True Ortho

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.

Applications
  • Processing of aerial imagery – in particular large frame nadir imagery, but also oblique and UAV
  • Useful for mapping applications – perform feature extraction or overlay GIS data

Input and Output

Input dataDescription
DSM_ExtendedExtended DSMs created during DSM step
OrientationsInput camera orientations
ImagesInput images
colorAdjustment FileInput file that contains the color balancing parameters
Output dataDescription
Cloud_Refined

Interpolated cloud with new colors from Refined True Orthophoto

Ortho_RefinedTrue Orthophoto

Usage of the ModuleTrueOrtho.exe

True Ortho will be executed by default when you run the 2.5D workflow in SURE using the GUI or the CLI.

  • SURE GUI: Select the processing step of True Ortho in the GUI (if the Analysis was run with the current release, then the colorAdjustment File will be automatically read and applied on the True Ortho)
  • SURE CLI: 

    SURE.exe [...] -true_ortho -color_adjustment [...]   # True Ortho activated and the color balancing of the True Ortho will be executed through the -color_adjustment flag
    SURE.exe [...] -no_true_ortho # True Ortho deactivated
  • Standalone module:

    ModuleTrueOrtho.exe --dsm [...] --ori [...] --img [...] --controlfile [...] --output [...] --area [...] --color_adjustment [...]  # True Ortho with color balancing
    ModuleTrueOrtho.exe --dsm [...] --ori [...] --img [...] --controlfile [...] --no_color_adjustment --output [...] # True Ortho without color balancing
References