3D Printing Geography

When I set about this I wanted to 3D print a model of a golf course for a friend. "How hard could this be?" I thought. Turns out... harder than I expected. This post walks through the entirety of what I tried through the process. If you want you can skip to the end where I walk you through the steps I followed to make my final print.

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The first step is getting the tools for the job. So of course I did a lot of searching to find out what other people had done. I found this Reddit post which suggested using Equator to do the job. Despite putting in my credit card number for a free trial - I couldn't get it to work. (Maybe it was because something was broken and it was in the end of year holiday period.) 

Then, I found this post on medium that led me down a number of paths - only one of which I ended up taking in the long run! It suggested using OpenTopography to get the data, LASTools to convert the LIDAR data into a digital elevation model (DEM), and then QGIS to convert the DEM into an .STL for printing.

So first I go to OpenTopography, which provides freely accessible datasets, but... some of them are restricted for educational use only. You need a .edu email address, and I don't have one. So I continue searching. 

There are plenty of other locations for this data, and the good news if you are in the US, is that the US Geological Survey has the USGS Lidar Explorer which allows you to find where Lidar coverage is, and actually download the data. You can draw a box around your area of interest (AOI) and it will give you data to download for it. 

Now with data in hand, I ran the las2dem tool from LASTools against my dataset. And while I was able to get it to run, I got this warning:

WARNING: unlicensed. over 1.5 million points. inserting black diagonal.

Sure enough, LASTools was able to convert the data into a DEM, but it also made lines across the print which certainly reduced its realism. I fired off an email to the LASTools makers to see if they had any licensing for hobbyist use, but kept moving forward.

So, then I get QGIS installed - which is a free GIS swiss army knife of tools. Spoiler alert, QGIS is where I ended up doing all of the work in the long run. I could drag my DEM into QGIS and see it, generate a "hillshade" which makes it a little easier to visualize, but then also install the plugin called "DEMto3D" which allows you to convert the DEM into an .STL file for 3D printing. I found this terrific video on youtube that walks you through the process of using this plug-in, and I fully recommend you watch the video.

So, I'm through the process - generated a .STL, and printed it, and... was totally underwhelmed. The diagonal line is distracting, the trees are too pointy, the shape is laying at an awkward angle on a base that is square, there is a lot of stuff in the print I don't want... it's just not awesome.  

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But that's why we keep trying things and learning. So now let's get on with the ACTUAL process I followed for the final product:

• Use the USGS Lidar Explorer to download all of the original LIDAR scans that covered my AOI
• Import all the LIDAR data into QGIS (it aligned them together since the GPS information for the location was built into each file). In QGIS' advanced processing menu, in the Point cloud data management section, used the merge tool to pull the 6 files covering my area into one single dataset.
• In QGIS, rotate the maps so that you get your AOI as rectangular as possible to minimize wasted space.
• In QGIS, create a new Shapefile layer and draw yourself a polygon (ideally rectangle) around your AOI. Make sure to toggle editing of your shapefile off and save the file before continuing.
• In QGIS' advanced processing menu, in the Point cloud data management section, used the Clip tool to clip my merged dataset down to just my AOI.
• In QGIS advanced processing menu, in the Point cloud conversion section, used the Export to raster feature. This did what las2dem did without the ugly diagonal lines. The "with triangulation" mode seems to get higher resolution but that wasn't actually helpful for my 3d print.
• Use QGIS DEMto3D plugin to generate the .STL files. (I ended up using the tiling feature to do a large print. You enter the size of the final object, and the tiling will split that object for you.) Note that I found that adjusting the vertical exaggeration last was best using this plugin. I ended up doing 1.3x exaggeration for my golf course print.
• Print! I ended up doing standard resolution and printing took a long time and a lot of filament! 10-15% infill is plenty.