Navigation can be defined as the science of finding one's way between 2 points. However, the term is now used most commonly in the context of aviation or marine travel, as in navigating an aircraft or navigating a ship across the ocean. Navigation requires establishing one's position and the measurement of motion relative to the Earth's surface. The development of this science is intimately connected with the history of man's efforts to travel the seas, which was in turn driven by the twin forces of world exploration and mercantile expansion.
Evidence suggests that the Phoenicians, Arabs and ancient Greeks were familiar with the use of nighttime positions of stars and constellations to aid in marine navigation, but this knowledge was lost to Europeans in the Dark Ages and only regained after about the year 1000 from the Arabs. Several native Pacific cultures also made use of these techniques. Until the reintroduction of this concept, navigation techniques used in Europe usually relied on staying within sight of land and using "Portolan charts" showing the shape of coastlines and the location of each harbour.
The translation of Ptolemy's Geography around 1409 began a revolution in navigation and introduced to Europe the concept of dividing the Earth's surface into a grid of east-west and north-south lines of latitude and longitude. The intersection of the latitude and longitude is the position of the vessel. Latitude, or north-south position, could be determined by using a sextant to measure the angle of a known star or the sun at its highest point above the horizon and referring to celestial tables developed by astronomers; but longitude (the east-west position) required knowledge of the time at which a star sighting was taken. This in turn spurred the development of accurate timepieces, or chronometers. Thus, the development of timekeeping, navigation, astronomy and mapmaking are all closely intertwined.
While celestial navigation is still taught to ships officers, modern aids to navigation are now relied upon extensively in both air and marine modes. For mariners, these range from satellite systems, such as the Global Positioning System (GPS), through radio position measuring systems such as "LORAN-C," still in extensive use in North America, to the more conventional aids, such as lighthouses, buoys and shore beacons. In Canada, aids to navigation are provided by the Canadian Coast Guard of the Department of Fisheries and Ocenas for the benefit of all types of users - from pleasure craft to large container ships. Air navigation aids are provided by Transport Canada.
Because of its long history, marine navigation normally has priority over other uses of the water, and approval for the construction of works which could obstruct marine navigation is also required from the Canadian Coast Guard.