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The SEDRIS Data Representation Model
APPENDIX A - Classes Point Feature |
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An instance of this DRM class specifies a <Primitive Feature> for which the spatial information needed for the representation can be abstracted to a single topologically significant location. This is sometimes referred to as a "zero-dimensional" location, since the topology associated with a <Point Feature> does not provide length, width, or height information.
Consider a well represented a <Point Feature>. The <Point Feature> has a <Classification Data> classifying it as a well, an associated <Feature Node> specifying its location, and <Property Value> components specifying its depth below the terrain surface and the potability of the water it contains.
Consider a road interchange represented as a <Point Feature>. The <Point Feature> has a <Classification Data> classifying it as ECC_ROAD_INTERCHANGE, and an associated <Feature Node> specifying its location. In addition, the <Feature Node> in this example is associated with some <Feature Edge> instances that are part of the topology of some <Linear Feature> instances representing the roads in question.
Consider a small building represented as a <Point Feature>. It has a <Feature Node> that defines its location, <Classification Data> that identifies it as a building, and a set of <Property Value> components that describe its characteristics, such as its height and its building functional category.
No. A <Point Feature> shall consist of only a single <Feature Node>.
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.
The <Feature Node> associated with a <Point Feature> instance represents the topology of that <Point Feature>.
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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