Topography Models
Topography models are now easily accessible and this guideline shows the different ways to obtain and set up a model for 3D printing.
Introduction
A topography model is a potential candidate to be 3D printed. In this section, we will introduce two methods for preparing a 3D topography model: one with Rhino and one with Grasshopper. Note that both methods will require additional resources and other services that are also covered.
3D Printing may not be the most cost-effective or time-effective fabrication method for creating topography models. Students should also consider Laser Cutting a contour model or using the CNC Router at the FabLab.
Preparing 3D Topography Model File - Rhino
There are several online resources - free and paid - that you can access to get a 3D model of your topography. Here, we list a few possible options.
Cadmapper - Urban Terrain
Cadmapper is a web tool available and allows students to download up to 1 km for free.
Download desired size (more than 1 km requires you to purchase the model)
Save output format and open in Rhino
You can then open the file in Rhino and build up a topography section.
Terrain2STL - Terrain Models
Models can be found (without buildings) free from: http://jthatch.com/Terrain2STL/
Location > Center To View(Red Box)Adjust box size using slider ( Larger sizes will result in bigger files )
Vertical Scaling is to increase height of terrain (result of map will be inaccurate)
Preparing 3D Topography Model - Grasshopper
Plugins
This tutorial uses Elk version 0.3.1. You can download the latest version of the Elk plugin for grasshopper.
Datasets
Elk can use a variety of datasets which are all derived from the Shuttle Radar Topography Mission.
.HGT Data
This is the most basic and accessible and open version of the data and will be used for the rest of this tutorial. The data can be accessed through this data portal:
For worldwide maps: https://dds.cr.usgs.gov/srtm/version2_1/SRTM3/
For US maps (higher resolution): https://dds.cr.usgs.gov/srtm/version2_1/SRTM1/
Refer to a mapping service that can give you a latitude/longitude range. OpenStreetMap (depicted below) is one such option to reference a range.
Referring to this coordinate range, download the corresponding range from the .hgt data portal.
South/West co-ordinates are (-)Negative, North/East co-ordinates are (+)Positive
Alternative Datasets
High resolution files .IMG are available for the US using the USGS TNM Download portal.
.GEOTIFF files are available from the Earth Explorer portal.
Grasshopper
In Grasshopper, load the file in using a File Path parameter by right-clicking the parameter and selecting Set One File Path. Navigate to the file's location and open it.
Plug the File Path parameter into Elk's SRTMTopo component.
Reference the Latitude and Longitude range of interest using a Construct Domain Component. In this example the OpenStreetMap data from before is used.
Right-Click on the [S] of the [SRTMTopo] Component and click [Bake] to export the surface geometry into rhino.
In Rhino, extrude the surface [ExtrudeSrf] thicken the surface and trim the base into a flat one for 3d printing using one of the many boolean operations.
The geometry is now ready to be meshed as per the 3d Printing Guidelines. Check out the following link for further reading on preparing the topography through Elk.
Issues and limitations
In most cases, the exported mesh will be problematic (usually an open mesh). An option is to upload the file to NetFabb Online Service to try and fix the open meshes.
Do not forget that in Rhino, you can use the [ShowEdges] command to check if the mesh is good or bad.
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