Isogonics lines are the lines having the same

A relatively fixed point of known elevation above datum, is called

Profile levelling is usually done for determining

Pick up the most accurate statement from the following.

Reciprocal levelling eliminates

Reduced bearing is:

If the back sight and fore sight distance are kept equal during levelling observations, then the effect of both refracti…

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

In case of a double line river, contours are