Theodolite is an instrument which replaced compass and level. It can measure both horizontal and vertical angles. If telescope is kept at zero reading of vertical angle it serves as an ordinary level. In this modern era of electronics equipments have come up to measure the distances to relieve surveyor from chaining long lines. Total station is another modern survey equipment which combines the features of theodolite and electromagnetic distance measurement (EDM) instruments. Global positioning system
is an instrument, which establishes global position of the station making use at least 4 satellite stations. In this chapter all these modern tools of surveying are briefly explained.
THEODOLITE
It is a commonly used instrument for measuring horizontal and vertical angles. It is used for prolonging a line, levelling and even for measuring the distances indirectly (techeometry). Using verniers angles can be read accurately up to 20″. Precise theodolites are available which can read angles up to even 1″ accuracy. They use optical principle for more accurate instruments. Now a days electronic theodolites
are also available which display the angles. In this article construction and use of vernier theodolite is explained.
