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The initial setting operation includes fixing the theodolite on a tripod, along with approximate levelling and centering over the station mark.For setting up the instrument, the tripod is placed over the station with its legs widely spread so that the centre of the tripod head lies above the station point and its head approximately level (by eye estimation).
The permanent adjustments of theodolites are made to establish fixed relationship between the instrument's fundamental lines. The fundamental lines or axis of a transit theodolite include the following:- Vertical axis; Axis of plate levels; Axis of telescope; Line of collimation; Horizontal axis; Axis of altitude bubble and the vernier should ...
The term transit theodolite, or transit for short, refers to a type of theodolite where the telescope is short enough to rotate in a full circle on its horizontal axis as well as around its vertical axis. It features a vertical circle which is graduated through the full 360 degrees and a telescope that could "flip over" ("transit the scope").
A theodolite is used to measure the horizontal angle between indicators on the two ends of the subtense bar. The distance from the telescope to the subtense bar is the height of an isosceles triangle formed with the theodolite at the upper vertex and the subtense bar length at its base, determined by trigonometry .
The alidade is the part of a theodolite that rotates around the vertical axis, and that bears the horizontal axis around which the telescope (or visor, in early telescope-less instruments) turns up or down. In a sextant or octant the alidade is the turnable arm carrying a mirror and an index to a graduated circle in a vertical plane. Today it ...
A tribrach is an attachment plate used to attach a surveying instrument, for example a theodolite, total station, GNSS antenna or target to a tripod. A tribrach allows the survey instrument to be repeatedly placed in the same position over a surveying marker point with sub- millimetre precision , by loosening and re-tightening a lock to adjust ...
A total station or total station theodolite is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure both vertical and horizontal angles and the slope distance from the instrument to a particular point, and an on ...
Adjustments of theodolite may refer to: Permanent adjustments of theodolite; Temporary adjustments of theodolite; See also. Adjustment computations