For extremely large-scale units, the shadowing from shadow depth maps may be inaccurate due to the incorrect scale of the near and far clipping planes of the shadow render.
The following example shows you how to manually set the near and far clipping planes of the shadow depth map render (it assumes you have a shadow casting light called lightShape):
setAttr lightShape.useDmapAutoClipping 0;
setAttr lightShape.dmapFarClipPlane 10000;
setAttr lightShape.dmapNearClipPlane 0.01;
where the first line turns off the automatic generation of near/far clipping planes, and the last two lines let you set the near/far clipping plane values appropriately.