Adjusting the scale of terrain materials?

Hi folks,

I am trying to make a terrain which is aesthetically pleasing when viewed from an above angle. Unfortunately, terrain layer materials appear to be locked at a resolution of 1m*1m, which produces a grid-like effect when viewed from above:

REMOVEDUPLOAD

I've rummaged through the various terrain-related options, but couldn't find anything that can address this. Is there a way to adjust terrain materials to appear at different values, or should I be taking a different approach entirely? Any advice on improving the look of terrain from an overhead angle would be appreciated.

Thanks,

Soft