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Photogrammetrische Systeme

Forschungsaktivitäten und Projekte

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 ...

Efficient Engineer-Geodetic Monitoring of Traffic Structures Efficient Engineer-Geodetic Monitoring of Traffic Structures

The lock Hessigheim is located at Neckar 143.01 km and built on unstable ground. Natural underground chambers arise due to eluviation of gypsum in the anhydrite layer. For this reason, the ground submerges continuously. The relative submergence of ground is about 1 mm/a up to 1 cm/a (relative to direct surroundings). The corresponding relative translatory movement is in the range of several mm/a. Absolute submergence is unknown. However, from a monitoring point of view relative movement is sufficient.
We monitor the lock in collaboration with the Bundesanstalt für Gewässerkunde (BfG) and the Amt für Neckarausbau Heidelberg (ANH). More ...

On the potential of low-cost UAV camera systems On the potential of low-cost UAV camera systems

In former photogrammetry much effort was spent into the development of highly precise and stable camera systems, which are known since decades. Similar concepts have also been applied, when analog imaging moved into digital. With the advent of unmanned aircraft vehicles (UAV) this concept changed, mostly due to the limited maximum take-off-mass (MTOM) of those systems. Typically an MTOM within 10kg should not be exceeded. This in a way prevents the use of stable, but also heavier and bulkier systems. This is, why regular consumer grade cameras are used quite often. Alternatively, manufactures combine their UAV-platform with proprietary cameras, which are often optimized for taking video sequences. Still, such commercial and quite low-cost UAVs increasingly are used for photogrammetric surveys. As an example the dji products of the Phantom or Inspire series could be mentioned, which have been established to map 3D structures of limited size. The wide distribution of such platforms is due to their easy use and attractive price. Many users, like engineering offices, who now have extended their terrestrial survey portfolio by UAV-based mapping, have invested in dji UAVs. More ...


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