Autodesk CIVIL3D - CIVILDESIGNCOMP 2007 SLM CD User Manual page 17

Contours
Contour data in the form of 2D polylines can be added to your surface.
Weeding factors can help you skip over extra, unnecessary vertices when the data is added to the surface.
While supplementing factors will allow you to sample extra points off long contours with minimal vertices.
Since by its nature, contour data tends to create flat triangles that do not accurately reflect the surface, there
are several options to minimize those flat triangles.
DEM Files
DEM files (Digital Elevation Models) are grid based surfaces. This is a format that is used by many different
Civil, Survey, and GIS programs.
DEM files are a format that is commonly used by the USGS and there is a
tremendous amount of data that is available online for free in this format.
Drawing Objects
AutoCAD object that have elevations can be used to build a surface. These objects include:
• Points
• Lines
• Blocks
• Text
• 3D Faces
• Polyface
Lesson: Building Surfaces from Survey Data
Chapter: Building a Survey Quality Surface
159