I have been away from this tool for a couple of months but for some reason seem to have forgotten a workaround I had for importing a heightmap. I tried Brady's example in an earlier thread but an odd thing almost always happens. I tried creating the image in various tools and various formats. I've gone back to trying to use a geotiff. I've tried 8 bit, 16 bit and 32 bit. When the file is imported, it seems to put it in the correct place but the odd thing I encounter is that I never see the terrain. When I "fit" it in the scene, it goes to where I expect but there is no geometry. The grid position looks right but the perspective view contains 1 object, 0 polygons.
There was something I'd forgotten to do in my importing process but I can't for the life of me remember what it was that made all the difference.