This tutorial is designed to direct possible approaches to creating 3D Prints based off of Lidar datasets. Methodology and recommendations come from personal experience creating a 3D print the University of Minnesota Twin Cities Campus.
Figure 1: Finished 3D Print of UofM Campus
Tools and Software used in this tutorial
Methodology
Step 1: Retrieve Lidar Data
Step 2: Process Lidar Data
Step 3: Create a DSM
Step 4: Export the DSM into a .STL
Step 5: Process for 3D Printing
Step 6: 3D Print!
Step 1: Retrieving Lidar data
I got my Lidar data from MnTopo, it's very straightforward to use and has data for the entire state of Minnesota. However, for the scale and amount of detail I wanted for my project, I needed at least a 8 points per square meter for the Lidar dataset, which is only available for the Twin cities region of the state.
MnTopo also has DEMs (Digital Elevation Models) available with the raw LAS (Lidar Datasets), however the DEM excludes buildings and only included the elevation of the landmass. Since I wanted to display the buildings of the University of Minnesota Campus I downloaded the raw LAS files so I could create my own DSM (Digital Surface Model).
Its also important to note that the LAS files come downloaded in a LAZ format (a compressed version of LAS files). LAZs require additional processing before they can be opened in most GIS Software packages.
You are welcome to get your Lidar data from any provider available to you, but keep in mind the level of resolution needed for your project goals, and the format they come to you in.
Step 2: Process Lidar Data
Processing .LAZ files requires the use of LAS Tools. It’s not the most user friendly software package, but it is freely available and we only need it minimally to process our Lidar data. The 3 main tool sets we need to make use of is las2las, lasview and las2dem.
Las2las helps us convert our .LAZ files into GIS compatible LAS files.
Lasview helps us get an initial (albeit not very detailed) view of what our Lidar dataset looks like, this isn’t necessary for the entirety of the project, but a good idea to check out to review your data before you get too much further in case there are any problems.
Las2dem is the tool that will help you get a head start on step 3 to create a DSM (I recommend making one for comparisons sake, it’s always nice to have options).
Step 3: Create a DSM
There are multiple options for going about this step. As I mentioned above, you can use LAS Tools to complete this step, but you could also use other software packages such as ArcGIS Desktop, 3DEM and Quick Terrain Modeler. Which software package you use may be dependent on which types you have access to. Additionally, each software package will produce a different DSM, so I recommend trying a couple if possible so you can compare model quality.
3DEM is a free software package with a limited toolset but works just fine for this project, especially if other more expensive software types are not available. It is very easy to use and doesn’t have a lot of extra gimmicks in the software, but it is retired and can be a little dated. However, keep in mind that 3DEM only takes the first returns of the Lidar Dataset (thus losing some of the detail) and does not interpolate over large portions of the dataset. For example, in my dataset, the Mississippi River divides the East and West Bank of campus, in the DSM created in 3DEM there is a “hole” in the dataset where the river is located, and would have to be edited in later steps.
Figure 2: DSM created using 3DEM Tool
ArcGIS Desktop is the most commonly used software package for GIS Professionals, and is also expensive to purchase if access is not readily available. While ArcGIS Desktop is capable of handling lidar, I would only recommend using it if you have previous background in ArcGIS desktop and comfortable with your skills. ArcGIS, while a powerful GIS tool, is weak at processing large lidar datasets and will take longer to convert the LAS files into LAS datasets (an esri specific database for Lidar in ArcGIS). However, the DSM that is extracted using ArcGIS will be fully interpolated and will not have any holes in it, even though it still only uses the first returns of the Lidar Dataset.
Figure 3: DSM created using ArcGIS Desktop
Quick Terrain Modeler would be my highest recommendation for creating a DSM if available. Quick Terrain Modeler was designed as a software package to be able to handle large datasets, especially Lidar. It takes into account multiple returns so that the DSM model derived from your lidar data, thus keeping a lot of the detail that Lidar is known for. However, it is very expensive software to acquire and I would not recommend purchasing it for this project alone.
Figure 4: DSM created using Quick Terrain Modeler
Step 4: Export DSM into a .STL
Once we have a surface model we need to convert it into a file that can be easily 3D printed. The way I would recommend doing this is creating an .STL file using a QGIS plugin. QGIS is the leading open source gis software and has a wide range of tools available in the form of plugins.
The plugin needed for this project is called DEM to 3D Printing. It’s a simple gui to convert the DSM into a .STL file however, the conversion settings are something that will have to be explored via trial and error in order to figure out what is right for your dataset. In order to visualize the differences between the different settings you will have to open the .STL file into a software designed for 3D Printing.
Step 5: Process for 3D Printing
Depending on your background editing 3D Models for 3D printing, different softwares are freely available to you.
If you are new to 3D printing and are still learning how to work with 3D models I would recommend opening and editing your .STL file in TinkerCAD. It’s very user friendly and can visualize our project pretty well. The only limit on TinkerCAD is the importing file size at 25MB maximum. While for most 3D datasets this is a hard limit to reach, Lidar datasets (and DSMs created from Lidar) can be rather large. The best way to work with this size limit is sectioning off your data into different sections so that the file sizes are smaller for importing into AutoCAD. In my project I ended up splitting the University of Minnesota Campus into 8 sections.
If you have extensive background in 3D printing and knowledge on how to use Blender, I would recommend you go about preparing your your 3D model using Blender, if only for the lack of a file size limit, which will help you evaluate your .STL settings more efficiently and be able to open .STL files with large amounts of detail from the Lidar.
Step 6: 3D Print!
How you go about 3D printing your model is dependent upon the 3D printer you have available. In my model I used a MakerBot Replicator+ with PLS biodegradable plastic. I ended up using the split sections to print each individually as a separate model in order to make a larger model size with a greater amount of detail. Each model took about 3-4 hours to print and each model had about 60-80 layers of plastic printed.
Want to 3D print my model?
Questions? You are welcome to contact me at barne703@umn.edu
