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  APPARATUS :- Tachometer with stand, Ranging rods, Peg, Arrows, Tape, etc. THEORY :- Tachometer is a branch of angular surveying in which the horizontal and vertical distances of points are obtained. The method is very rapid and convenient.   Tachometer is the combination of transit theodolite and stadia diaphragm.   The stadia diaphragm essentially consist of one stadia hair above the other at an equal distance below the horizontal cross hair. PRINCIPLE OF TACHOMETER :- The Principle underlying tachometer is as follows. If   ‘C’ and ‘D’   be two points and if a Tachometer is a set up at ‘C’, the      horizontal distance of ‘D’ from ‘C’ and elevation of ‘D’ with respect to the instrument axis at ‘C’ can be obtained from, 1) The vertical angle from ‘D’ to ‘C’. 2)       The angle subtended at ‘C’ by a known distance on the staff held at ‘D’. this principle is utilized in different ways in ten above m...