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Orthorectification of high resolution satellite images

The growing availability of high resolution satellite images leads to evaluations that are aimed at the definition of the mapping scale they can reasonably be defined for. The problems connected to the use of satellite images for the production of orthophotos in urban areas at a middle scale are dealt with in this work. An analysis of the residuals perspective errors connected to the presence of great altimetric discontinuites due to buildings and infrastructures is made. The effects of the use of a Dense DTM are evaluated and the problem of displacements on orthophotos induced by raised volumes are considered too. A procedure has been developed which allows the orthoprojection of high resolution satellite images using a Dense DTM and nonparametric models. In particular non parametric algorithms based on Rational Function Models (RFM) and Neural Network (Multy Layer Perceptron) have been implemented. A multi-image (along-across track stereo images, multi-temporal images) and/or multisensor approach can be followed for the production of true orthophotos: this approach can prevent from the problem of data duplication next to elevation discontinuites. * Corresponding author.