device, called a compensator (fig. 15-41), makes this
possible. The compensator is suspended on fine,
nonmagnetic wires. The action of gravity on the
compensator causes the optical system to swing into
the position that defines a horizontal line of sight. This
horizontal line of sight is maintained despite a slight
out-of-level telescope or even a slight disturbance
occurs on the instrument.
TRIPOD
The tripod (fig. 15-42) is the base or foundation
that supports the level instrument and keeps it stable
during observations. A tripod consists of a head to
which the instrument is attached, three wooden or
metal legs that are hinged at the head, and pointed
metal shoes on each leg to be pressed or anchored into
the ground to achieve
In setting up the
strap from around the
a firm setup.
tripod, loosen the restraining
three legs. An effective way to
set the tripod down is to grip it with two of the legs
close to your body while you stand over the point
where the setup is required. By using one hand, push
the third leg out away from your body until it is about
50 to 60 degrees with the horizontal. Lower the tripod
until the third leg is on the ground. Place one hand on
each of the first two legs, and spread them while taking
a short backward step, using the third leg as a pivot
point. When the two legs look about as far away from
the mark as the third one and all three are equally
spaced, lower the two legs and press them into the
Figure 15-42.—Tripods.
Figure 15-41.—Self-leveling level compensator.
15-24
