这二者以及很多其他的商业的免费数据源都会使用球形的Mercator数据投影（由EuropeanPetroleumSurveyGroup [EPSG]code 900913 标识）。
These and many other commercial free data sources use the spherical Mercator data projection (identified by European Petroleum Survey Group [EPSG] code 900913).
地理和投影坐标系都包含对地球形状的假设(一个略扁的球体)；这称为大地基准点。
Both geographic and projected coordinate systems include a definition of the assumed shape of the earth (a flattened sphere); this is called the geodetic datum.
地理和投影坐标系都包含对地球形状的假设(一个略扁的球体)；这称为大地基准点。
Both geographic and projected coordinate systems include a definition of the assumed shape of the earth (a flattened sphere); this is called the geodetic datum.
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