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.
数据库本身往往不包含关于大地基准点的信息，所以您必须从创建坐标的应用程序中查明大地基准点。
Usually, the database itself contains no information about its geodetic datum, so you must find this out from the application that created the coordinates.
数据库本身往往不包含关于大地基准点的信息，所以您必须从创建坐标的应用程序中查明大地基准点。 。
Usually, , the database itself contains no information about its geodetic datum, so you must findthis out from the application that created the coordinates.
从一种大地基准点转换到另一种需要专门的算法，而且要求用户受过训练，Spatial Extender不支持这种转换。
Conversion from one datum to another requires specialized algorithms and trained users, and is not supported by the Spatial Extender.
它常常是全球大地基准点（比如WGS-84，即World GeodeticSystem 1984，由所有GPS设备使用），或地区性大地基准点（比如NAD-83，即NorthAmericanDatum 1983）。
Often, it is something global like WGS-84 (World Geodetic System 1984, used by all GPS devices), or a regional datum like NAD-83 (North American Datum 1983).
它常常是全球大地基准点（比如WGS-84，即World GeodeticSystem 1984，由所有GPS设备使用），或地区性大地基准点（比如NAD-83，即NorthAmericanDatum 1983）。
Often, it is something global like WGS-84 (World Geodetic System 1984, used by all GPS devices), or a regional datum like NAD-83 (North American Datum 1983).
应用推荐