Aww....everyone beat me to this one. I'm not sure if there's some hidden agenda in there somewhere, but okay I'll repeat what's already been said.
A level's more or less calibrated by the Earth's spherical electric field. The Earth isn't a perfect sphere, but it's close enough for the sake of surface observation. I guess a standard would be under such conditions to prevent influence from bodies other than the Earth.
Blah...I wish I actually knew stuff rather than drew conclusions without any prior research or thought. Not that this is a particularly difficult question. It's just a little more black and white than the last, and it's easier to BS "grey area" questions. :mellow:
A level's more or less calibrated by the Earth's spherical electric field. The Earth isn't a perfect sphere, but it's close enough for the sake of surface observation. I guess a standard would be under such conditions to prevent influence from bodies other than the Earth.
Blah...I wish I actually knew stuff rather than drew conclusions without any prior research or thought. Not that this is a particularly difficult question. It's just a little more black and white than the last, and it's easier to BS "grey area" questions. :mellow: