Oops, .DEM file typo.

Your looking for what's called a digital elevation model or .DDR file. They come in several resolutions the highest being 1meter or one data point per one meter of aerial scan. Back when I gave this a go I used a free program called Acutrans for the conversion. Rhino to visually scale down the z axis (came thru way out of scale, but only in the z, idk...) Then exported into deskproto for milling as mc9 wouldn't take in meshes yet. Hope this helps some, good luck.

1/4 compression mills were typically my weapons of choice. They run at higher feeds, provide hold down force and leave perfect top and bottom edges on laminated plywoods. Just remember to always ramp in a compression tool or down spiral to eject cuttings and extend tool life. Depending on vacuum and machine rigidly 500ipm should be achievable all day.