Navigation means monitoring craft from here to there
Navigation studies how to track and steer vehicles between places. Marine practice keeps ships safe with charts and position fixes; the English word arrives in the 1530s from Latin navigatio, rooted in sailing. Polynesian wayfinders crossed open ocean by reading stars, swells, and wildlife long before any compass.
Navigation is the study of monitoring and steering a craft or vehicle from one place to another, and it splits into land, marine, aeronautic, and space branches. At sea it means moving ships and boats safely on or under the water by plotting positions on paper or electronic charts, with the required equipment set by the SOLAS Convention according to a ship's size. The English word dates from the 1530s, from Latin navigare, to sail, built from navis, ship, and agere, to drive.
Polynesian voyaging was probably the earliest open-ocean navigation, relying on memory, star motion, weather, wildlife, and wave size, with swell patterns recorded on Marshall Islands stick charts. Instruments such as the mariner's astrolabe came into use in the medieval Mediterranean, and one of the oldest surviving sea charts, the Carta Pisana of 1275, is drawn on sheepskin. From 1418, sponsored by Prince Henry, the Portuguese worked down Africa's Atlantic coast, and in 1488 Bartolomeu Dias rounded into the Indian Ocean.
Astrolabe, quadrant, backstaff, and compass carried the Age of Discovery, and spherical trigonometry and logarithms sharpened reckoning from the 1700s. The sextant, chronometer, and compass then dominated until twentieth-century radio navigation and gyrocompasses, themselves displaced by computers and satellite positioning. Today most positions come from receivers reading satellite signals.
A position is given as latitude, the angle north or south of the equator from 0 to 90 degrees, and longitude, the angle east or west of Greenwich up to 180 degrees; Sydney lies near 151 degrees east. A rhumb line crosses every meridian at the same angle, so a ship holding one compass bearing follows it. Without satellites, navigators draw lines of position from bearings, or circles from measured distances, and where two or more cross they have a fix; with only one, they weigh it against dead reckoning for an estimate.
Source: Navigation
