Modeling "Geometry"

[yarondassonneville]

During the webinar the project team presented its approach for modeling geometry for both building and building unit. At first glance, one could see that the idea is to have a data type instead of an entity.

Second, building unit would call a geometry data type and building a building geometry data type, which is more detailed and allows for 2D and 3D modeling.

The building geometry data allow for geometry coordinates and positioning through GML and WKT. It was requested that 2D and 3D geometry should be defined. 2D information should be seen as the footprint of a building. 3D information, depending on the level of detail, shows the volume with facades, roof, etc. More information can be found in the meeting report.

The building unit geometry data is made possible by added ‘basic’ geometry entities such as multicurve, points, etc. 3D information will not be foreseen for building units as this is possible via 3DGeometry LoD4 at building level.

While the working group agreed not to model 3D Geometry level of detail 3 and 4, it was requested to further look into the possibility of adding different space elements, e.g., doors, position of building units, windows. INSPIRE covers these elements thanks to 3D Geometry level of detail 3 and 4. Level of detail 3 is an accurate description of the exterior (including openings such as doors and windows) while level of detail 4 is an interior model.

Do you agree with the suggested approach to model 2D and 3G geometry for building (unit) and do you see any missing elements that should be modeled as part of 2D and 3D Geometry?

[GeertThijs]

The current model follows INSPRE which means:

• For Buildings: Dedicated datatypes for 2D and 3Dgeometry with for 2D geometry of type GM_Object and additional attributes eg to be able to specify the elevation of the Building or what kind of generalisation was applied (footprint? rooftop?). Remark: GM_Object allows for things like points, curves, polygons and... solids. And even the multi-versions of that. For 3D geometry there are the 4 levels which all can be represented with MultiSurfaces and/or MultiSolids. The ICEG model has no seperate application profiles, so both datatypes are provided in the same profile.
• For BuildingUnits: No dedicated datatypes. Which just means no additional attributes as there is no need eg for elevation (which differs from floor level!) or generalisation type (as a BuildingUnit as such has no footprints or rooftops). For geometry the 2D application profile of INSPRE uses GM_Primitive (= all GM_Geometry kinds apart from multigeometries). For 3D MultiSolid is available. As ICEG has no seperate application profiles for 2D and 3D we propose to use GM_Geometry instead (which would allow some extra types like multisurface).

[yarondassonneville]

Thank you for the clarification Geert. This is indeed the way it is modeled right now. Furthermore, in the current model, the datatype Geometry is the equivalent of GM_Object. This ensures that the datatypes within Geometry are also the equivalents of, for example, GM_MultiSurface and GM_Solid.

[bahimc]

As no additional feedback was received on whether to model LOD3 & 4, this won't be modelled, and the issue will be closed.