There is no spline support currently, so drawing accurate and sharp-edged shapes in specific configurations isn't really possible in-app. There is the Painted Shader, which you can use to "paint" textures and displacement, but it is not so great for doing highly technical and specific work. You could, however, create the shapes/maps/etc. in another app, even a normal image editing app like Photoshop, and import it as mask/displacement map, etc. I think you will probably end up frustrated if you try to create the entire golf course layout realistically in Terragen though.
- Oshyan