Test: Linear Measurements - 1 - Civil Engineering (CE) MCQ

Invar tapes are used for linear measurement of very high degree precision such as base line measurements cloth or lines tap for rough and subsidiary measurements such as offset.

 Obstacles to chaining:

• Cases often occur in the field where the distance between two points is required, but direct chaining from one point to the other is impossible because of some sort of obstacle.
• A river and pond is an obstacle to chaining but not ranging.

Always negative, 

(Assuming parabola curve),
l₁ = length suspended (m)
p = pud applied (kg or N)
w = weight of tape per meter length
wl₁ = weight of tape suspended between supports

The maximum tolerance in 20 m chain is ±5 mm in 30 m chain is ±8 mm

Let 'L' be the distance measured along the slope inclined at angle 'θ' as shown in the figure:

Hypotenusal correction = Radial length on horizontal Plane - Projection of inclined length on a horizontal plane

∴ Hypotenusal correction = L - L × cos θ

∴ Correction = L × ( 1- cos θ) = 30( 1 - cos θ)

Therefore, correct answer is A.

Actual length of chain = 30 - 0.1 = 29.9 m

Distance between two points measured with scale of 1 cm to 20 cm 
= 468/20 = 23.4 cm
Actual scale of the plan is 1 cm = 40 m
∴ True distance between points
= 23.4 x 40 = 936 m