explain various obstacles in chaining and ranging?
Type # 1. Chaining Free, Vision Obstructed:
The ends of the lines are not intervisible in this form of barriers, such as raising terrain, a slope, or a jungle interfering.
Two scenarios could occur in this situation:
All line ends can be visible from some intermediate point on the line, such as a slope. This type of barrier can be easily overcome using reciprocal ranging and the stepping method of chaining to calculate length.
(ii) In certain cases, such as in a jungle, neither end can be visible from any intermediate point. This type of barrier can be overcome using the "random line approach."
Type # 2. Chaining Obstructed, Vision Free:
A sheet of water, whose diameter in the measuring direction exceeds the length of the chain or tape, is a common obstacle of this kind. The task is to calculate the distance between two suitable points on the chain line on each side of the barrier.
Two scenarios could occur:
(a) Where the barrier, such as a pond or a thorny hedge, maybe chained over.
(b) Where the barrier, such as a river, cannot be chained across.
Type # 3. Chaining and Vision Both Obstructed:
A house is a good example of this kind of barrier. In this case, the challenge entails extending the line past the obstruction and determining its distance.