Civilwar-Day 13(Oct 7)-PWD-Chain,Compass & Plane table survey

What is the true distance between two points? Measured distance = 720 m. Length of chain = 20 m. Error in chain = (+) 4 cm.

• 720.44 m
• 721.44 m
• 722.44 m
• 723.44 m

Answer explanation

True length of chain = 20.04 m; Correction factor = 20.04/20 = 1.002. Therefore, True distance = 720 × 1.002 = 721.44 m.

Which line should be drawn first while plotting?

• Tie line
• Base line
• Chain line
• Check line

Answer explanation

The base line is drawn first while plotting as it serves as the main reference line from which the entire framework of the survey is constructed.

Which instrument is used for transferring the points to the ground while chaining on a sloping ground?

• Arrows
• Plumb bob
• Steel band
• Wooden peg

Answer explanation

A plumb bob is used to transfer points vertically from line to ground on sloping surfaces to ensure accurate alignment.

Bearing of AB is 160°, bearing of BC is 330°, then angle ABC is

• 30°
• 110°
• 170°
• 10°

Answer explanation

Bearing of AB = 160° → therefore bearing of BA = 160° + 180° = 340°

Bearing of BC = 330°

Hence,

∠ABC = |340° − 330°| = 10°

The latitude and departure of any point with reference to the preceding point are called

• Co-ordinates
• Consecutive co-ordinates
• Independent co-ordinates
• XY co-ordinate

Answer explanation

The latitude and departure of a point measured from the previous point are known as consecutive coordinates, used in traverse computations.

In prismatic compass, when the needle points to north, the reading under the prism should be

• 0°
• 90°
• 180°
• 270°

Answer explanation

In a prismatic compass, the graduations flow clockwise from 0° at South, 90°, 180°, 270° marks are provided at West, North and East extremities. When a reading is taken through the prism, the needle is pointed towards North while South end of the needle is under the prism, which reads 0° .  

Diurnal variation of magnetic declination is

• Greater at equator than nearer the poles
• Less at equator than nearer the poles
• Less in summer than in winter
• Same at all latitudes and during different months

Answer explanation

Diurnal variation of magnetic declination is less at the equator than nearer the pole

The fix of a plane table from three known points is good if

• Middle station is nearest
• Middle station is farthest
• Either the right or left station is nearest
• None of these

Answer explanation

In a three-point resection method of plane tabling, the fix is most accurate when the middle station is nearest to the plane table position.

This provides the best geometric condition for intersection, resulting in a well-defined and precise location on the map.

Intersection method of detailed plotting is most suitable for

• Forest
• Hilly areas
• Plains
• Urban areas

Answer explanation

The intersection method of plane tabling is most suitable for hilly areas where chaining is difficult and inaccessible points can be located by intersection of rays.

In plane tabling the method used for establishing instrument station is

• Radiation
• Resection
• Intersection
• Traversing

Answer explanation

The resection method is used in plane tabling to establish the position of the instrument station by observing known points.