Survey Lines:

The lines joining survey stations are the survey lines. The survey lines among main stations are therefore known as main survey lines or chain lines. The longest of the main survey line is generally known as Base Line running primarily by the middle of the area to be surveyed. The framework of triangles shall have one or two base lines since the whole survey is built around base line. It shall be measured along with higher care and accuracy.

The survey line joining tie stations or the subsidiary on main line is termed Tie Line. Those are run to account for interior details on the field, e.g. buildings etc.

Apart from tie lines and main, other survey lines are also selected for cross checking the accuracy of survey measurements. Such lines are called as check lines or proof lines. That is preferable to have at least one check line in each triangle of the framework.