NavMesh - fatal error during baking

Hi. My map is big terrain which consist of 4 smaller terrains (3000 x 3000 units each). On the map there are a lot of objects (trees, buildings, etc.). When I clicked "Bake" Unity crashed with message "fatal error". In details I saw there is a problem with memory. I laso tried to bake the navigation in batchmode to save some memory, but Unity still crashes.

I guess this problem is connected with Unity's architecture (x86) and memory limit for one process.

Is there any solution for this problem?

Regards, Stopero

Edit: Solved. Changing heightmap resolution from 4097 to 2049 (with graphic app) solved the problem.