Creating a 3d STL terrain model from usgs or google earth for CNC

I wish to capture a bit of US terrain like a lake and turn it a solid STL mesh I can import into my CNC program (Enroute) and carve it. I have been able to capture and grab an area but don’t know how to make it an STL solid mesh.

The model must be a “Solid Group” or “Solid Component” and then exported to STL
I. e. A closed volume.

Intersect a cube with the terrain and erase what you don’t need.
Here’s an illustration. Download the model and have a look.

Dear Geo,

I’m new to sketch and am having trouble trying to 3D print a front yard landscape. I have a contoured terrain (not flat), so I would very much like to make the volume below the contoured terrain a solid, with a flat bottom. I see you have essentially done that here in this thread, but when I tried it, I did not get a good result. I created a box, put my terrain through the center of it, and then hit “intersect faces”. This seemed to work, after I first went in to the box to make it a group (which seems to be what makes it a solid). I then went in with the select tool and selected the sides of the box above the terrain and hit delete. Seemed to delete them as I would like, but when I look inside the remainder of the box, it is no longer a solid and I dont know how to make it one. Can you help me? I attach the file here.C&J Model 2.skp (719.2 KB) Thank you in advance. Kindest regards, Mike

Hi Mike, @mpuyot

Here’s a reworked version of your model.
C&J Model 2 Fixed.skp (739.8 KB)

Therein, I made copies of the terrain & base and then cleaned them up a bit to create a Solid Group.
Examine the difference between what you’ve modeled and the way you must model to create a Solid.

Creating geometry in separate groups and/or nesting a group within a group as you’ve done, won’t work.
All the geometry must be within a single Group or Component.
Moreover, neatness counts when creating a Solid.
Just one stray edge or tiny gap will spoil the broth.

• The geometry must form a single* airtight vessel.
Like a soap bubble … •No gaps •No holes •No leaks

• No extraneous Faces inside or outside the vessel.
That is, all **Faces must serve to enclose the singular volume of the vessel.

• No stray Edges.
That is, all Edges must serve to support a Face that in turn serves to enclose the airtight vessel.
Said another way … Every edge of a Solid is bounded by two faces; no more, no less.

*A Solid Group or Solid Component may contain one or more separate airtight vessels.
**Best that all Faces are oriented Front Side (white) facing out.

Thank you Geo. I downloaded the model you made and it is exactly what I wanted to do. Trouble is I dont know how you did it (sorry for being dense - it’s my first model in Sketch, have watched the videos on essential training, but I am just not finding any training specific to creating a solid out of non-flat terrain).

Could you walk me through how you created the solid from a single vessel? I see you have the terrain shape I had and assume that is the one part of my model you used, but then you somehow extruded that into a solid. That is the piece I am missing.

Thanks again for your coaching - it is extremely helpful


Hi Geo,

One basic question - when I do a section view of the solid you created, the view seems to imply it’s not solid (by this I mean once I see through the outer face, I can see all the way to the far end of the “solid”). I expected at each section, I would still see a non-translucent surface, and could only see 'through to the end" if I turn on X-ray vision, which I dont have on. Can you help me understand this?

Kindest regards,


Despite calling certain objects “solids”, SketchUp is a surface modeler. Everything is actually a collection of infinitely thin Faces and Edges. A solid is a collection of Faces that is water-tight (no holes), and has no extraneous Faces or Edges not necessary to close the surface. A section cut is a display trick that causes OpenGL to omit displaying everything to one side of the cut, and so you can see the inside of a “solid”.

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The reason I ask is I intent to 3D print the ‘solid’. If in fact it is hollow, that will have implications on how well and fast the 3D Printer can actually print it. Will a “solid” in SketchUP end up as a solid as printed in a Makerbot? I assume the answer to this is yes. Thank you for the excellent clarifying points you make.

I’m not a 3D printing expert, but it is my impression that the exporters that create stl from a SketchUp model export a SketchUp solid as an stl solid. You may have to draw an inner object to give the skin a particular thickness to minimize printing time and materials. The software for the printer may also be able to make such adjustments.

Hello again,

I am starting to understand what you meant Geo…I have gone back and taken the model you fixed (thank you) and built up from that, but all geometry carefully built onto that solid such that I only have one solid. I see that I need to be much more careful to create a proper solid, as you pointed out. I still have not gone back to verify that I know how to create a solid from a terrain. That is the magic I was originally after, and I will play around with that one over the weekend. Thank you all for your help.

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Hi Geo, I’m so pleased to have found this topic, as I am trying to achieve a similar result. However, I am starting from a 3D TIN that I derived from an ESRI grid in 3D Analyst. I need to take the TIN in Sketchup, and convert it to a solid surface with a box-like skirt, as you did with your terrain in this thread. Can you advise me on how I can convert the TIN to a solid surface? Upon import, the TIN appears to be a wireframe only, as the triangular facets are not filled-in. When I use the “line” tool, if I re-trace each triangle, then they fill in, but there are tens of thousands of triangles so tracing manually is not an option. Any help would be much appreciated? Thanks.

You’ll find this plugin makes life easier.

MakeFaces v.1.400 by Todd Burch

Thank you for the reply. I am also wondering if there is a way to grab a larger area, I am trying to model Lake Tahoe and it will require hundreds of grabs and not practical.


Hi Gary

Given Lake Tahoe is some 22 miles long; modeling the lake and surrounding terrain would certainly prove problematic via the Add Location feature or whatever other means one might use.
SketchUp’s OpenGL rendering engine tends to have tantrums at such great distances.

Thanks Geo, any other ideas as to how to get large areas into STL format?