HT2 - Create a Digital Terrain Model from a T-Lidar point cloud

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This tutorial uses the following script in the Computree HowTo subfolder: HT2_Create_DTM.xsct2


This tutorial shows how to :

  1. Open a point cloud
  2. Add the DTM creation step
  3. Configure the tool parameters
  4. Export the model in a raster format

Open a ploint cloud

Please refer to tutorial HT1 - Load, visualize, crop and export a T-Lidar point cloud.

Add the DTM creation step

The OE_StepExtractSoil03 step is found in the onfensamv2 plugin. This step distinguishes ground points from vegetation points and generates:
  • a Digital Terrain Model (DTM)
  • a Digital Surface Model (DSM)
  • a Digital Height Model (DHM)

To add a step, right click on the previous one and then select the tool. Select the onfensamv2 plugin, and then the Soil / vegetation segmentation → DTM step.

Tool parameters configuration

Tool steps and parameters:

  • A Zmin grid is created at the specified Grid resolution. The resolution must be in centimeters. The same resolution will be used for the output models.
A 50 cm resolution is suitable for a moderate slope plot. For a steeper slope, a finer resolution is recommended.
  • Point density is calculated for points located between Zmin and “Zmin + Soil thickness”.
The Soil thickness parameter depends on the grid resolution. The larger the pixels are, the greater the parameter value must be, so that all ground points are included.
  • NULL value is given to the grid’s pixels that have a point density smaller than the Minimum density.
  • If the Interpolation box is checked, NULL values ares replaced by the average of natural neighbors.
  • If the Smoothing box is checked, each cell is transformed according to the K-Nearest Neighbor (k-NN) method. K (Neighborhood in number of pixels) must be specified.

Here is an exemple of a Digital terrain Model (DTM):

Export the model in a raster format

Please refer to tutorial HT1 - Load, visualize, crop and export a T-Lidar point cloud.

The Grilles 2D, ASCII ESRI Grid format is recommended.

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