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1 CHAPTER 1 INTRODUCTION TO MARINE NAVIGATION DEFINITIONS 100. The Art And Science Of Navigation Marine navigation blends both science and art. A good navigator gathers information from every available source, evaluates this information, determines a fix, and compares that fix with his pre-determined “dead reckoning” position. A navigator constantly evaluates the ship’s position, antic- ipates dangerous situations well before they arise, and always keeps “ahead of the vessel.” The modern navigator must also understand the basic concepts of the many navi- gation systems used today, evaluate their output’s accuracy, and arrive at the best possible navigational decisions. Navigation methods and techniques vary with the type of vessel, the conditions, and the navigator’s experience. Navigating a pleasure craft, for example, differs from nav- igating a container ship. Both differ from navigating a naval vessel. The navigator uses the methods and techniques best suited to the vessel and conditions at hand. Some important elements of successful navigation can- not be acquired from any book or instructor. The science of navigation can be taught, but the art of navigation must be developed from experience. 101. Types Of Navigation Methods of navigation have changed through history. Each new method has enhanced the mariner’s ability to complete his voyage safely and expeditiously. One of the most important judgments the navigator must make in- volves choosing the best method to use. Commonly recognized types of navigation are listed below. Dead reckoning (DR) determines position by ad- vancing a known position for courses and distances. A position so determined is called a dead reckoning (DR) position. It is generally accepted that only course and speed determine the DR position. Cor- recting the DR position for leeway, current effects, and steering error result in an estimated position (EP) . An inertial navigator develops an extremely accurate EP. Piloting involves navigating in restricted waters with frequent determination of position relative to geographic and hydrographic features. Celestial navigation involves reducing celestial measurements to lines of position using tables, spherical trigonometry, and almanacs. It is used pri- marily as a backup to satellite and other electronic systems in the open ocean. Radio navigation uses radio waves to determine po- sition by either radio direction finding systems or hyperbolic systems. Radar navigation uses radar to determine the dis- tance from or bearing of objects whose position is known. This process is separate from radar’s use as a collision avoidance system. Satellite navigation uses artificial earth satellites for determination of position. Electronic integrated bridge concepts are driving fu-
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