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A nautical chart or hydrographic chart is a graphic representation of a sea region ... such as a ship's course or a compass reading to a landmark. On nautical charts, ...
A common compass rose as found on a nautical chart showing both true north (using a nautical star symbol) and magnetic north with magnetic variation. Also notice the correspondence between the 32-point rose (inner circle) and the modern 0–360° graduations. Compass rose with the eight principal winds.
Instruments used to plot a course on a nautical chart. In navigation, the course of a watercraft or aircraft is the cardinal direction in which the craft is to be steered.The course is to be distinguished from the heading, which is the direction where the watercraft's bow or the aircraft's nose is pointed.
Before the advent of nautical charts in the 14th century, navigation at sea relied on the accumulated knowledge of navigators and pilots.Plotting a course at sea required knowing the direction and distance between point A and point B. Knowledge of where places lay relative to each other was acquired by mariners during their long experience at sea.
If a navigator is west of the agonic line, then the variation is eastward; the Magnetic North Pole appears to the east of the Geographic North Pole. The farther the navigator is from the agonic line, the greater the variation. The local magnetic variation is indicated on NOAA nautical charts at the center of the compass rose. The magnetic ...
Navigation that follows a rhumb line — that is, all meridians are cut at the same angle. On a nautical chart following the Mercator projection, a loxodromic is represented by a straight line. This type of navigation is useful for not too long distances, as it allows the course to remain steady, [16] but it does not offer the shortest distance.
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.
The oldest sailing directions, dating back to the middle ages, descended directly from the Greek and Roman periplii: in classical times, in the absence of real nautical charts, navigation was carried out using books that described the coast, not necessarily intended for navigation, but more often consisting of reports of previous voyages, or celebrations of the deeds of leaders or rulers.