Create a drainage analysis surface from USGS data in Civil 3D

Last updated: 2020-10-26

Total video time: 25:10

Exercise files: srfc-create-drn-anlysis-dem-data-C3D12.zip

srfc-create-drn-anlysis-dem-01.mp4 6:38

This segment will demonstrate how to download USGS DEM data.

Download USGS DEM data

  1. Open the USGS National Map Viewer http://viewer.nationalmap.gov

  2. Click the Download Data button at the top of the screen.

  3. Navigate to your location

  4. Turn on the Box/Point button and drag a rectangle around the area you wish to capture

  5. On the left check the Elevation Products (3DEP)
  6. Multiple options will likely be available to you. The smaller the arc second value, the higher the point grid density will be. Point elevation accuracy is the same. Check the desired data set. Be sure to choose the ArcGrid format.

  7. Click Find Products

  8. Click Add to cart. View cart Download

  9. It will take a few minutes to download
  10. Unzip the data to your project folder \BaseData\Other\USGS-DEM\
Info: Note: 1/3 arc second is typically adequate, but download the best available. Later, if you are unable to load a denser point density, try a larger (less dense point spacing) or break the DEM into smaller pieces. This may occur on larger areas.

srfc-create-drn-anlysis-dem-02.mp4 18:32

Warning: This segment includes a large dataset and may take a long time to download.

Create USGS DEM surface file

Create a new dwg file from the WisDOT template and save it as Surface-USGS-DEM_meters.dwg.

  1. In the drawing settings set the Drawing Units to Meters. Set the Zone to USA, Wisconsin and Wisconsin County Systems: {Your project County}, Meter. Click OK.
  2. Import the project mapping into the drawing to provide spatial reference. Refer to nosrvy-bsdata-wrk-sptl-rfrnc-DWG-img-GIS for this procedure.
  3. Draw a closed polyline around the area where the DEM Surface is needed. Make this area as small as possible to improve system performance.
  4. Create a new surface called USGS-DEM
  5. Expand the surface definition in the Toolspace-Prospector.
  6. Right click on Boundaries and select Add....
  7. Set the Type to Data Clip. Click OK and select the closed polyline from the screen.
  8. In the Toolspace-Prospector, right click on DEM Files under the surface definition. Select Add...
  9. At the top of the dialogue box, select the DEM file. The file extension is ESRI Binary Grid (*.adf). You will see multiple .adf files in the data set downloaded. Choose the one with the largest file size.
  10. Set the CS Code to Lat Longs, NAD83 datum, Latitude-Longitude; Degrees. (Coordinate System Code is LL83) Click OK. Civil 3D will transform the DEM surface from Lat/Long to the coordinate system assigned to the drawing. However, it will not transform the elevations. This is why we first bring the DEM into a metric drawing.
  11. Click OK to finish loading the DEM file. The surface is now viewable according to the assigned style. This may take some time depending on the point density and area.
  12. In the Toolspace-Prospector, right click on the surface and select Export LandXML... Make sure the surface (only the surface) is selected in the Export to LandXML dialogue box. Click OK. Save the xml file to the BaseData\Other\USGS-DEM\ directory. Name the file USGS-DEM_meters.
  13. Save and Close the drawing.
  14. Create a new dwg file from the WisDOT template and save it as Surface-USGS-DEM_USFoot.dwg.
  15. In the Drawing Settings, set the Zone to USA, Wisconsin, Wisconsin County Systems: {Your Project County}, US Foot. Click OK.
  16. Data shortcut reference your roadway alignment or xreference your mapping to provide spatial reference.
  17. From the Insert Tab - Import Panel, click LandXML. Select the USGS-DEM_meters.xml file and click Open.
  18. Click OK at the Import LandXML dialogue box. The DEM surface will now appear in your drawing according to its assigned style. Save the drawing and create a data shortcut for the surface. The DEM surface now has elevations in feet.