What is prime meridian

a planet's meridian adopted as the zero of longitude.

A prime meridian is the meridian in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian form a great circle. This great circle divides a spheroid into two hemispheres.

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The prime meridian is the line drawn north to south at 0° (0 degrees) longitude. It is an imaginary line on Earth that passes north to south through the Greenwich Observatory in London, England. Sentences: The prime meridian divides Earth into the Eastern Hemisphere and the Western Hemisphere.

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