True Orthophotos are the optimal base for mapping applications – in particular for airborne imaging projects. By delivering an orthographic image where each pixel coordinate is known in the reference frame, it can be used to perform feature extraction or to overlay GIS data. In contrast to the original imagery, no additional information about the terrain height is required. Furthermore, relief displacement is compensated – which is also the major benefit in contrast to classical ortho production based on Digital Terrain Models.
In order to create a True Orthophoto, a precise Digital Surface Model is required, which not only provides dense ground information but also the surface of all objects such as the height of buildings or vegetation. This Digital Surface Model needs to be known for each pixel of the image, since it is subsequently used to remove the displacement caused by the relief. In particular the quality of the edges is of importance for high quality end products, where the SURE dense image matching engine is well suited due to its performance on the retrieval of 3D surfaces regarding density and edge precision.