The plotting of small areas which can be commanded from a single station, is usually done on the plane table by the method of

The lines of force of earth's magnetic field are parallel to the earth's surface

An imaginary line joining the points of equal elevation on the surface of the earth represents

Accurate centering of a plane table is done by

Systematic errors are those errors

Perpendicularity of an offset may be judged by eye, if the length of the offset is

A fixed point of reference of known elevation is called

The angle of intersection of a curve is the angle between

The combined correction for refraction and earth's curvature (in levelling observations) is