Our TouchTerrain web application creates 3D terrain model files that can be printed on a 3D printer. You select the area you want to print, decide which Digital Elevation Model (DEM) you want to use, set some print parameters and let the app do all the work. When it's done, you download the 3D model file(s) (STL or OBJ format) and print it out on your 3D printer or send it to an online 3D print service.
Area selection (hillshade):
3D printed model:
This app is developed by Chris Harding and Franek Hasiuk of the Geofab lab at Iowa State University. It's use is free of charge but please understand that it is still in early development and so may not always work perfectly.
Let's say you want to 3D printable terrain file(s) for a certain area. First, you need to find this area on the Google Map.
The hillshade layer shows topographic relief, which tends to bring out ridges, river beds, and other terrain morphologies. It's useful for finding interesting terrain features for printing. The hillshade layer overlays the Google Map (street map or satellite map); Move the Transparency (%) slider to "mix" both layers, the higher the % the more the Google basemap will come through:
70%, with street map
You can further tweak the appearance of the hillshade layer by setting different Gamma Correction values, which affects the luminance of the hillshade. Low Gamma (< 1.0) values make for a generally darker hillshade but can be helpful to bring out minute details, especially in relatively flat terrain. Unlike with the Transparency slider, where change is instantaneous, you have to click on Set New Gamma Value to see the change (because it requires server-side processing).
TouchTerrain offers several types of Digital Elevation Data (DEM) rasters, which differ in resolution and area coverage. Resolution refers to the real-world size of each raster cell (pixel), e.g. in the USGS/NED DEM raster, each cell is approximately 10 x 10 m. However, NED only covers the US - areas outside the US are covered at lower resolutions. After selecting a different Elevation data source, the areas covered by it will be shown via the grey hillshade layer:
~30 m resolution,
Worldwide up to 60 degrees latitude
~90 m resolution,
~1 km resolution,
Worldwide - including offshore (bathymetry)
Once you've decided on a general area, click on Re-center box in current view. This will show a red Area Selection Box, outlining the area you will 3D print.
This configures how the selected area will be converted into 3D model files for later printing.
It is useful to understand how these four parameters are linked to create good quality 3D models. You probably want your 3D printer models to show as much detail as possible, which means setting the parameters in a way that the re-scaled resolution is close to, but not lower, than the source DEM resolution. As this can be a bit of a juggling act, here's an example scenario:
Let's assume you want to create a tiled model with the SRTM GL1 DEM source, for which each cell is 30 x 30 m. With 4 tiles, each 8 x 6.5 cm and a resolution of 0.5 mm, the 30 m cells need to be rescaled (resampled, interpolated) to a 61 m cells for 3D printing. This means that as the 3D printer moves in 0.5 mm steps, it jumps (roughly) 60 m in reality, so the printed model would have less detail than it could, given the original DEM data resolution of 30 m. That's not necessarily a bad thing, you're just not getting the degree of terrain details that the original DEM sources data provides.
If you wanted to get a print with better detail, there are several parameters you could tweak:
By now you can probably see how these parameters interact. You could, of course, change multiple parameters at once, e.g. set larger tiles (12 x 9.8 cm) and use a finer 3D print resolution of 0.25 mm:
This results in a rescaling from 30 m to 20 m, which will print but is actually somewhat pointless. Resampling the original DEM resolution to 20 meters will not increase the information content, and you're unlikely to print a model with better details than using around 30 m. You will, however, wait a bit longer and get larger files, which is simply inefficient. In other words, you might as well try slightly coarser print resolutions (0.3, 0.35, etc.) until the rescale meter number is pretty close to 30 m.
However, depending where your area is located, you may have the option to switch to a higher resolution DEM source! For this area, we can switch to the 10 m USGS NED DEM data source, which, with the same settings rescales from 10 m to 20 m, which will in fact result in a truly more detailed printout.
To recap: Once you've selected your area you need to have some idea about the effective range of resolution your 3D printer can do (e.g. 0.5 mm is a bit coarse, 0.2 mm is very fine) and know the size of your build plate (e.g. you are limited to models less than 12 x 12 cm). Decide on a rough physical size of your final 3D printed map (i.e. all tiles put together should be about 40 x 40 cm). Set the number of tiles and the tile size and adjust the 3D printer resolution setting until it is around the original DEM resolution but not much below. To be clear, there's nothing wrong with ending up with considerably larger numbers, as in my 10 m => 20.33 m example from before, as long as you're happy with the total size of your final 3D printed map and the number of tiles you have to print.
Before you start to print it's advisable to check the 3D models first. http://www.viewstl.com/ is a web site for uploading and previewing each tile. It also connects you to Treatstock, which will show a couple of online 3D print services.
If you want to print yourself, your 3D print program (e.g. MakerWare desktop) will give you a 3D view of your model. Note that you should never need to scale-to-fit as each tile model already has a true mm-based size given by width, height and z-scale from the 3D printer options.
If you want to preview how multiple tiles look when put together, add them one by one to MakerWare desktop but do NOT have them move to the center. The x/y coordinates of all tiles are set so that all tiles will naturally fit together! However, the tiles will very likely exceed your build plate size, which is OK as this is just a preview.
Here are the four ETOPO1 STL files downloaded earlier, shown in 2 different colors to prove they are separate models:
(TODO: list of other multi-stl file viewers)
Looking at the 3D models, you may find that you don't like something in the model, e.g. you want more or less z-scaling or a different tile configuration, etc. Simply click the Back button on your browser twice and you're back at the Map screen with the exactly the same values you had before you clicked Export. Changes things to your liking and try again.
Restart MakeBot and add a single tile. This time, make sure it is put at the center of the build plate.