Modelling topography with SAR interferometry: illustrations of a favourable and less favourable environment

Radar remote sensing has faced an increasing interest in a wide variety of Earth observation studies during this last decade. This interest is notably related to the necessity to map areas where the cloud cover does not allow the use of classical optical sensors, or the increasing interest for ocean studies. Amongst the large number of radar applications different techniqu es exist for mapping the topography. Digital elevation models (DEMs) are re quired in a growing field of applications and especially in earth sciences where their use in structural geology, environmental geology or engineer ge ology has become essential. In this paper, we discuss the results obtained with SAR interferometry (InSAR) from two different environments and for two specific applications. The first is the study of the recent and present da y tectonic evolution of the Rukwa rift (SW Tanzania) and the other, the stu dy of the topography from the Bulusan volcano (Philippines). In the first s ituation, interferometry gave encouraging results. The computed InSAR DEM h elped to identify unsuspected lineaments closely related to tectonic. In th e Philippines. SAR interferometry failed to provide DEM because of the temp oral decorrelation due to the dense vegetation and the humid climate. Radar grammetry or radar stereoscopy was tested with few different geometries, bu t the obtained results were evidencing the need in accurate ground control points. Discrepancies with regard to the reference computed from existing 1 /50,000 topographic maps are reported to be larger where no or too few GCPs were identified. (C) 2001 Elsevier Science Ltd. All rights reserved.