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.
For one reason or another drawings sometimes need to be moved from one coordinate system (datum) to another. A classic example may be moving from a NAD 27 datum to a NAD 83. Whatever the case may be, how might one perform this translation as accurately as possible?
To answer that I turn to good old Map 3D. As you may know both AutoCAD Land Desktop and AutoCAD Civil 3D are built on top of AutoCAD Map 3D, so if you have either product, you also have Map 3D. Users of Map 3D naturally know it’s power, whereas I have found many civil engineering professionals nearly forget about the Map menu altogether. While it may seem odd, we’re actually going to start the translation from a blank drawing.