Broad sailing

Broad sailing to the Azores island of Terceira from Vigo : First the latitude Terceira (38.7 ° N) is sailed in known waters (for example along the coast) (point A), then you follow this latitude westwards until the island comes into view. To do this, the ship does not need to know the geographical longitude of the island or its current length, but the distance to the destination until visual contact is not exactly known.

As width Sailing (Engl. "Latitude sailing") refers to a method of navigation that a destination without precise knowledge of the geographical length along its latitude controls, exactly from the west or east.

The geographical latitude of the destination was previously taken from a table, as can be found in early navigation manuals (from around 1509: Regimento do astrolabio ). Then you first sailed to the latitude on which the destination was located, whereby you just had to know for sure whether you reached the latitude west or east of the destination. Accordingly, one followed him to the goal.

As long as the longitude problem, which was not solved until the middle of the 18th century, made an exact determination of the longitude impossible, latitude sailing was the only method of astronomical navigation. The current geographic latitude can be determined relatively easily by measuring the height of the North Star above the horizon.

This method was developed in Portugal during the 15th century on the occasion of the voyages of discovery along the West African coast.

Broad sailing was initially limited to the northern hemisphere of the earth, as the North Star, which is close to the (northern) celestial pole and used to determine latitude, remains below the horizon from the southern hemisphere. The southern celestial pole is not marked by any bright star. Only when more precise angle measuring instruments and tables of the sun declination were available, the latitude could also be determined in the southern hemisphere based on the position of the sun, so that latitude sailing was also possible there.

literature

• Luís de Albuquerque: Astronomical navigation , Lisboa 1988
• Hans-Christian Free Life: The Polar Star in Navigation , in: Sudhoffs Archive for the History of Medicine and Natural Sciences, vol. 39 (1955), pp. 157–161
• Hubert Michéa: Note concernant les procédés de navigation à latitude constante au XVI siècle , in: Études Canadiennes / Canadian Studies, Vol. 10 (1984), No. 17, pp. 225-230
• David Watkin Waters: Science and the techniques of navigation in the Renaissance , Greenwich 1976
• Wolfgang Köberer: Instrument unde Declinatie der Sünnen , the oldest Low German navigation manual by Jacob Alday from 1578, facsimile, transcritical and commentary volume , Edition Stiedenrod, Wiefelstede 2009

See also

Determination of latitude