Investigation of the potential of multiscopic VHR satellite imagery for the production of 3D models of complex urban areas

Objectives of the Belspo research project MAMUD are to investigate how earth observation can contribute to a better monitoring, modeling and understanding of urban dynamics, and its impact on the urban and suburban environment. The outcome of the research can lead to the develop-ment of a useful tool for urban planning approaches based on sustainable development. While most remote sensing based studies on urban dynamics only consider two-dimensional structure, in this research stereoscopic and as an addition to standard photogrammetry, multi scopic imagery will be used to derive the third dimension, which is obviously important in describ-ing urban morphology. Improved radiometric quality and geometric accuracy of high resolution sensors like Ikonos and Quickbird allow a more detailed mapping of urban areas. Due to this new generation of sensors the potential for producing surface models of such complex areas has substantially increased. In this treatise the discussion of a methodology and results of semi-automatic city DSM extraction from an Ikonos triplet, is introduced. Built-up areas are known as being complex for photogram-metric purposes, partly because of the steep changes in elevation caused by buildings and urban features. To make DSM extraction more robust and to cope with the specific problems of height displacement, concealed areas and shadow, a multi-image based approach is followed. For the VHR tri-stereoscopic study an area extending from the centre of Istanbul to the urban fringe is chosen. The multiple image dataset consists of one Ikonos stereo pair combined with a nearly vertical Ikonos image from more or less the same orbit. The Ikonos stereo pair, epipolar projected, is cap-tured in March 2002. The images of the stereo pair have an elevation angle of respectively 67.59° and 75.59°. The collection azimuth is respectively 1.6° and 214.1°. The third image, captured in May 2005, has an elevation angle of 80.93° and a collection azimuth of 23.5°. Research will concentrate, in first phase on the development of methods to optimize the extrac-tion of photogrammetric products from the bundled Ikonos triplet. Optimal methods need to be found to improve the radiometry and geometry of the imagery, to improve the semi-automatically derivation of DSM’s and to improve the postprocessing of the products. Secondly we will also investigate the possibilities of creating stereo models out of images from the same sensor taken on a different date, e.g. one image of the stereo pair combined with the third image. Finally the photogrammetric products derived from the Ikonos stereo pair as well as the products created out of the triplet and the constructed stereo models will be investigated by comparison with a 3D ref-erence. This evaluation should show the increase of accuracy when multi-imagery is used instead of stereo pairs