It is an instrument of measuring the distance between to pints on the surface of the earth. We can measure distance with this speedily. Commonly we use tape or chain for measure the distance. If there is any rise or fall between points so we feel difficult to measure the distance between them.

We need more time and work hard for this. For measure the distance with distance meter keep it on one point and reflector keep on second point. Some rays reflect so we get distance between them.