when in doubt call...foul?

[Blue37]

I sometimes encounter fields with no line past first or third base base, and also see fields with a line on the grass past first and third, but no line on the dirt between the bases and the grass. In either situation, we pregame it so the plate ump has fair/foul responsibility for balls hitting in those areas. He can establish a frame of reference by looking at the base and home. The field ump has no such frame of reference.