Terrain is important to many SketchUp modelers: Your building needs ground to stand on, or maybe you’re modeling the ground itself to create a landscape. But wait. SketchUp’s Sandbox tools — the tools you use to model terrain — can also create forms completely unrelated to terrain. How can terrain include all these other possibilities? The secret is in the hidden geometry. When you’re modeling terrain (or other shapes) with the Sandbox tools, you’re technically sculpting a special type of geometry called a TIN, or triangulated irregular network. That’s a fancy way of saying, “a group comprised of triangles.” The following figure shows a flat TIN that hasn’t been sculpted into anything yet. In the next figure, you see an example of a TIN sculpted into hills and a watery valley. The Sandbox tools are traditionally used to create this type of terrain. In the following sections, you find out how to start modeling TINs, where to find the Sandbox tools, and what it means to geolocate terrain. After you cover the basics, you also find pointers to how to start sculpting a TIN. To create a TIN, you can import contour lines from another program or import terrain from Google Earth via SketchUp’s built-in tools. You can also transform contour lines that you draw yourself into a TIN, or draw a plain flat rectangular TIN like the one shown earlier in this article. To get started, see Importing Preexisting Terrain and Creating Terrain from Scratch. After you have a TIN in SketchUp, learn how to toggle the TIN’s visibility, sculpt and fine-tine its features, and place other items on its surface. You find the Sandbox tools on the Sandbox toolbar or by selecting Tools >, Sandbox and selecting your tool of choice from the submenu. As you read through this article’s subarticles, you find out how to use each tool for its respective task. If you’re modeling terrain, you can geolocate it, or embed geographical coordinates that place your terrain at a specific point on Earth. Geolocated models (or geomodels for short) offer a number of advantages: For details about shadow studies and viewing a model in Google Earth, see Communicating Your Designs. As you model your terrain, know that you can geolocate it by importing terrain from Google, as explained in Importing Preexisting Terrain. Also, Modeling Terrain for Google Earth offers tips and tricks that can improve your model’s appearance in Google Earth. Source.