Latitude and longitude
Latitude and longitude are arbitrary measurements used to describe any point on the Earth, or similar globe. Borrowing from theories of ancient Babylonians, later expanded by the famous Greek thinker and geographer Ptolemy, a full circle is assigned 360 degrees. Latitude is the term for the distance from the middle of the circle, or, in the case of the Earth, the equator. The equator is designated 0 degrees, with each pole being 90 degrees. Longitude is the vertical measurement--current convention places the zero degree point at Greenwich, England (also known as the Prime Meridian), with 180 degrees being on the opposite point on the globe.
Lines of longitude are all of the same length whereas those of latitude vary in length.
Science fiction works, in particular, have expanded this concept by adding a third dimension, to describe directional headings of spacecraft.
See also
