Recommended Settings for Generating a True Orthophoto

The settings that are applicable to nearly all orthophoto projects can be set using the Enhanced True Orthophoto preset. This preset uses alternative 3D correlation focusing on horizontal surfaces to improve the representation of vertical structures and complex geometries. It is also recommended for Digital Surface Models (DSM) production.

Other settings vary depending on the project content, e.g., are there control points, or are there nadir and oblique photos. These should be set in the Build Parameters tabs, according to the recommendations outlined below. These settings aim to enhance the quality of orthos by minimizing the impact of noisy façade points. This is achieved by focusing on processing points with primarily vertical-facing normals (i.e., horizontal surfaces up to about a 60-degree angle) and extruding all other points from the roofline or any above-ground object down to the ground surface. The result is a cleaner, more orthogonal view, with sharper geometry.

To optimize True Ortho generation:

1. When starting the build, select this preset (Build Parameters > Presets> Select and Manage).
    
2. On the Build Settings tab, do the following:
   
   
   1. Under the Orthophoto Output, set Texture Blending to Yes, to best address moving objects in the final ortho texture. For datasets that combine photos from different days or times, resulting in significant shadow variability, the Extra setting is recommended.  To avoid any texture blending in final output, set Texture Blending to No. 
   2. In Bands and Collections > Click the three dots > On the Collections tab, select only the nadir collections, and click OK.
3. On the Presets tab, click Select and Manage > Select Presets tab: For best photo quality, use the True Ortho preset together with the "DataPrep: Set SMPT quality to JPEG 98%" preset. To apply local histogram adjustment to the photos on import, use together with the "DataPrep: Local brightness histogram correction for images (CLAHE) preset", which uses a CLAHE limit of 2. For gentler histogram adjustments, use the following AT flags in the Aerotriangulation tab, with a CLAHE limit of 1: @featuredetect2[ClaheClipLimit=1]
   
      
4. In the Build Parameters dialog, on the Reconstruction tab, do the following:
    
   
   1. Set Min. number of matches as follows: 3 is recommended for best results, and should be applied in cases where image overlap is sufficient (at least 70% forward and 50% side). Default is set to Auto for addressing cases with lower image overlap (60% forward, 40% side).
   2. In the Bands and Collections section > Use for point cloud and model, click the three dots  
   3. Then click the Collections tab and select only the nadir collections, and click OK.
   4. If your dataset has a NIR band, on the Bands tab in the same dialog, include the NIR band, to help in distinguishing between trees and buildings. 
   5. In the Texture section: In cases of images with graininess or noise, it is recommended to use lower Sharpening settings. If images are relatively clean, sharpening can be applied to enhance visual edges in the output.