STUDY OF THEODOLITE
TRANSIT THEODOLITE:It consists of a telescope which can be revolved through a complete revolution about its horizontal
axis in a vertical plane.
PARTS:Leveling head, telescope, vertical circle, index frame, A frame lower plate, upper plate, level tubes,
LEVELING HEAD:The leveling head consists of two parallel triangular planes known as tribrach plates. The upper
tribrach has three arms, each carrying a leveling screw. The lower tribrach has three arms each carrying a
leveling screw. The lower tribrach plate or foot plate has a circular hole through which plumb bob may be
TELESCOPE:The telescope is an integral part of the theodline and is mounted on a spindle known as horizontal
axis or trunnion axis. In most of the transits, internal focusing telescope is used.
VERTICAL CIRCLE:The vertical axis is a circular graduated arc attached to the trunnion axis of the telescope
consequently the graduated arc rather with the telescope when the latter is turned about the horizontal axis.
INDEX FRAME:- The index frame is a T-shaped frame consisting of a vertical leg known as clipping
arm and a horizontal bar known as vernier arm of index corm. At the two extremities of the index arm are
fitted two verniers to read the vertical circle.