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.

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.

Dave Hinz wrote:
On Thu, 10 Mar 2005 14:28:08 GMT, RoyJ wrote:

You can do a nice job with one of the el-cheapo laser levels. This one
is $10 at Harbor Freight.


Problem with a laser level, is you get a nice straight line, but your
level is only as good as that bubble on that tiny level. For a few
feet, you're probably right on. But, how much error in that bubble would
it take to be off by an inch, at 50 feet? Not a hell of a lot. Water is
much more dependable, can't be mis-calibrated, and has been in use as a
level for laying out buildings, since the pyramids were built.