How ISO Does It[edit | edit source]
ISO 19115 combines spatial and temporal extents into a single object, called an EX_Extent, that includes temporal, vertical, and geographic extents.
The temporal and vertical extents are simple descriptions of temporal or vertical ranges.
The geographic extent can be described in three ways: The first option is a simple bounding box which works quite well in some simple situations. This is similar to the bounding box in the FGDC Metadata Standard, except that the FGDC box described the spatial extent of the entire dataset and this Extent object gives the spatial extent of a specific quality report.
The second option generalizes the bounding box to a bounding polygon. This covers a large number of cases which might involve natural shapes, such as watersheds, or political shapes, like county forecast zones, rather than rectangles. In the FGDC Standard this is similar to the G-Ring option for the spatial extent, except that it applies only to a specific quality report.
The final option allows specification of an identifier of a geographic region. This identifier includes a namespace and a name and allows the use of named spatial objects, like counties, to describe spatial extents. This is similar to the spatial keyword element of the FGDC Metadata Standard.