CityFurniture ModelΒΆ

City furniture objects are immovable objects like lanterns, traffic lights, traffic signs, flower buckets, advertising columns, benches, delimitation stakes, or bus stops. The class CityFurniture may have the attributes class, function and usage (cf. UML-diagram in Fig. 2.13). Their possible values are explained in detail in the CityGML specification. The class attribute allows an object classification like traffic light, traffic sign, delimitation stake, or garbage can, and can occur only once. The function attribute describes, to which thematic area the city furniture object belongs to (e.g. transportation, traffic regulation, architecture etc.), and can occur multiple times. The attribute usage denotes the real purpose of the city object, and can occur multiple times as well.


Fig. 2.13 City furniture model

Since CityFurniture is a subclass of CityObject and hence is a feature, it inherits the attribute gml:name. As with any CityObject, CityFurniture objects may be assigned ExternalReferences and GenericAttributes. For ExternalReferences city furniture objects can have links to external thematic databases. Thereby, semantical information of the objects, which cannot be modelled in CityGML, can be transmitted and used in the 3D city model for further processing, for example information from systems of power lines or pipelines, traffic sign cadastre, or water resources for disaster management.

City furniture objects can be represented in city models with their specific geometry, but in most cases the same kind of object has an identical geometry. The geometry of CityFurniture objects in LoD 1-4 may be represented by an explicit geometry (lodXGeometry where X is between 1 and 4) or an ImplicitGeometry object (lodXImplicitRepresentation with X between 1 and 4). In the concept of ImplicitGeometry the geometry of a prototype city furniture object is stored only once in a local coordinate system and referenced by a number of features. Spatial information of city furniture objects can be taken from city maps or from public and private external information systems. In order to specify the exact intersection of the DTM with the 3D geometry of a city furniture object, the latter can have a TerrainIntersectionCurve (TIC) for each LoD. This allows for ensuring a smooth transition between the DTM and the city furniture object.