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The SEDRIS Data Representation Model
APPENDIX A - Classes Primitive Feature |
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A <Feature> that is not hierarchically structured.
See individual subclasses for examples.
This is primarily determined by the dimensions of the <Feature>, in conjunction with the nature of the <Feature>, the resolution of the source imagery from which the feature was extracted, and the intended use of the extracted feature data. A long, narrow feature will be extracted as a <Linear Feature>, representing the centreline of the actual feature, with a width field. A very small feature will be extracted as a <Point Feature>, with length and width fields, or possibly a radius field.
An association between two <Feature> instances indicates that they are alternate representations of the same environmental object.
An association between a <Geometry Hierarchy> instance and a <Feature> instance indicates that the <Geometry Hierarchy> and the <Feature> are alternate representations of the same environmental object.
An association between a <Property Grid> instance and a <Feature> instance indicates that the <Feature> and the <Property Grid> (or some specific cell data within that <Property Grid>) are alternate representations of the same environmental object. Each associated <Property Grid> will indicate which is the case.
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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