2.7. Horizontal distance measurement on sloping ground

There are two methods for determining horizontal distances on sloping ground:

1. Direct Method
2. Indirect Method

1. Direct Method of distance measurement. 

• The horizontal distances are directly measured by the process of stepping. 
• This method is also known as 'Stepping method’

 Steps of Direct Method.

• Chaining is done from the top of the hill to the toe i.e. downhill.
• The follower holds the zero end of the chain at P on the ground and the leader with the other handle of the chain and a ranging rod moves in the forward direction at a convenient distance apart Say, PP₁.
• The leader then transfers the point P₁ to P₂ on the ground by the means of plumb bob (or dropping a pebble or an arrow)
•  Now the followers take the new position P₂ and direct the leader to move forward and stretch the tape or chain in a line of PQ and the new position is P₃.
• Now, the leader transfers the point P₃ to P₄ on the ground as done earlier.
• This process is repeated till point Q is reached.

Horizontal distance PQ=S₁+S₂+S₃+S₄+S₅.

2. Indirect method of Distance Measurement

• In this method, the sloping side is measured on the ground and later it is converted into horizontal equivalent using geometrical conditions
• The methods adopted for calculating horizontal distance indirectly:
  • By measuring angle of inclination. 
  • By measuring the difference of levels.