COMPONENTS PARTS OF A THEODOLITE:
Leveling head: It supports the main working parts of the instrument and screw on
the tripod.
The head comprises of two parts:
• Leveling base or tribrach fitted with leveling foot screws for leveling the
instrument.
• Movable head or centering arrangement for centering the vertical axis
accurately over the station.
Lower circular horizontal metal plate:
It carries a circular graduated arc. It is
silvered and graduated from 00 to 3600 in a clock wise direction.
Upper circular horizontal metal plate: The upper plate carries an index and
vernier to Read fine reading on the graduated horizontal circle.
Telescope: Fitted to a horizontal axis, it consists of eye piece and diaphragm at
one end and objective glass at the other end.
The telescope has focusing screw by
which any Object can be bisected.
Circular graduated arc on a vertical circle: It is attached to the horizontal axis of
the telescope. It is usually divided into 4 quadrants, but in some instruments it is
graduated from 00 to 3600 the sub divisions of the vertical circle are similar to
those of horizontal circle.
Vernier frame: carrying an index and verniers to measure vertical angles.
Lower clamp and lower tangent screw: A lower clamp, clamps the lower plate
and the lower tangent screw enables finely controlled circular motion of lower
plate.
Upper clamp and upper tangent screw: An upper clamp, clamps the upper plate
to lower one, and the upper tangent screw enables finely controlled circular
motion about vertical axis.
Vertical circle clamp and tangent screw: A vertical circle clamp, clamps the
vertical circle and its tangent screw enables a finely controlled circular movement
to be given to the combined telescope and vertical circle about the horizontal
axis.
Circular level: It is located on the top of tribrach.
Plate level: It consist of plate bubble, which keeps the instrument parallel to
horizontal axis.
Compass: A circular or trough compass may be mounted on the vernier plate
between the standards for observing bearings.
Tripod: Theodolite is mounted and fixed on the tripod for each set up. As tripod
has adjustable legs, theodolite can roughly leveled with the adjusting the legs of
tripod.
