Merging Ground Elevation Maps

[tpwooton]

Is it possible to merge another HOG generated ground-elevation map within an existing session? Basically, I've reached the outer limits of the board I'm currently working on, and would like to continue my line into another area...

 

[cascaderailroad]

HOG DEM's are measured in meters abve sea level (being 0.00m).

One DEM might be 400m elevation, and another might be 200m elevation ... so a horseshoe or a series of S curve ramps on several baseboards might be needed to gain elevation, or a spiraling helix like on model railroads, or DEM's connected by Portals