Combine DTMs to get lowest elevations of the two surfaces

Question

I would like to take two terrains and merge then so the resulting surface will be the lowest elevations of the two. Any ideas how to accomplish this? 
 
 Thanks!

Marcus Blake · Answer

I've filled an enhancement request in your behalf #982269 to add this ability within OpenRoads.

jpln · Answer

There is an easy workflow in OpenRoads using the Create terrain model from design meshes command. 
 Terrain 1 and 2 displayed alone in a DGN. Both with a feature definition where volume option is set to design Create terrain model from Design Meshes using option Bottom .