Navigation is the science and technology of finding the position, course, and distance travelled by a ship, plane, or other craft. Traditional methods include the magnetic compass and sextant. Today the gyrocompass is usually used, together with highly sophisticated electronic methods, employing beacons of radio signals, such as Decca, Loran, and Omega. Satellite navigation uses satellites that broadcast time and position signals. The Phoenicians, Syrians, Carthaginians, Greeks and Romans conducted their voyages solely by the observation of the heavens, and by keeping as much as possible to the coast. It was not until the voyages made by direction of Prince Henry of Portugal, after 1418, that navigation seems to have been systematically conducted, and the sea-instruments and sea-charts then constructed formed the basis of maritime science until replaced by satellite
navigation equipment in the late 1990s. An early invention that marked progress was the cross-staff, first described by Werner in 1514. It was used for the determination of longitude, by observation of the distance between the moon and some star; and out of it grew the fore-staff and the back-staff. In 1530 Gemma Frisius of Louvain devised the idea of using small clocks in conjunction with instrumental observation, and the nautical quadrant in some form was thenceforth part of every ship' s furniture. John Davis' quadrant (the back-staff) seems to have been generally preferred for many years. In the early 16th century there also cam into use at sea the astrolabe, for taking the altitude of the sun and stars. This instrument was made very heavy, so that it hung perpendicularly and steadily. The middle of the 16th century saw the invention of the log-line. Voyages were, however, conducted rather by guesswork and experience, and especially so previous to the discovery of methods of finding the longitude. Mercator's system of plane charts furthered
progress; and Edward Wright discovered the true method of dividing the meridian, and drew up a table for the use of navigators by which latitude could be determined. The US global positioning system (GPS) was introduced 1992 and features 24 Navstar satellites that enable users to triangulate their position (from any three satellites) to within 15 m. In 1992, 85 nations agreed to take part in trials of a new navigation system which makes use of surplus military space technology left over from the Cold War. The new system, known as FANS or Future
Navigation System, makes use of the 24 Russian Glonass satellites and the 24 US GPS satellites. Small computers will gradually be fitted to civil aircraft to process the signals from the satellite, allowing aircraft to navigate with pinpoint accuracy anywhere in the world. The signals from at least three satellites will guide the craft to within a few metres of accuracy. FANS will be used in conjunction with four Inmarsat satellites to provide worldwide communications between pilots and air-traffic controllers. An Australian prototype for an electronic
navigation system ECDIS (Electronic Chart Display Information System) is a single computer-based apparatus that combines information from existing navigational aids, such as charts, radar, sonar and satellites. Research Navigation
Abbreviations
SciTech
Research Navigation