Terrain scan of a leaf covered forest area processed in PhotoScan and tiled using Substance designer 6 new nodes.
The scan area is around 2 meters wide and about 1.5 meter tall. From this I baked square section about 1.5 meter in size for the starting Base,Normal,Height, and AO maps.
Mesh generation in Photoscan was just under 10m polys and done using "height field" which was much faster than "arbitrary" projection.