Video: Scratch Surface from DEM; Use Surface from GIS!!


imageAn issue, I and other users have experienced when creating a surface from a Digital Elevation Model, or DEM, is the “grid like” appearance of the contours generated from the surface. This is because Civil 3D builds a DEM surface based of the grid elevations, in my case, a 30 meter square. This is not even an accurate surface for a preliminary natural ground surface.

imageWith the use of Map 3D functionality inside Civil 3D, you can connect to the DEM and generate a contour layer intern creating a SDF (Autodesk personal database file) then  MAPIMPORT to bring in the SDF data as AutoCAD objects. You can use the MAPEXPORT to export the object data as a SHP file that can be selected from Create Surface from GIS.

Hint: To do this successfully, maintain the DEM, source coordinate system when Connect to Data. When you use MAPIMPORT to re-import the SDF, set the coordinates to you project coordinate system! When you use MAPEXPORT, the new coordinate system will be applied so that your surface is created in the correct location.

Click to play...

The process only takes roughly five minutes to complete and you will end up with a better looking, more accurate surface to work with. Select the image to start the video…


Ryan Caudell

Total CAD Systems, Inc.


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