Mapprojection in cartography is a way to present a two-dimensional curved surface on a plane, such as a normal map. Figure 2 shows a Traverse Mercatorprojection.
绘图法中的地图投影方法可以在平面中表示一个两维的曲面，例如一个标准地图。
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OpenLayers does not have the ability to re-project data itself, so all data included in a map must also be provided in Spherical Mercatorprojection.
The map you're used to seeing pinned on classroom walls and in Atlases is known as a Mercatorprojection, and was first presented by the Flemish geographer Gerardus Mercator back in 1569.