LANDMAP: CREATING A DEM OF THE BRITISH ISLES BY SAR INTERFEROMETRY

摘要

The LANDMAP project will provide an integrated set of mosaiced SPOT and Landsat-TM images of the British Isles. ortborectified to be easity accessible in a geographical co-ordinate system. In order to orthorectify the imagery (which comes from an archive held for UK academic use). a digital elevation model (DEM) is first needed, A stated aim of the LANDMAP project is that its products should be free of onward copyright or licensing issues, This means that most usual elevation data sources were unsuitable. A first stage of the project is therefore to create a now DFM of the British isles using the remote sensing technique of synthetic aperture radar (SAR) interferometry (IfSAR), This is to be accomplished in two passes: firstly creating an initial DEM from a minimal coverage of the British Isles by ERS SAR data for initial quality checking (presented here), followed by full DEM creation from three coverages. Full DEM creation involves the interferometric processing, phase unwrapping and orthorectification of pairs of acquisition strips of SAR data. It is then necessary to average together the individual DEMs from separate pairs to provide an optimum DEM for each strip. The strips are then fitted together across the British Isles using a block-adjustment scheme. A range of kinematic GPS profiles were acquired across the British Isles in Septemger 1999 for quality assessment of intermediate and final DEMs. We demonstrate good agreement in planimetric positions without the use of control points and elevation difference standard deviations of the order of 10m.