Create a surface from CAD contour data in Civil 3D

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Creating a surface from CAD contour data is used when converting elevated 2D contour data to an intelligent surface.

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For this functionality to work, the contour data needs to have elevation data assigned to it.

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To check if elevation data is assigned, select any contour or polyline, then right-click it and select Properties.

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Under Geometry, if the Elevation displayed is not zero, then elevation data is assigned.

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To convert these polylines to a triangulated irregular network, or TIN surface,

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from the Home or View menu, in the Palettes panel, click Toolspace.

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Click to display the Prospector tab.

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Right-click Surfaces and select Create Surface.

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In the Create Surface dialog, enter the following for this example:

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Type: Triangulation (TIN) surface

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Name: NGL

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Description: Natural Ground Level

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Style: Contours 2m and 10m (Background)

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Click OK.

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Back in the Prospector tab, expand Surfaces and click to expand the surface name—in this case, NGL.

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Then, expand Definition, right-click Contours, and select Add.

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In the Add Contour Data dialog, you can add a description,

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adjust the weeding and supplementing factors, and toggle options to minimize flat areas.

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Weeding reduces the number of points generated along the contours,

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whereas supplementing factors add vertices along contours.

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Click OK.

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The command line prompts you to select the contour data.

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Select all contour data by selecting the objects with elevation, and then press ENTER.

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The CAD contour data is now converted to a TIN surface.