Conversion from one datum to another requires specialized algorithms and trained users, and is not supported by the Spatial Extender.
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。
Spatial index plays an important role in the organization and searching of datum for GIS. People searching spatial index have proposed many algorithms of it.
空间索引在GIS数据的组织和检索中具有重要的作用，研究者对空间索引技术进行了广泛的研究，提出了许多索引算法。
The realtime datum, spatial topological datum, datum of facility property, and the function of operating the datum are enveloped in class of spatial entity, and then set up object of spatial entity.
将实时数据、空间拓扑数据、设备属性数据以及对这些数据操作的函数封装为空间实体类，建立了空间实体对象。
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