Today more and more space sensors are available that acquire not only stereo but also tri-stereo satellite imagery. Beginning with the year 1986, when SPOT-the first satellite providing stereo-images, with a panchromatic Ground Sampling Distance (GSD) of 10 m-was launched, the optical satellite industry has been experiencing continuous development. In the case of the WorldView-3 derived DSM, the estimated height of small vehicles, buildings, and trees (lengths 33 pixels, crown diameters >16 pixels) were reconstructed at more than 90% in height.ДЇor more than thirty years, civilian satellite sensors have been used for digital elevation model (DEM) extraction over large areas in a timely and cost-effective manner for a wide range of applications in engineering, land planning, and environmental management. For small vehicles, buildings, and trees (lengths 14 pixels, crown diameters >7 pixels), the estimated heights were higher than 60% of the real values.

Starting from very small objects, which are not elevated against their surroundings, and ending with large objects, we obtained a gradual increase of the relative heights. We demonstrate that the DSM-based estimated height of a single object strongly depends on its size, and we quantify this effect. Manually measured object heights from the oriented images were used as a reference. The estimated height was investigated with respect to the following parameters: building length and width, vehicle length and width, and tree crown diameter. The main focus is to quantify their detectability in the photogrammetrically-derived DSMs by estimating their heights as a function of object type and size. For this purpose, single buildings, vehicles, and trees were analyzed. This study investigates the capabilities and limitations of space-borne very high resolution imagery, specifically PlГ©iades (0.70 m) and WorldView-3 (0.31 m) imagery, with respect to the automatic point cloud reconstruction of small isolated objects. Dense image matching is a key component in 3D reconstruction and mapping, although the 3D reconstruction process encounters difficulties for water surfaces, areas with no texture or with a repetitive pattern appearance in the images, and for very small objects.

High-resolution stereo and multi-view imagery are used for digital surface model (DSM) derivation over large areas for numerous applications in topography, cartography, geomorphology, and 3D surface modelling.

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