Maps (on paper or on the screen) are flat surfaces; they require a transformation from the curved surface of the earth to the flat plane: a map projection.
纸上或屏幕上的地图是平面的；它们需要从地球的曲面向平面进行转换：地图投影。
2
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。
3
A sphere cannot be represented on a flat plane without distortion, which means all map projections distort in one way or another.