Question

PART-2 (12 Marks) Q5. i. List any four types of obstacles in chaining. ii. Discuss the same with neat labelled sketch and explain the principles how to solve it? 141

Answer 1

5. i)The types of obstacles in chaining are

• Chaining is free but vision is obstructed
• Chaining is obstructed but vision is free
• Chaining and vision are both obstructed

ii)

• Chaining is free but vision is obstructed- Both ends of the line may not be visible from intermediate points on the line. This problem arise when a rising ground or a jungle area interrupt the chain line.

  

c A B D E

This obstacle can be solved by measuring along a random line as shown in the figure above.

• Chaining is obstructed but vision is free-Both ends of the chain is visible from any intermediate point but prevents chain from measuring directly between two points. Like when a river or pond is in the chain line.

с D Α. F B E

This obstacle can be solved by some indirect measurements. Like in the figure, instead of ABEF, line ABCDEF is used.

• Chaining and vision are both obstructed- When chaining and vision are both obstructed. This problem arise when a building come across the chain line.

G H A B E F

This obstacle can be solved by choosing two points A & B to one side and make perpendicular AC and BD of equal length. Then join CD extend it past the obstacle choose two points G and H on CD and make GE and HF equal to that of AC and BD. Join EF and extend it. Measure DG since BE = DG.