DEM and breakline export for use in CAD software

When generating a DEM in LP360 / True View Evo for import into CAD software, there are a few nuances to consider. Unlike the commonly used LandXML CAD surface format, the DEM format will only enforce breaklines at the resolution of the generated raster. In order to properly enforce and display the breakline areas, you must also import the breakline feature used during DEM creation/export. Below we’ll review the proper workflow for importing a DEM with breaklines into CAD software:

Initial processing and preparation

  • Classify ground – Classify the ground surface for the desired DEM export area.
  • Define breakline areas – For the areas that require breakline enforcement, create or import breaklines in the LP360 project. Feature edit tools can be used to create or edit these features.
  • Buffer breaklines – Once you have the desired breaklines, classify a buffered area around the breaklines.

Export settings

Select export settings that properly define ground source points and breaklines to be enforced for DEM creation:

  • Source points – Classified ground surface – Class 2
  • Surface method – Must be TIN to properly enforce breaklines
  • Cell edge length – Choose the desired DEM pixel size. Ensure that this is adequate for the project being produced.
  • Breakline enforcement – Ensure that all relevant breakline features are chosen for enforcement on export.
  • Raster format – Choose the desired raster format

Additional steps are used to define the extent and output location of the DEM.

CAD import considerations

Now that the DEM and breaklines are created, the user can import these into a CAD package. A few final details to consider:

  • The DEM and breaklines must both be imported into the CAD software to properly reflect the surface.
  • The SRS must match for both the DEM and breakline feature(s).
  • In Civil3D, the user will possibly have to alter additional settings, depending on the units and coordinate system used.
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