OpenLayers does not have the ability to re-project data itself, so all data included in a map must also be provided in Spherical Mercator projection.

OpenLayers本身并不具备重新投影数据的能力，所以包含在地图内的所有数据必须在Spherical Mercator投影内提供。

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Map projection 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 Mercator projection.

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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The map you're used to seeing pinned on classroom walls and in Atlases is known as a Mercator projection, and was first presented by the Flemish geographer Gerardus Mercator back in 1569.

过去常被钉在教室墙上而且常出现在地图册中的那幅地图以墨卡托投影著称，最早是由弗兰德地理学家杰拉杜斯·麦卡托提出来的，可追溯至1569年。

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Cumulatively, these resulted in the famous projection map of Gerardus Mercator in 1569, a plan of the world that still forms the basis of schoolroom teaching and Google Maps.

WSJ: Lost in Our Maps: A History of Cartographic Catastrophes