I knew I needed to make the map myself, because all the topo-maps you usually see have shaded hillsides to simluate depth, as if there is a light-source. That wouldn’t work properly for this this purpose, what we need for the topography to be accurate is a heightmap, where the lowest elevations are dark values and the higher elevations are light values.
I used Maperitive (free, open-source I think) to create the “Hypsometric Color Ramps” using just greyscale colors. I had never used Maperative before, and it was a pretty arduous forum-crawl to make it do the things I wanted. Everything about it was foreign language to me, so if I can do you, anyone can. This is what I came up with:
I knew I wanted the stand-offs to be embedded in the wood a bit, so that’s why you see those circles in the image.
Because of the elevations in Oregon, I think I set white to be about 1600’, because some of the state doesn’t have enough contrast at those high elevations, and I wanted some “stepping” effects to accentuate the changes. I also did a little bit of “posterizing” in photoshop for the same reason, though if I were doing a larger engrave (assuming the GF can handle it someday) I wouldn’t.
Finally, I’m too embarrassed to say how many times I’ve printed the image to try and get the values to translate nicely. I was determined to keep the heightmap “accurate”, but I did to a fair bit of value level adjustments between iterations.