A nautical mile is a unit of distance used historically and currently in maritime navigation, defined by the length of one minute of arc of latitude on the Earth's surface. It is not precisely equivalent to terrestrial miles, varying slightly depending on the specific geodetic datum and the latitude of measurement. The standardized definition relates the unit to the geometry of latitude lines, making it inherently tied to celestial navigation and global mapping. Because of its historical connection to sea travel and its basis in the Earth's curvature, it remains a critical measurement for naval operations and oceanic charting.