The remote sensing datum, map datum, photo datum, document datum, DEM, and meta-data are included in the database.

数据库包括地图数据、遥感影像数据、文档数据、照片数据、数字高程模型以及各类数据的元数据信息。

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One is how to get geography datum independently, i. e, how to get a map in a projection by using the datum gotten from a map in another projection.

这两个问题是，位置信息采集的重用或投影方式无关问题（即在某种地球投影地图上录取的地理位置信息可以按另一种地球投影投影或制作地图）；

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This paper approaches the reference datum of GPS and electronic map from concepts model, and analyses the basic relations of coordinate transformation.

从概念模型的角度探讨了GPS和电子地图的参考基准问题。

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