While importing surface data from Google Earth is probably the easiest way to get some conceptual topographical data into your drawings, DEM’s have to be a close second. For the uninitiated, DEM’s or Digital Elevation Models could be described as a surface whose data is organized in a grid. This is fundamentally different than DTM’s (standard Civil 3D surface) which still stores a collection of points, but in the form of triangles not a structured grid. The great thing about DEM’s is they’re readily available for FREE from a wonderful website named the Geo Community. Now don’t be fooled when you visit the site as you will see all sorts of premium content; never fear as there’s ample data that can be had for free!
One of my users called me the other day asking if there was any way to convert our DTM surface into a DEM surface, as a client had called them asking if it was possible. The short answer to the question was yes, but let me review the fundamental differences in these formats before getting into the how-to of this task. Both formats exist for the same fundamental reason – to capture a representation of the earth’s surface. What differs is the way each stores that data.