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The SEDRIS Data Representation Model
APPENDIX A - Classes Perimeter Data |
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An instance of this DRM class specifies the perimeter of the region corresponding to the attributed object. The ordered <Location> components of a <Perimeter Data> instance specify the perimeter (outline) of the given region by specifying an implicit line between each pair of <Location> components i, i+1, with a last implicit line connecting the last <Location> component to the first <Location> component.
When a <Perimeter Data> instance is provided as a component of another object, the aggregate is the attributed object for which the perimeter is being specified. When a <Perimeter Data> instance is provided as a link object in a perimeter-related organization, the component object on the associated branch is the attributed object for which the perimeter is being specified.
Consider a thematic coverage in which the spatial extent forms a collection of tiles, where some of the tiles (due to shorelines) have irregular shapes. Consequently, this coverage is represented by a <Perimeter Related Features> organization, in which each tile's boundary can be correctly represented by a <Perimeter Data>.
Note that while a rectangular tile can be described by a <Perimeter Data> instance with 4 <Location> instances, an irregularly shaped tile may require a much larger number of <Location> instances.
Consider a polygonal representation of a region of terrain, organized into tiles based on political boundaries, such as different provinces within a country or different countries. Many of the tiles in this example have irregular shapes, so each tile is organized under a separate <Geometry Hierarchy> component of a < Perimeter Related Geometry>, with the corresponding <Perimeter Data> describing the boundary of that tile.
See also < Perimeter Related Geometry>.
The <Locations> defining the perimeter of the region, all of which shall be distinct.
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