This tutorial will guide you through the process of importing topographic data into Rhino using RhinoTerrain. (In order to do this you will need the RhinoTerrain plugin installed. It is on some, but not all CRON machines, please contact CRON with questions on accessing the RhinoTerrain plugin.)
2. Now, switch programs and go to Google Earth. Navigate to where you want your topography to come from. Zoom in or out and center your window on your chosen terrain. Now, return to Rhino and in the window that opened up, click Extract. Once we update the RhinoTerrain plugin to a version that can handle Google Earth version 5 and higher, you will be able to change the Elevation Sampling to get a higher resolution topography. For the moment you will have to work with a 70 x 70 grid. (One thing you can do to get a higher resolution topography is to import multiple times from Google Earth, moving around your terrain. The only problem with this is that you will have to close Google Earth after every import, since RhinoTerrain will only import 5,000 points per “session”. However, if you save your location on Google Earth, this might not be such a big problem.)
1. First, you need to open Rhino and click on RhinoTerrain, Point Cloud, Import, Google. Once you click there, you will notice that Google Earth opens automatically, and that you get a message saying that since we have a Google Earth version that is above 4.2, you will only be able to import 5,000 points. (Hopefully, we will get an updated version of RhinoTerrain that solves this problem). Say OK once.
3. Once the importing is done, you will see the topography point cloud in Rhino. You can use this point cloud as it is or you can convert it to a mesh. The good thing about meshes is that you can analyze them and create contour lines really easily. To do this, select the point cloud and click RhinoTerrain, Terrain, Create, Triangulated Mesh. Once you do this, your point cloud will become a mesh and a few options will come up. Make sure you click Accept, otherwise you won’t complete the operation. Once this is done, if you switch to Rendered View mode you will be able to see more clearly the mesh you created.
4. To analyze the mesh, you can click RhinoTerrain, Terrain, Analyze, Shade, and select the mesh. This will color the mesh with a gradient representing elevation.
5. To create contour lines based on the mesh, click RhinoTerrain, Terrain, Analyze, Contour Lines. Then, select the mesh and specify the intervals for the contour lines (this is what the PrimaryCurveInterval and SecondaryCurveInterval options mean). Again, make sure you click Complete to finish the operation. If you are still in Rendered View mode you won’t be able to see the lines, so switch to Shaded or Wireframe and hide the mesh and point cloud to see the contour lines clearly.
6. Finally, another type of operation you can perform using RhinoTerrain is to calculate the “View Shed”. That means calculating what part of the terrain is viewable from a single point. This is really useful if you want to analyze the views or obstructions from a specific point. To do this, first hide the contour lines, bring back the mesh and the point cloud and go back to Rendered View mode. Once you do this, click RhinoTerrain, Terrain, Analyze, ViewShed, and select the observer position (you can use one of the points in the Point Cloud). Then, select the mesh, and then select any obstructing objects (if there aren’t any, just click return). Once you do this, RhinoTerrain will shade the parts of the terrain that are viewable from that point. It will also open up a window with different options. Here you can change the sun orientation, intensity and inclination, and change the colors of the shading.
7. In addition to these functions, RhinoTerrain also allows you to modify the mesh and rebuild it using contour lines. These options will be under RhinoTerrain, Terrain, Edit. You can also export your terrain to a Zcorp 3D printer.
1. You can also use .dem files to generate point clouds in RhinoTerrain. These .dem files can be downloaded from MassGIS (http://www.mass.gov/anf/research-and-tech/it-serv-and-support/application-serv/office-of-geographic-information-massgis/datalayers/imgelev5k.html) for Massachusetts or from the USGS site (http://earthexplorer.usgs.gov/) for the whole country. Once you have the .dem file the procedure is fairly straight forward. Click RhinoTerrain, PointCloud, Import, Elevation, and select the .dem file. Your file should be fine with the default coordinate system, so click OK on the next window. Once you do this, RhinoTerrain will generate a new point cloud from your terrain file. Again, you can convert this into a mesh, analyze it and modify it using RhinoTerrain.
Material for this tutorial is adopted from Columbia GSAPP.