Mounting is done by engaging threads at the base of
the instrument (called the footplate) with the threaded
head on the tripod. These levels are the ones most
frequently used in ordinary leveling projects. For
rough leveling, the hand level is used.
Figure 5-2 shows a dumpy level and its
nomenclature. Notice that the telescope is rigidly
fixed to the supporting frame.
Inside the telescope there is a ring, or diaphragm,
known as the reticle, which supports the cross hairs.
The cross hairs are brought into exact focus by
manipulating the knurled eyepiece focusing ring near
the eyepiece, or the eyepiece itself on some models.
If the cross hairs get out of horizontal adjustment,
they can be made horizontal again by slackening the
reticle adjusting screws and turning the screws in the
This adjustment should be
performed only by trained personnel. The object to
which you are sighting, regardless of shape, is called
a target. The target is brought into clear focus by
manipulating the focusing knob shown on top of the
telescope. The telescope can be rotated only
horizontally, but, before it can be rotated, the azimuth
clamp must be released. After training the telescope
as nearly on the target as you can, tighten the azimuth
clamp. You then bring the vertical cross hair into
exact alignment on the target by rotating the azimuth
The level vial, leveling head, leveling screws, and
footplate are all used to adjust the instrument to a
perfectly level line of sight once it is mounted on the
You can save time using the self-leveling, or
so-called automatic, level in leveling operations.
The self-leveling level (figure 5-3) has completely
eliminated the use of the tubular spirit level, which
required excessive time because it had to be reset
quite often during operation.
The self-leveling level is equipped with a small
bulls-eye level and three leveling screws. The
leveling screws, which sit on a triangular footplate,
Figure 5-2.Dumpy level.