Our objective here is to obtain a GeoTIFF representation of topographical survey data.
The best source of data for any new entrant must be OpenTopography, which is an invaluable collection of topographical data from across the world. Your first step is to find the most appropriate (typically: highest resolution) scan available for your region of interest. This may be done via their map-based query tool. Make sure the survey you select completely encompasses your region of interest. We will discard data outside your region of interest when we download the data. Consider signing up for a free account at OpenTopography, as this will let you check on your export jobs easily. Once you find a suitable dataset, visit its detail page by clicking its name in the map popup that shows when you click on a survey. For this example, we can use a scan of the Flatirons area in Colorado, USA: https://portal.opentopography.org/datasetMetadata?otCollectionID=OT.032012.26913.1. Please always abide by the license listed on the dataset. For this example, the license is CC BY 4.0, but this is different per dataset.
You should be on a dataset info page that looks a little like this:
If you need an example page, you can use this scan. Click the "Raster Data" button as indicated by the red arrow in my screenshot. You will be dropped onto a fairly complex page, but we are almost done. Select GeoTiff as the Data Output Format, and make sure
Digital Terrain Model (DTM) is selected. If you want to include trees and buildings, you will want
Digital Surface Model (DSM). You can read about the difference here. Next, use the Select A Region button in the map (denoted by a red arrow in my screenshot) to select your region of interest (click and drag on the map after clicking the button):
Enter a meaningful-to-you job title and description at the bottom, double check your email, and leave everything else as default. Click
After a while, you should receive an email like this:
Go ahead and follow the link and download the file, then click on "Download compressed raster results".
Extract the single TIFF file in the downloaded archive and put it somewhere convenient.
For this we will use a project call
phstl to process the GEOTIFF into an STL surface, and then Meshmixer to make it into a printable solid.
Make sure python 3.X and git are installed (see above links). Then, the steps are:
pip3 install gdal # install the GDAL library, needed for phstl git clone https://github.com/petebachant/phstl.git # Get phstl cd phstl git checkout py3 # Switch to a branch that supports modern Python
Make a note of the full path to the
.tif file you extracted earlier (in this example we will use
/home/user/output_hh.tif) and invoke phstl:
python3 phstl.py /home/user/output_hh.tif /home/user/my_surface_terrain.stl
This will generate a file called
/home/user/my_surface_terrain.stl but this is not printable yet. For this we will need to follow
phstl's own tutorial using Meshmixer to extrude the surface into a flat-bottom surface. Make sure you follow the steps under "Extrude a Surface with a Flat Base". Once you have completed that, return to this document.
It is likely your mesh will be hundreds of megabytes to gigabytes in size. This may overwhelm your computer, so you might want to reduce the model's triangle count. You can use MeshLab for this (tutorial) or any other software you like. Make sure to re-export the model as STL when you're done. I personally skipped this step and let my computer work through the model for a few hours.
At this point we go into general 3d-printing territory which is beyond the scope of this article. My workflow is to use PrusaSlicer to hollow and support the extruded STL if I'm using a resin printer. You can find a guide here. Once supported and hollowed, I export the model with
File -> Export -> Export Plate as STL Including Supports and then slice and print with Photon Studio.
Of course, use any slicer suitable for your machine. Hollowing and supporting is not necessary for regular FDM (filament) printers, as slicers will do this automatically.
Load the final STL into your slicer and print it out. You can get a surprisingly good result even with 0.1mm layer hight, but go with a setting most appropriate to your machine. I used
0.02mm for my Anycubic Photon Mono X.
For painting the model (optional, though it's probably good to at least paint it a solid tan color for visibility), my process was:
Apply the tan color to peaks in a drybrush technique, as per this video:
It is OK if your first attempts don't look right. You may need to try the paint several times. Watch plenty of videos on YouTube about various model making techniques (keywords: drybrush, model washes, miniature painting) and you'll get it with time! It is OK to start over, just put a new coat of primer and tan base coat if things get too messed up.
Thanks for reading, and enjoy!