> I'm wondering how this works on sloping ground. Like, if you're doing a
> pole barn and the ground slopes 8" down over 24'. Seems like if you fix
> an end to a high side pole then walk around with the other end, when you
> are marking poles also on the high side the water will be higher than if
> you're marking poles on the low side.
>
> Obviously the water will be level between two points, but wouldn't there
> need to be a correction made if you're doing it all between multiple
> points, since the bulk of the water in the tube may be higher or lower,
> depending on where most of the tube is on the slope?
Nope. Regardless of the location of the intervening tube, the end points
will be level to a high degree of accuracy. Errors due to local gravitation
gradients (including tides) will be microscopic. And most people define
"level" to be equal gravitational potential anyway. Otherwise you wind up
with water that runs uphill and so on.
Randall
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