Test: Surveying- 1 - GATE MCQ

Sensitivity of a bubble tube/ level tubs is its capability of exhibiting small deviation of the tube horizontally.

Sensitivity increases when:
    Temperature Decreases
    Larger Radius of Curvature
    Larger diameter
    Larger Length
    Higher length of one division
    Higher smoothness of finish of internal surface of liquid
    Low surface tension and viscosity

Types of survey on the basis of place
Land Survey: Done on Land
Hydrographic Survey: Survey of water bodies like streams, sea, ponds etc. 
Underground Survey: required for construction of tunnels.
Aerial Survey: Aerial photographs via aeroplanes, drones etc. Preparation of large scale maps of an area.
 

When tape is supported at two ends then it will always sag downwards due to its own weight, thus, apparent length larger than the given length. The correction is always negative and is given by-

C_g=(w² l³)/(24P² )
w weight per unit length
P applied pull
l  length of tape suspended between the supports.

As it can be seen from the figure the quadrantal bearing is N44°40′W

Let the collimation error per 100m is e
Correction for staff reading at A = (25/100)e= 0.25e
Correction for staff reading at B = (50/100)e =0.5e
True staff reading at A = Observed Value + Correction = 2.847+0.25e
True staff reading at B = 3.462+0.5e
From Reduced Level Readings
Difference in elevation = RLa – RLb =283.665-284.295= -0.63m
= True Staff Reading at A- True Staff Reading at B 
=2.847+0.25e-(3.462+0.5e) = -0.615-0.25e =-0.63

e = 0.06m

Correction per tape length is given by: (Coefficient of Linear Expansion) x (Change in Temperature) x (Tape Length)
= 10-6 x (30-20) x 50 = 0.0005 m 

Representative fraction of the map (in terms of length) =√((Area on Map)/(Actual Area of plot))
Area on Map = 1 cm² = 1 x 10^-6 m²
Actual Area of plot = 16 km² = 16 x 10⁶ m²
Representative fraction of the map (in terms of length) = √(〖10〗(-6)/(16×〖10〗⁶ )) =1/4000000

D = KS + C

 S  = 2.830 - 1.726 = 1.104

D = 100 x 1.104 + 0.4 = 110.8m