longitudes which are also known as the meridians are imaginary lines that divides the earth by running north to south from pole to pole, but measure the distance east or west of the central line that divides the earth into two parts .
This line is known as the GreenWich Meridian which passes through a city called Greenwich, England.
Longitudes are lines running from north pole to south pole and parallel to the greenwich meridian.
The greenwich meridian is the reference line from which positions of other meridians on the earth’s surface are measured in degrees east or west.
Consider the figure below.
using figure above as a reference; The longitude passing through C to South pole is α west of the Greenwich Meridian. The longitude of the meridian through B to south pole is θ east of the Greenwich Meridian.
A cross sectional view from north pole for the some lines of longitudes is as in figure below
- The meridian directly opposite the Greenwich is 180o East or West.
- The maximum angle of longitude is 180o E or W