Above is a movie showing the programs used to optimize the first model attempt and the workflow used to import it all into a Unity terrain.
There will be a later video showing the process of converting an object to a terrain and as such, this video does not show that process.

Reconnaissance II

Houndtor Rocks are also to feature in the game and so have also been photographed for reference to modelling in the game.

Below are the resized results.....