the prime meridian
That's the imaginary cricle comprised of the Prime Meridian and the meridian of 180 degrees longitude.
It is the "Prime Meridian" or the "0 degree Meridian" which is the basis for calculating time in most of the world.
The Prime Meridian.
Equator
The imaginary line at zero degrees longitude is the Prime Meridian. The imaginary line halfway between the poles is the Equator. The Equator is zero degrees latitude.
The Prime Meridian
The prime meridian.
It is the Prime Meridian
The Prime Meridian.
The Prime Meridian.
That's the 'Prime Meridian'.
Prime Meridian