Photogrammetric Systems

Research Activities and Projects

Direct Georeferencing of UAS Platforms Direct Georeferencing of UAS Platforms

The use of integrated GNSS/inertial systems is well-known and established in the traditional large-format airborne mapping since years. Recent commercially available unmanned aircraft systems (UAS) now also offer this technology, mostly reduced to the precise trajectory computation using differential GNSS for positioning. If one reduces the direct georeferencing to the control-point-free bundle adjustment, precise GNSS perspective centre coordinate computation will already solve this tasks for imaging blocks with several overlapping flight lines. The performance of such UAV-based image orientation and product generation without using any additional control points was analysed in a joint project together with the national mapping agency of Baden-Württemberg (LGL BW). The underlying application was the final survey of a re-designed rural road, which caused changes in the existing terrain. Final goad was the updating of the already available (laser-scanner based) DTM from multi-view stereo point clouds, derived from the UAV-images. Such image based dense point cloud generation using UAS platforms may offer an option to flexible map those changes almost immediately. With the use of directly measured GNSS (and/or GNSS/inertial) exterior orientations, such process might be solved very efficiently. More ...

Relative Orientation and Modified Piecewise Epipolar Resampling for High Resolution Satellite Images Relative Orientation and Modified Piecewise Epipolar Resampling for High Resolution Satellite Images

Nowadays, high resolution satellite image data have been commonly used for Digital Surface Model (DSM) generation and 3D reconstruction. Different to standard photogrametry, commercial satellite imagery vendors usually deliver Rational Polynomial Coefficients (RPCs) instead of ex- or interior elements to the customers. RPCs build a generalized and direct relationship between image and object coordinates. This relationship is pure mathematic and without any physical meanings. The qualities of the stereo image rectification and subsequent procedures are all depended on the accuracy of the RPCs. It is common that the RPCs’ precision is not accurate enough and it will cause bias between the calculated coordinates and the true location. Moreover, it is not easy to obtain ground control information to refine the RPCs for every dataset. Therefore, our work presents two relative orientation methods which use the corresponding image points only. More ...


For further information please contact Dr.-Ing. Michael Cramer.