I am planning on creating a large terrain area (36km x 25km) that will require a multi-terrain tileset. It is based on a real world area with many roads, towns, forests etc. I have DTED2 (30m height posts) for terrain and Shapefile data for the features. It will be used for a tank simulator on a high end desktop PC. It does not need to look like a AAA game just good enough. Obviously I cannot hand paint the entire thing so some kind of software tool will be required to semi-automate the process. Cheaper is better but I do have some budget up to $3k ish.
I am pretty sure I will need some kind of paged loading of the terrain and features but I am unsure what product (if any) can achieve this with Unity. I suspect that merely deactivating the rendering of terrain that is not visible will not work because the total dataset will probably exceed 4Gb.
I have checked out the websites of the following tools but still not sure what to go for -
Terrain Composer, World Machine, Grome.