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Navigational instruments refers to the instruments used by nautical navigators and pilots as tools of their trade. The purpose of navigation is to ascertain the present position and to determine the speed, direction etc. to arrive at the port or point of destination. ==Charts and drafting instruments== *Charts are maps of the areas to be navigated with details specific to the marine environment. *Computing aids: used in the necessary mathematical calculations. Today electronic computers or calculators are used. Other traditional aids used included tables (trigonometric, logarithms, etc.) and slide rules. *Dividers used for measuring lengths of lines and approximate lengths of non-linear paths on a chart. *Nautical almanac used to determine the position in the sky of a celestial body after a sight has been taken. *Parallel rules used for transferring a line to a parallel position. Also used to compare the orientation of a line to a magnetic or geographic orientation on a compass rose. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Navigational instrument」の詳細全文を読む スポンサード リンク
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