From GPS surveying the WGS-84 coordinates are acquired, while in reality coordinates in local coordinate system are needed, so conversion from WGS-84 coordinates to local coordinates is necessary.

• · GPS测量得到的是WGS-84坐标，而实用上需要的是地方坐标系坐标，因而得把WGS-84坐标转换地方坐标系坐标。