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The SEDRIS Data Representation Model
APPENDIX A - Classes Areal Feature |
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An instance of this DRM class specifies a <Primitive Feature> that encloses a bounded region, such as a forest or a built-up area.
Consider an <Areal Feature> representing a lake. It has a <Feature Face>, which defines its size, shape, and topological relationships; <Property Value> components that describe its characteristics, such as bottom composition, and a <Label> that identifies it as "Duck Lake".
No. Although in VPF, for example, the mere presence of Faces implies Level 3 topology, this is not the case in SEDRIS. <Areal Feature> instances may exist at any level of topology.
An <Areal Feature> can consist of multiple <Feature Face> instances. There is no requirement that the <Feature Face> instances be connected to one another.
For example, a forest that has a stream and a road passing through it commonly would be represented as a single <Areal Feature>, but might require multiple <Feature Face> instances.
An association between two <Feature Representation> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Geometry Hierarchy> instance and a <Feature Representation> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Property Grid> instance and a <Feature Representation> instance indicates that the environmental object(s) represented by the <Feature Representation> instance and the <Property Grid> instance (or some specific cell data within that <Property Grid> instance) have the semantic relationship indicated by the <Base Association Data> instance on the association relationship. Each associated <Property Grid> instance will indicate whether the entire <Property Grid> instance or only some specific cell data within it is participating in the relationship in question.
An association between two <Feature Representation> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Geometry Hierarchy> instance and a <Feature Representation> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Property Grid> instance and a <Feature Representation> instance indicates that the environmental object(s) represented by the <Feature Representation> instance and the <Property Grid> instance (or some specific cell data within that <Property Grid> instance) have the semantic relationship indicated by the <Base Association Data> instance on the association relationship. Each associated <Property Grid> instance will indicate whether the entire <Property Grid> instance or only some specific cell data within it is participating in the relationship in question.
These components support *attributes for derived objects*; that is, they are used only to specify texture mapping information for geometry that is derived from the <Primitive Feature> by the consumer. These <Image Mapping Function> components shall use <Image Anchor> components to specify the mapping.
This is needed because in many cases, a <Primitive Feature> may be significant only for a particular domain, such as radar.
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