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Which of the instrument used for tacheometry survey
Stadia road
Tacheometer
Chain
Both A and B
Both A and B
Tacheometry is a branch of angular surveying in which the horizontal and vertical distances of points are determined by optical measurements, eliminating the need for direct chain or tape measurements. A tacheometer (a transit theodolite fitted with a stadia diaphragm) and a stadia rod (or leveling staff) are the primary instruments used together to perform tacheometric surveying.
Tacheometry is a branch of angular surveying in which the horizontal and vertical distances of points are determined by optical measurements, eliminating the need for direct chain or tape measurements. A tacheometer (a transit theodolite fitted with a stadia diaphragm) and a stadia rod (or leveling staff) are the primary instruments used together to perform tacheometric surveying.
D=K⋅s+C — Horizontal distance for horizontal line of sight
D=K⋅s⋅cos2(θ)+C⋅cos(θ) — Horizontal distance for inclined line of sight
V=21K⋅s⋅sin(2θ)+C⋅sin(θ) — Vertical distance component
Tacheometry works on the principle of isosceles triangles, where the ratio of the distance of the base from the apex to the length of the base is constant. The vertical angle and the staff intercept (difference between upper and lower stadia hair readings on the stadia rod) are measured to compute horizontal and vertical distances using optical constants.
A tacheometer is a transit theodolite equipped with a stadia diaphragm containing two extra horizontal cross-hairs.
A stadia rod (or stadia staff) is specially graduated to allow clear reading of staff intercepts over long sight distances.
The multiplying constant K=if is typically manufactured to be 100.
The additive constant C=f+d is usually kept as 0 by incorporating an anallatic lens inside the telescope.
Rapid surveying in rough, broken, or steep terrain where chaining is difficult or impossible.
Measures both horizontal distance and vertical elevation simultaneously without direct physical measurements.
Lower precision compared to precise chaining or Electronic Distance Measurement (EDM) over long distances.
Sight lines can be obscured by vegetative cover or atmospheric refraction errors.
Preparation of contour maps and topographic surveys in hilly or undulating areas.
Location survey work for railways, highways, and reservoir site selection.
Chain (Option C) is used for direct linear measurements in basic linear surveying, not in optical tacheometric surveying.
Option A (Stadia rod) and Option B (Tacheometer) work as a pair; hence both instruments are required for a complete tacheometric setup.
D is correct — Both the tacheometer (transit theodolite with stadia diaphragm) and the stadia rod (leveling staff) are essential instruments used together in tacheometry.
Always remember for exam questions: if an anallatic lens is fitted in the telescope of a tacheometer, the additive constant C becomes zero (0) and the multiplying constant K is held fixed at 100.