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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It corresponds to Mapping Database, which includes all kinds of map datum. For rapidly searching map data at various scales, map data needs storing layeredly by "changing focuses".

数字地图包含着各种地图数据，为了在多种比例尺范围内能快速地检索地图数据，需要把地图数据分层存贮变焦。

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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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