How do I carve a topographic map or terrain relief from real elevation data?

What the project is

You download a 3D terrain model, import it as a single component, then run a 3D Rough and a 3D Finish toolpath. The decisions that matter are vertical exaggeration, finishing tool size and stepover.

Steps

1. Get the model. The free TouchTerrain web tool exports an STL from a box you draw on a map. A detailed published workflow recommends the AW3D30 data set worldwide or USGS 3DEP 10 m in the continental US, the largest base thickness (5 mm), and binary STL.
2. Vertical exaggeration. Real terrain is very flat at map scale. That author uses about 3 times for a region 50 to 100 km across with modest mountains. You can correct it later in the software.
3. Job setup. Enter the measured stock size. Do not trust nominal plywood thickness.
4. Import. Use File, Import Component / 3D Model. Set Initial Orientation, click Center Model, and size it. To change relief height alone, uncheck Lock XYZ ratio and edit Z. Keep the model about a millimeter inside the stock, top and bottom.
5. Boundary. Draw or trace a vector around the model and use Selected Vector(s) as the Machining Limit Boundary for both toolpaths.
6. 3D Rough. End mill, 3D Raster strategy, Machining Allowance about 2 mm. The author avoids Z Level here because its square steps can knock thin peaks off.
7. 3D Finish. A small tapered ball nose (1.5 mm tip in the example) at 10% stepover. The official documentation gives 8 to 12% of tool diameter as typical. A larger tip is faster but blurs ridges.
8. Cut out with a Profile, or saw it free afterward.

Expect long run times

The example finishing pass ran over 8 hours on a large piece. A small 3.5 inch square student project took about 1.5 hours with a 1/4 inch end mill, a 1/8 inch ball nose and a 1/16 inch detail pass.

Pro tips

• Baltic birch plywood shows its glue lines as natural contour lines.
• If roughing removes the whole top surface, zero Z from the machine bed so you can re-zero after the bit change.
• See the entries on 3D roughing strategy and on speeding up 3D finishing.