Obstacles  to Ranging

These obstacles may be further sub divided into the following categories:

(a) From some intermediate points both ends of the line are visible. Intervening ground is an instance of such obstacle. This difficulty can be overcome by resorting to reciprocal ranging.

(b) From intermediate points on the line both ends of the line cannot be visible, but may be visible from a point somewhat away from the line. Intervening bushes and trees are the instance of such obstacles. This obstacle to chaining can be overcome by measuring along a random line as shown in given figure. In this case required length

                                          Obstacle to ranging