The Prime Meridian isn't really "marked by" anything. It is DEFINED by reference to the Royal Observatory in Greenwich, England. It is the zero point for the measurement of longitude east or west of Greenwich.
By a W for West
prime meridian!Prime Meridian!PRIME MERIDIAN!PrImE MeRiDiAn!
Everywhere on Earth has a meridian, which is the line through the point and also through the north and south poles. The prime meridian marks the meridian with zero longitude. It used to be marked by a line in the ground at the Greenwich observatory in London, but in GPS coordinates the prime meridian passes about 50 metres to the east of that line now.
Both of those longitudes are marked by the same meridian ... halfway around the globe from the Prime Meridian.
This is called the Prime meridian, it passes through Greenwich, England.
latitude
By a W for West
prime meridian!Prime Meridian!PRIME MERIDIAN!PrImE MeRiDiAn!
Everywhere on Earth has a meridian, which is the line through the point and also through the north and south poles. The prime meridian marks the meridian with zero longitude. It used to be marked by a line in the ground at the Greenwich observatory in London, but in GPS coordinates the prime meridian passes about 50 metres to the east of that line now.
Both of those longitudes are marked by the same meridian ... halfway around the globe from the Prime Meridian.
This is called the Prime meridian, it passes through Greenwich, England.
the prime meridian
prime the prime meridian
The vertical line is the Prime Meridian.
This is the Greenwich Meridian, the Prime Meridian of the World.
There is only a single Prime Meridian.
The prime meridian is at all latitudes.