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Online version of Chart No.1 with "Symbols, Abbreviations and Terms" used in nautical charts; Portolan Chart of Gabriel de Vallseca, 1439; The short film "Reading Charts (April 6, 1999)" is available for free viewing and download at the Internet Archive. Nautical charts available online (Nautical Free) Online Nautical Charts Viewer
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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.
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.
Individual charts varied so much in form and interpretation that the individual navigator who made the chart was the only person who could fully interpret and use it. The use of stick charts ended after World War II when new electronic technologies made navigation more accessible and travel among islands by canoe lessened.
An example of a complete light characteristic is "Gp Oc(3) W 10s 15m 10M". This indicates that the light is a group occulting light in which a group of three eclipses repeat every 10 seconds; the light is white; the light is 15 metres above the chart datum and the nominal range is 10 nautical miles.
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.
Portolan charts are nautical charts, first made in the 13th century in the Mediterranean basin and later expanded to include other regions. The word portolan comes from the Italian portolano , meaning "related to ports or harbors ", and which since at least the 17th century designates "a collection of sailing directions".