"RoyJ" wrote in message
news
If you put a laser level in the center you are going out 12', it won't
be out by much. Plus this is a rough excavation prior to filling with
concrete or gravel. Do you REALLY need accuracy in the +/- .060" range?
A water level is a pain to use in an excavation. Every time you move one
end, you adjust the water level in the OTHER end. Requires setting up
both ends, then remeasuring your reference end. Lots of chance for error.


That's why you want to use a large reservoir at one end...

As for accuracy, I have a Hoppy split level transit, all plastic, $30
or so, that will easily measure the thickness of a dime at 15', and is
MUCH more convienient than any water level. I use it for measuring floor
and structural issues in old houses. And, yes, I have calibrated it and
done repeatability testing.