Having a standard accurate datum set becomes increasingly important as multiple layers of
information about the same area are collected and analyzed. The layers are developed into
geographic information systems (GIS), which enable the relationships between layers of data to
be examined. In order to function effectively, a GIS must possess one essential attribute. It must
have the ability to geographically relate data within and across layers. For example, if a dataset
about vegetation is being examined against the data sets for topography and soils, the accurate
spatial compatibility of the two datasets is critical.