Ranging is used to locate intermediate points. They are marked using ranging rods. It is done when a survey line is very long and marks are required to distinguish line.

Offsets are taken perpendicular to survey lines. They are used to mark objects and lateral distance to m, using an offset rod.

Ranging is of 2 types â?? direct and indirect. Direct ranging is done using a line ranger or naked eye. Indirect ranging is done when starting and ending points are not visible. 

Angle ABC is 90°. From â??BCE, and CE = BC sec 45° = 100 Ã? 1.4142 = 141.42 m.

Obstacles to levelling is not a kind of obstacles to chaining. Obstacles of chaining are of three kinds. They are obstacles to ranging, obstacles to chaining, obstacles to both chaining and ranging.

There can be 5 types of chains used for chain surveying. They are metric chain, Gunterâ??s chain, engineerâ??s chain, revenue chain and steel band or band chain.

The three types are open cross staff, French cross staff and adjustable cross staff. Open cross staff has two vertical, opposite slits. French cross staff consists of a hollow octagonal box. The adjustable cross staff consists of two cylinders of equal diameter, one placed on top of or.