True Orthophotos // Surface Models

The True Orthophoto (TDOP) is created on the basis of surface data in a fully automated process. The advantage of a TDOP is, outstanding objects, such as buildings are not oblique. So, the roof of a building is located directly above its ground plan, as seen in the right picture. There are no visible spaces.

The basis of a True Orthophoto is a arial photo flight with an increased overlap. In the case of a classic orthophoto, an overlap of 60 percent in the direction of flight and 30 percent across the direction of flight is sufficient. For a True Orthophoto, these overlaps must be doubled at least to 80 percent in the direction of flight and 60 per cent across the direction of flight. The orientation data for the stereo models are calculated using a highly accurate aerotriangulation. On the basis of these orientation data, heights are derived from the aerial image data using the semi-global matching algorithm. As a result of this process, a surface model is created. For well-defined points, e.g. roads or roofs, the height accuracy of the individual points is less than 10 cm. With the help of special software, a 3D view can be generated. Due to the geometric accuracies of the True Orthophotos, the use in technical surveys is much higher than in the use of normal orthophotos. To process the True Orthophotos and 3D meshes, the GeoFly uses the software "SURE" from the company nFrames. Together with the nFrames team, we are constantly working on optimizing the True Ortho process chain.


  • e.g. Disaster control
  • Cadastre
  • Topography capture
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