I just found the manual online and it says:
You are able to store over sixty thousand matrix planes at any one time. A matrix plane is best described as a landscape that has been cut into a grid pattern. You can modify the landscape by raising and lowering a point on the grid, terra forming it to whatever you want. Additionally, you can apply a special texture that can contain several different styles of floor. These floor textures can then be mapped onto a point on the grid allowing you paint your landscape anyway you want. To make the matrix even more powerful, you can shift the matrix in any direction and it will automatically wrap around to effectively create an infinite landscape!
Is there a way to get more than 60,000 planes?
Or maybe a way to store and load them quickly in LOD applications?