Stereoscopic observation of 3-D images - A help to the interpretation of remote sensing data

Knowledge of the relief is essential for the making-up, updating and use of numerical databases in such fields as Geographic Information System, topog raphic and thematic mapping, Topographic data acquisition, on land or deep- sea environment, has been made greatly easier by the development of specifi c algorithms that can compute, in a routine way, Digital Elevation Models. DEM are generated on the basis of x-y-z grid points acquired during seismic or bathymetric and topographic surveys. They can also be computerised from digitised maps or stereoscopic remote sensing images. Several 3-D display techniques are now in use and are of great interest especially in quantitat ive geomorphology and structural geology. Recently, laser technology has im proved in a drastic way the altimetry data and can be used for off-shore pu rposes until tenth of meters under good conditions with an accuracy of seve ral centimetres. This article deals briefly with the stereoscopic methodology, both on optic and radar remote sensing data; the different 3-D display techniques are ex plained and illustrated by some examples.