n.本初子午线，本初子午圈

本初子午线；[天]本初子午圈

prime meridians───本初子午线；[天]本初子午圈

principal meridian───主子午线

antemeridian───adj.上午的

ephemeridian───星历

postmeridian───adj.午后的；午后发生的

prime ideal───[数]素理想

prime vertical───[天]卯酉圈；东西圈；主垂线

prime verticals───[天]卯酉圈；东西圈；主垂线

magnetic meridian───[天][地物]磁子午线

By agreement, the longitude passing through Greenwich of Observatory is called the prime meridian.───按照约定, 经过伦敦格林尼治天文台的经线被称为本初子午线(零度经线).

So the Martian prime meridian, the equivalent of the Greenwich, UK, prime meridian on Earth, has been set to run through this region.───因此，火星本初子午线，在格林威治，英国，地球上的本初子午线，相等于已被设置为贯穿这一地区。

Yes this is the…is the prime meridian if you like. The line that separates the eastern hemisphere from the western hemisphere.───是的，这就是本初子午线，它把地球分为东半球和西半球。

meridian, becomes the world coordinates.───本初子午线，世界时间的起点。

Yes this is the...is the prime meridian if you like. The line that separates the eastern hemisphere from the western hemisphere.

The placement of the prime meridian is a purely political decision.

Yes this is the...is the prime meridian if you like.

The prime meridian of longitude is in Greenwich, South London.

The prime meridian is at 0 degrees longitude, and the international date line is at 180 degrees. The equator is at 0 degrees latitude.

So the martian prime meridian, the equivalent of the Greenwich, UK, prime meridian on Earth, has been set to run through this region.

Starts to the prime meridian, becomes the world coordinates.

He said: "I just crossed the Prime Meridian and reached the Western Hemisphere!

Ptolemy was free, however, to lay his prime meridian, the zero-degree longitude line, wherever he liked.