Hi Anthony, The Ground Extraction tool works in 3 steps. 1) The value of the "Largest Infrastructure Size" setting is used to create a grid over the Reality Model (Reality Mesh or Point Cloud). The grid's tiles must be big enough that each tile contains at least one ground point. Ground points (called "Seed Points") are found in each tile and a TIN is computed from those points. To validate seed points, output them to a DGN level by selecting the "Seeds" output method. 2) The second step consists of iteratively refining the TIN created in the first step. The "Terrain Variation" setting influences the number of iterations. A smaller value will create a flatter terrain. Getting this setting right may require a bit of trial and error. 3) Once the TIN refinement is completed: -If the user has chosen to output a "Terrain", the Geopak .Tin file is created and an STM is automatically generated. -If the user has chosen to output a "Classified Point Cloud" then a threshold is used to classify all points of the point cloud that is within that distance from the TIN surface to the "Ground" class. (When the input is a Reality Mesh, a Point Cloud is automatically created and classified.) One last thing that can influence the result. When working with a reality mesh, the model’s resolution is determined by the Export Resolution setting. To change this setting: Select a reality mesh attachment. Open the "Properties" dialog. Navigate to the "Reality Mesh" section. Hope this helps. Don't hesitate to ask if you have more questions. Pascal
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