THEODOLITES

            Theodolites are precision instruments used extensively in construction work for measuring angles in the horizontal and vertical planes. Two types of theodolite are vused and these are either optical theodolite which need to be read manually or electronic theodolite which are capable of displaying readings automatically.

            Many different  theodolites are available for measuring angles and they are often classified according to the smallest reading that can be taken with the instrument. This can vary from 1’ to 0.1” and, for example, a 1” theodolite is one which can be read to 1” directly without any estimation.

At this point, it is worth noting that a full circle is 360⁰ or 400

Basic Components of an optical theodolite

All types of optical  theodolite are similar in construction. The various parts of the theodolite and their functions will now be described.

            The trivet stage forms the base of the instrument and in order to be able to attach the theodolite to the tripod, most tripod have a clamping screw which locates into a ⁵/₈ inch threaded center on the trivet . this enables the theodolite to move on the tripod head and allows the theodolite to be centered. The trivet also carries the feet of three threaded levelling footscrews. The tribrach su