Defined in File Ifc4.h
IfcSite: public Ifc4::IfcSpatialStructureElement¶
Definition from ISO 6707-1:1989: Area where construction works are undertaken. A site is a defined area of land, possibly covered with water, on which the project construction is to be completed. A site may be used to erect building(s) or other AEC products. A site (IfcSite) may include a definition of the single geographic reference point for this site (global position using WGS84 with Longitude, Latitude and Elevation). The precision is provided up to millionth of a second and it provides an absolute placement in relation to the real world as used in exchange with geospational information systems. If asserted, the Longitude, Latitude and Elevation establish the point in WGS84 where the point 0.,0.,0. of the LocalPlacement of IfcSite is situated. The geometrical placement of the site, defined by the IfcLocalPlacement, shall be always relative to the spatial structure element, in which this site is included, or absolute, i.e. to the world coordinate system, as established by the geometric representation context of the project. The world coordinate system, established at the IfcProject.RepresentationContexts, may include a definition of the true north within the XY plane of the world coordinate system, if provided, it can be obtained at IfcGeometricRepresentationContext.TrueNorth. A project may span over several connected or disconnected sites. Therefore site complex provides for a collection of sites included in a project. A site can also be decomposed in parts, where each part defines a site section. This is defined by the composition type attribute of the supertype IfcSpatialStructureElements which is interpreted as follow:
COMPLEX = site complex ELEMENT = site PARTIAL = site section
HISTORY New entity in IFC Release 1.0.
Property Set Use Definition The property sets relating to the IfcSite are defined by the IfcPropertySet and attached by the IfcRelDefinesByProperties relationship. It is accessible by the inverse IsDefinedBy relationship. The following property set definitions specific to the IfcSite are part of this IFC release:
Pset_SiteCommon: common property set for all types of site
Quantity Use Definition The quantities relating to the IfcSite are defined by the IfcElementQuantity and attached by the IfcRelDefinesByProperties relationship. It is accessible by the inverse IsDefinedBy relationship. The following base quantities are defined and should be exchanged with the IfcElementQuantity.Name = ‘BaseQuantities’. Other quantities, being subjected to local standard of measurement, can be defined with another string value assigned to Name. In this case a valid value for MethodOfMeasurement has to be provided.
Qto_SiteBaseQuantities: base quantities for all site occurrences.
Spatial Structure Use Definition The IfcSite is used to build the spatial structure of a building (that serves as the primary project breakdown and is required to be hierarchical). The spatial structure elements are linked together by using the objectified relationship IfcRelAggregates. The IfcSite references them by its inverse relationships:
IfcSite.Decomposes referencing (IfcProject || IfcSite) by IfcRelAggregates.RelatingObject, If it refers to another instance of IfcSite, the referenced IfcSite needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcSite has ELEMENT), or ELEMENT (if the other IfcSite has PARTIAL). IfcSite.IsDecomposedBy referencing (IfcSite || IfcBuilding || IfcSpace) by IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcSite, the referenced IfcSite needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcSite has COMPLEX), or PARTIAL (if the other IfcSite has ELEMENT).
If there are building elements and/or other elements directly related to the IfcSite (like a fence, or a shear wall), they are associated with the IfcSite by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcIfcSite references them by its inverse relationship:
Figure 51 shows the IfcSite as part of the spatial structure. In addition to the logical spatial structure, also the placement hierarchy is shown. In this example the spatial structure hierarchy and the placement hierarchy are identical. NOTE Detailed requirements on mandatory element containment and placement structure relationships are given in view definitions and implementer agreements.
Figure 51 — Site composition
Attribute Use Definition Figure 52 describes the heights and elevations of the IfcSite. It is used to provide the geographic longitude, latitude, and height above sea level for the origin of the site. The origin of the site is the local placement. The provision of longitude, latitude, height at the IfcSite for georeferencing is provided for upward compatibility reasons. It requires a single instance of IfcSite and WGS84 as coordinate reference system. For exact georeferencing the new entities IfcCoordinateReferenceSystem and IfcMapConversion should be used.
reference height of site is provided by: IfcSite.RefElevation, it is given according to the height datum used at this location. the reference height of each building situated at the site is given againt the same height datum used at this location. the elevations of each storey belonging to each building are given as local height relative to the reference height of the building.
Figure 52 — Site elevations
Geometry Use Definitions The geometric representation of IfcSite is given by the IfcProductDefinitionShape and IfcLocalPlacement allowing multiple geometric representations. Local placement The local placement for IfcSite is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.
The PlacementRelTo relationship of IfcLocalPlacement shall point to the IfcSpatialStructureElement of type “IfcSite”, if relative placement is used (e.g. to position a site relative a a site complex, or a site section to a site). If the relative placement is not used, the absolute placement is defined within the world coordinate system. If there is only one site object, then this is the default situation.
Foot Print Representation The foot print representation of IfcSite is given by either a single 2D curve (such as IfcPolyline or IfcCompositeCurve), or by a list of 2D curves (in case of inner boundaries). The representation identifier and type of this geometric representation of IfcSite is:
Survey Points Representation The survey point representation of IfcSite is defined using a set of survey points and optionally breaklines. The breaklines are restricted to only connect points given in the set of survey points. Breaklines, if given, are used to constrain the triangulation. The representation identifier and type of this geometric representation of IfcSite is:
Figure 53 shows a set of survey points, given as 3D Cartesian points within the object coordinate system of the site. Figure 54 shows the result after facetation. The set of IfcCartesianPoint is included in the set of IfcGeometricCurveSet.Elements.
Figure 53 — Site survey points Figure 54 — Site survey points facetation
Figure 55 shows A set of survey points, given as 3D Cartesian points, and a set of break points, given as a set of lines, connecting some survey points, within the object coordinate system of the site. Figure 56 shows the result after facetation. The set of IfcCartesianPoint and the set of IfcPolyline are included in the set of IfcGeometricCurveSet.Elements.
Figure 55 — Site breaklines Figure 56 — Site breaklines facetation
NOTE The geometric representation of the site has been based on the ARM level description of the site_shape_representation given within the ISO 10303-225 “Building Elements using explicit shape representation”.
Body Representation The body representation of IfcSite is defined using a solid or surface model. Applicable solids are the IfcFacetedBrep or on the IfcFacetedBrepWithVoids, applicable surface models are the IfcFaceBasedSurfaceModel and the IfcShellBasedSurfaceModel. The representation identifier and type of this representation of IfcSite is:
Whether the optional attribute RefLatitude is defined for this IfcSite.
World Latitude at reference point (most likely defined in legal description). Defined as integer values for degrees, minutes, seconds, and, optionally, millionths of seconds with respect to the world geodetic system WGS84. Latitudes are measured relative to the geodetic equator, north of the equator by positive values - from 0 till +90, south of the equator by negative values - from 0 till -90.
Whether the optional attribute RefLongitude is defined for this IfcSite.
World Longitude at reference point (most likely defined in legal description). Defined as integer values for degrees, minutes, seconds, and, optionally, millionths of seconds with respect to the world geodetic system WGS84. Longitudes are measured relative to the geodetic zero meridian, nominally the same as the Greenwich prime meridian: longitudes west of the zero meridian have negative values - from 0 till -180, longitudes east of the zero meridian have positive values - from 0 till -180. Example: Chicago Harbor Light has according to WGS84 a longitude -87.35.40 (or 87.35.40W) and a latitude 41.53.30 (or 41.53.30N).
Whether the optional attribute RefElevation is defined for this IfcSite.
Datum elevation relative to sea level.
Whether the optional attribute LandTitleNumber is defined for this IfcSite.
The land title number (designation of the site within a regional system).
Whether the optional attribute SiteAddress is defined for this IfcSite.
IfcSite(std::string v1_GlobalId, ::Ifc4::IfcOwnerHistory *v2_OwnerHistory, boost::optional<std::string> v3_Name, boost::optional<std::string> v4_Description, boost::optional<std::string> v5_ObjectType, ::Ifc4::IfcObjectPlacement *v6_ObjectPlacement, ::Ifc4::IfcProductRepresentation *v7_Representation, boost::optional<std::string> v8_LongName, boost::optional<::Ifc4::IfcElementCompositionEnum::Value> v9_CompositionType, boost::optional<std::vector<int>> v10_RefLatitude, boost::optional<std::vector<int>> v11_RefLongitude, boost::optional<double> v12_RefElevation, boost::optional<std::string> v13_LandTitleNumber, ::Ifc4::IfcPostalAddress *v14_SiteAddress)¶