I have been looking at the EA tiger woods golf game http://tigerwoodsonline.ea.com/ and i was wondering how they make those clean sharp curved bunkers and fairways on the terrain. I have tried to do the same myuself but always end up with jagged edges on the curves. I have tried with several dirrerent resolutions of heightmap and textures but no good. I know why my examples look the way they do but how did they do it in the tiger woods game (also made in unity 3d as far as i am aware)
The terrain engine uses a grid for placement and thus limited by the resolution of the grid. If you really want smooth curves you either make the terrain completely as a mesh, or you use the terrain engine for the basic shape and use meshes for the detailed parts. The biggest challenge with a mesh as terrain is performance. If your terrain has lots of detail it will have quite an impact on performance, the terrain-engine falls back on lower resolution terrain further away. You could of course use LOD to have different quality terrain meshes for different distances, but beware of seams where hi-and-lo quality meets.
Why not model the whole terrain in 3D Modeling packages like Maya and Mudbox or Zbrush and create a height map on it.
you can do what you want with your terrain in 3D modeling packages and that would be closely what it looks when you export and import your height map in Unity Terrain.