Short answers, pulled from the story.
Navigation is the field of study focused on monitoring and controlling the movement of a craft or vehicle from one place to another. It includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation. All navigational techniques involve locating the navigator's position against known locations or patterns.
Polynesian navigation is probably the earliest form of open-ocean navigation, based on memory and observation. Early Pacific Polynesians used the motion of stars, the weather, the position of certain wildlife species, and the size of waves to travel between islands, recording knowledge on instruments like the Marshall Islands Stick Charts of Ocean Swells.
Longitude can only be calculated if the precise time of a sighting is known, and reliable marine chronometers were unavailable until the late 18th century and not affordable until the 19th century. From about 1767 until about 1850, mariners lacking a chronometer used the method of lunar distances to find Greenwich time and their longitude.
Celestial navigation is based on observing the Sun, Moon, planets, and navigational stars with a sextant, which measures a body's angular height above the horizon. A navigator shoots several stars in succession to produce overlapping lines of position, and where they intersect is the celestial fix. A nautical almanac and a marine chronometer are used to compute the body's subpoint on Earth.
Satellite navigation began after the first experimental satellite launched in 1978. As of 2024 the operational systems include the United States NAVSTAR GPS, the Russian GLONASS, the European Union's Galileo, and China's Beidou, with over 100 satellites in medium Earth orbit and stated accuracy between 1 and 10 metres.
An inertial navigation system is a dead reckoning system that computes its position from motion sensors, reading acceleration from accelerometers and rate of rotation from gyroscopes. It needs no outside information and cannot be jammed, but its errors accumulate over time. The first inertial system is considered to be the V-2 guidance system the Germans deployed in 1942.
The term navigation stems from the 1530s, from the Latin navigare, meaning to sail, sail over, go by sea, or steer a ship. It draws on navis, meaning ship, and the root of agere, meaning to drive.