Craig retroazimuthal projection
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The Craig retroazimuthal
map projection In cartography, map projection is the term used to describe a broad set of transformations employed to represent the two-dimensional curved surface of a globe on a plane. In a map projection, coordinates, often expressed as latitude and longitud ...
was created by James Ireland Craig in 1909. It is a modified
cylindrical projection In cartography, map projection is the term used to describe a broad set of transformations employed to represent the two-dimensional curved surface of a globe on a plane. In a map projection, coordinates, often expressed as latitude and longitu ...
. As a retroazimuthal projection, it preserves directions from everywhere to one location of interest that is configured during construction of the projection. The projection is sometimes known as the
Mecca Mecca (; officially Makkah al-Mukarramah, commonly shortened to Makkah ()) is a city and administrative center of the Mecca Province of Saudi Arabia, and the Holiest sites in Islam, holiest city in Islam. It is inland from Jeddah on the Red ...
projection because Craig, who had worked in
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
as a
cartographer Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an im ...
, created it to help
Muslims Muslims ( ar, المسلمون, , ) are people who adhere to Islam, a monotheistic religion belonging to the Abrahamic tradition. They consider the Quran, the foundational religious text of Islam, to be the verbatim word of the God of Abraha ...
find their
qibla The qibla ( ar, قِبْلَة, links=no, lit=direction, translit=qiblah) is the direction towards the Kaaba in the Sacred Mosque in Mecca, which is used by Muslims in various religious contexts, particularly the direction of prayer for the s ...
. In such maps, Mecca is the configurable location of interest. Given latitude ''φ'' to plot, latitude ''φ'' of the fixed location of interest, longitude ''λ'' to plot, and the longitude ''λ'' of the fixed location of interest, the projection is defined by: :\begin x &= \lambda - \lambda_0\\ y &= \frac\Big(\sin \varphi \cos \left(\lambda - \lambda_0\right) - \tan \varphi_0 \cos \varphi\Big)\end But when ''λ'' − ''λ'' = 0, ''y'' above is undefined, so instead use the ratio's
continuous Continuity or continuous may refer to: Mathematics * Continuity (mathematics), the opposing concept to discreteness; common examples include ** Continuous probability distribution or random variable in probability and statistics ** Continuous ...
completion: :y = \sin \varphi \cos \left(\lambda - \lambda_0\right) - \tan \varphi_0 \cos \varphi = \sin \varphi - \tan \varphi_0 \cos \varphi


See also

*
List of map projections This is a summary of map projections that have articles of their own on Wikipedia or that are otherwise notable Notability is the property of being worthy of notice, having fame, or being considered to be of a high degree of interest, signif ...
* Hammer retroazimuthal projection


References


Further reading

*


External links


An interactive Java Applet to study the metric deformations of the Craig Projection


{{Map projections Map projections Salah