The imaginary line passing through the intersection of cross hairs and the optical centre of the objective, is known as

The maximum allowable limit up to that a measurement may vary from the true value is known as

The curvature of the earth is taken into consideration if the limit of survey is:

While doing levelling in undulating terrain, it is preferable to set the level on:

An obstacle which obstructs both chaining and ranging may be

Short offsets are measured with

The first temporary adjustment of a prismatic compass is centering, levelling, for all

Reciprocal leveling eliminates

Reading of the metric levelling staff can be taken accurately up to