Here are some youtube links showing how I make my UE4 terrain maps from DEMS. I made these videos for my own reference as for in a couple months and my old age I will forget how I did some things. I have a lot of hillbilly slang and I have never made a tutorial before so please forgive me. 
I never pause the video so you get to see me struggle with some different problems I encounter. The videos ended up being alot longer than what I expected. The maps when complete do not end up photo realistic, but its a good foundation for maps that meant to be played as a FPS with vehicles, aircraft, and ground pounding. Also once you get the hang of it you can do large maps start to finish in about 20 minutes compared to weeks if you had to make the maps by hand. Also as I ask in the video if anybody knows of some tricks or better way please do tell.
Some snap shots show end result.
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The materials are default ones used in UE4 editor. One could do a better job.
And here are the youtube links on how I make these maps.
Part 1 DEM Real World Terrain Unreal 4 UE4 Landscape tutorial MicroDem TerreSculptor Part 1 - YouTube
Part 2 Unreal 4 Huge Terrain-Landscape from Digital Elevation Maps using MicroDem and TerreSculptor Part 2 - YouTube