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.

0.0 File Preparation

There are other ways of obtaining 3D models online and once you do so, you can easily follow the 3D printing steps to generate your model.

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.

1.0 Cadmapper - Urban Terrain

Cadmapper is a web tool available and allows students to download up to 1 km for free.

https://cadmapper.com/

  1. Download desired size (more than 1 km requires you to purchase the model)

  2. Save output format and open in Rhino

1.1 How to create the Base

Figure 1.1.1 - Draw desired Base Model Size
Figure 1.1.2 - Extrude Curve
Figure 1.1.3 - Trim Curve with Topography Mesh, Cap and Join

2.0 Terrain2STL - Terrain Models

Models can be found (without buildings) free from: http://jthatch.com/Terrain2STL/

  1. Location > Center To View (Red Box)

  2. Adjust box size using slider ( Larger sizes will result in bigger files )

  3. Vertical Scaling is to increase height of terrain (result of map will be inaccurate)

Figure 2.1 - Terrain2STL Tools

2.1 Exported Terrain

Exported terrain can be imported into Rhino.

2.1 Issues and limitations

The exported mesh will be problematic as it is an open mesh. A option is to upload the file to Netfabb to try and fix the open meshes.

Figure 2.1.1 - ShowEdges

3.0 Printing Topography using Grasshopper

3.1 Plugins

This tutorial uses Elk version 0.3.1. You can download the latest version of the Elk plugin for grasshopper.

3.2 Datasets

Elk can use a variety of datasets which are all derived from the Shuttle Radar Topography Mission.

3.2.1 .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 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.

Figure 3.2.1.1 - OSM > Export > Manually Select a Different Area, to grab your desired range.

Referring to this coordinate range, download the corresponding range from the .hgt data portal.

Figure 3.2.1.2 - Open Street Maps and the hgt portal

South/West co-ordinates are (-)Negative, North/East co-ordinates are (+)Positive

3.2.2 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.

3.3 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.