in ERS-images at the recording time investigations of the TIDE project (Synergy of remote sensing data and mathematical tide models in order to optimise the diverging claim of use of estuaries) have been drawn into consideration. For comparison purposes also extracted coastlines from optical data through mudflat classification were used.

The comparison of the results will show, that the different results are matching, even with the different resolutions. So for further investigations e.g. with mathematical tide models the ERS-data with the coarse resolution can be used for an overview. And where finer resolutions are needed it is possible to replace the data with the airborne DEM, which only is derivated for small areas.

The work has been done at and with support of Aerosensing Radarsysteme GmbH, Oberpfaffenhofen, Germany.

Remarks, requests, criticism or just a mail to: danielle@markhoja.de