Forming digital elevation models from single pass SPOT data: results on a test site in the Indian Ocean

Digital elevation models are significant elements in most of the remote sensing field, mostly as auxiliary data and sometimes as primary source of scientific or commercial information. The use of SPOT data opened a new era in the DEM computing business by allowing the construction of good precision DEMs (typically 10m rms) thanks to its sidelooking capability. Alternate techniques are now available, such as SAR interferometry. Not all applications, however, require high precision DEM. The authors report the accuracy of a DEM made from two images acquired by the same optical instrument at the same time (single pass stereoscopy). This experiment is characterized by a very small forward baseline of about 15 km. The geometric performance is attenuated by a factor of about 100 with respect to conventional SPOT stereoscopy. Another potential difficulty is the different nature of the two images: 20m single band image and 10m panchromatic image. On the other hand, single pass operation guarantees a very good similarity between the images and a minimal influence of cloud cover. The concept has been tested using data acquired over l´ile de la Reunion, off the coast of Madagascar, a typical area where collecting stereoscopic data is difficult. The authors use a high performance image correlator that they developed, which compensates partially for the poor baseline available. They discuss the quality of the result, which is compared to a conventional DEM, as well as the potential of this new product, from the point of view of the applications and of the design of future missions