Meridian
Meridian is a reference direction with respect to which the direction of lines are mentioned. There are three types of meridian - True Meridian, Magnetic Meridian & Arbitrary Meridian
1 - True Meridian
It is the reference direction of north pole of earth from a given station point. It is also called geographic meridian.
2 - Magnetic Meridian
It is the direction of north pole indicated by magnetic needle.
3 - Arbitrary Meridian
This is any assume di