Degree-Dependent
Degree-dependent refers
to the fact that these devices (laser levers and transits) need to be
set-up in a perfect 90 degree angle to the earths' center before they
can be used (figure 1).
figure 1
If
there is any movement after the initial set-up, then an error will occur
in subsequent measurements. The longer the distance from the unit - the
larger the error (figure 2). An error of just 1/2 degree at the
unit will result in an error of over 10" at 100'. One-half
degree is very little, barley perceptible to the human eye, this is why
devices which rely on bubble-levels are the most prone to this type of
error, while auto-leveling units aren't.
figure 2
