It may be defined as:
A Change Point ( C.P) is a point which shows the shifting of the level. It is a point on which fore and back sights are taken. Any stable and well defined object such as boundary stone, curb stone, rail, rock, etc., is used as a change point. A Benchmark may also be taken as change point. It is also known as turning point. (T.P)
Any point whose elevation is to be determined is known as station. Or a point which is to be established at a given elevation. It is the point where the staff is held not the point where the level is set up.