- Kamal
:"For the
Indian actor , seeKamal Hassan ."A kamal is acelestial navigation device that determineslatitude . The invention of the kamal allowed for the earliest known latitudesailing , and was thus the earliest step towards the use ofquantitative methods innavigation .The kamal originated from Arab navigators of the in the late 9th century, [Harv|McGrail|2004|pp=85-6] and employed in the
Indian Ocean from the 10th century.Harv|McGrail|2004|p=316] It was then adopted by Indian navigators soon after, [citation|title=Cultural Foundations of Mathematics: The Nature of Mathematical Proof and Transmission of the Calculus From India to Europe in the 16th c. CE|last=Raju|first=C. K.|year=2007|isbn=8131708713|pages=240-59|url=http://ckraju.net/IndianCalculus/Education/Kamal_pages.pdf|accessdate=2008-09-10] and then adopted by Chinese navigators some time before the 16th century.Harv|McGrail|2004|p=393]The kamal consists of a rectangular wooden ca about 2 inches by 1 inch (5 cm by 2.5 cm), to which a string with several equally spaced knots is attached through a hole in the middle of the card. The kamal is used by placing one end of the string in the teeth while the other end is held away from the body roughly parallel to the ground. The card is then moved along the string, positioned so the lower edge is even with the horizon, and the upper edge is occluding a target star, typically
Polaris because its angle to the horizon does not change with longitude or time. The angle can then be measured by counting the number of knots from the teeth to the card, or a particular knot can be tied into the string if travelling to a known latitude.The knots were typically tied to measure angles of one finger-width. When held at arm's length, the width of a finger measures an angle that remains fairly similar from person to person. This was widely used (and still is today) for rough angle measurements, an angle known as "issabah" in Arabic, or a "chih" in Chinese. By modern measure, this is about 1 degree, 36 minutes, and 25 seconds, or just over 1.5 degrees.
Due to the limited width of the card, the kamal was only really useful for measuring Polaris in equatorial latitudes, which perhaps explains why it was not common in Europe. For these higher-latitude needs somewhat more complex devices based on the same principle were used, notably the
cross-staff andbackstaff .The kamal is still a tool recommended for use in
sea kayak ing.Burch, David, "Fundamentals of Kayak Navigation", 2nd edition, The Globe Pequot Press, 1993, ISBN 1-56440-155-3] In such an application, it can be used for estimating distances to land.A similar, but unrelated device called the
touisse was used by the Aztecs to determine latitude.Notes
References
*Citation
last=McGrail
first=Sean
year=2004
title=Boats of the World
publisher=Oxford University Press
isbn=0199271860
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