What is the reference line for measuring north/south distances?

The Equator serves as the reference line for measuring north/south distances on the Earth's surface. It is an imaginary line that divides the Earth into the Northern and Southern Hemispheres and is situated at zero degrees latitude. Distances north and south of the Equator are measured in degrees of latitude, with the North Pole at 90 degrees north and the South Pole at 90 degrees south. This system allows for precise navigation and geographical reference across the globe, making the Equator the fundamental baseline for establishing latitude.

In contrast, while the Prime Meridian is significant for measuring east/west distances (longitude), it does not pertain to north/south measurements. The 180th meridian is also related to longitude and serves as the anti-meridian to the Prime Meridian. The Tropic of Cancer, situated at approximately 23.5 degrees north latitude, is important for solar calculations but not for establishing the basic system of latitude measurements that begins at the Equator.