True-Orthophoto for Hamburg City

In 2018, the Landesbetrieb Geoinformation und Vermessung (LGV) commissioned BSF Swissphoto to carry out a photo flight over the city of Hamburg to produce orthophotos with a resolution of 5 cm. The entire city area (800 km2) was flown. A special feature and novelty in this project was the large-scale calculation of a digital surface model (bDOM) as well as the generation of a TrueOrthophoto with the software SURE from nFrames.

The production of the True-DOP relies on a novel working process, which can be described in the individual steps: analysis, dense cloud calculation/ 3D point cloud creation, DSM creation (bDOM calculation) as well as the calculation of the actual TrueDOP. In the Dense-Cloud calculation process, the semi-global matching algorithm (SGM) is used to generate a compressing 3D point cloud in TIN from the aerial images. Each point in the point cloud has RGB values. A bDOM (DSM) is then processed from the 3D point cloud in a regular grid. The last step is the calculation of the final TrueDOP (SURE Ortho Refined).