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What is Navigation?
Navigation is the process of directing the movement of a craft from one point to another.
The term is derived from the Latin words navis meaning "ship" and agere meaning "to move" or "to direct".
The expression marine navigation is often used when the craft is a water-borne vessel, and air navigation when aircraft are involved. The expression space navigation is applied to navigation of craft operating outside the atmosphere of the earth.
Navigation is often considered to be both a science and an art. Science is involved in the development of the instruments and methods of navigation, as well as in the computations involved. The skillful use of navigational instruments, and the interpretation of available data, may be considered an art. This combination has led some authors to refer to navigation as a "scientific art".
The subject can be covered only in its broadest outlines in an article of this kind. For a fuller and more technical treatment the reader is referred to a good textbook such as Dutton's Navigation and Piloting, used at the United States Naval Academy, or the more comprehensive reference book American Practical Navigator (U.S. Navy Hydrographic Office, Publication No.9), originally by Nathaniel Bowditch.
Navigation may be conveniently discussed under three general headings: piloting, dead reckoning, and celestial navigation.
Piloting relates to the determination of position relative to the objects used. Traditionally, these have been natural landmarks and such manmade aids as lighthouses, lightships, beacons, and buoys. More recently, various electronic aids have been added. In space navigation, even celestial bodies might be used when position is determined relative to them.
Dead reckoning is the determination of position by advancing a well-determined position for the direction and distance that a craft is assumed to have traveled by a given time.
Celestial navigation is the determination of position by observation of celestial bodies, but not position relative to the bodies observed. On the earth, position by celestial navigation is determined by means of lines of position relative to the "geographical positions" (on earth) of the celestial bodies at the time of observation. The expression navigational astronomy is used to refer to that part of astronomy of direct use to a navigator, comprising principally celestial coordinates, time, and the apparent motions of celestial bodies.
History of Navigation
Navigation has been used ever since man ventured from his immediate surroundings with a definite destination in mind. Since natural landmarks were his first aids, piloting was the earliest form 'of navigation. This was still true when he set out upon the waters. Once he ventured out of sight of land, a crude form of dead reckoning came into use. Before instruments were developed, man read directions in the winds, water, and clouds. Celestial bodies were also used, but it was much later that they became useful for determination of position. This awaited accurate predictions of their future positions, and the development of instruments for measurement of angles in the sky. Distance, determined by estimate, was of less importance.