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This title, along with an elaborate explanation for using the projection that appears as a section of text on the map, shows that Mercator understood exactly what he had achieved and that he intended the projection to aid navigation. Mercator titled the map Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendata: "A new and augmented description of Earth corrected for the use of sailors". In 1569, Gerhard Kremer, known by his trade name Gerardus Mercator, announced a new projection by publishing a large planispheric map measuring 202 by 124 cm (80 by 49 in) and printed in eighteen separate sheets. If these sheets were brought to the same scale and assembled, they would approximate the Mercator projection. In 1537, he proposed constructing a nautical atlas composed of several large-scale sheets in the cylindrical equidistant projection as a way to minimize distortion of directions. Portuguese mathematician and cosmographer Pedro Nunes first described the mathematical principle of the loxodrome and its use in marine navigation.
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The projection in use was the equirectangular projection. However, this was a simple, and common, case of misidentification.
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Joseph Needham, a historian of China, wrote that the Chinese developed the Mercator projection hundreds of years before Mercator did, using it in star charts during the Song Dynasty. Snyder amends his assessment to "a similar projection" in 1994. However, given the geometry of a sundial, these maps may well have been based on the similar central cylindrical projection, a limiting case of the gnomonic projection, which is the basis for a sundial. The projection found on these maps, dating to 1511, was stated by Snyder in 1987 to be the same projection as Mercator's.
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German polymath Erhard Etzlaub engraved miniature "compass maps" (about 10×8 cm) of Europe and parts of Africa that spanned latitudes 0°–67° to allow adjustment of his portable pocket-size sundials. There is some controversy over the origins of the Mercator. 5.3 Mercator projection transformations.