5.4.3.12 IfcSite

Site
Grundstück

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, retrofit or turn down building(s), or for other construction related developments.

NOTE  Term according to ISO6707-1 vocabulary "area of land or water where construction work or other development is undertaken".

A site 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:

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).

Figure 32 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.
IfcSite as part of a spatial structure

Figure 32 — Site composition
HISTORY  New entity in IFC1.0.

Attribute Use Definition

Figure 33 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 (or referencing to any other geographic coordinate system other than WSG84) the entities IfcCoordinateReferenceSystem and IfcMapConversion have to be used to define an exact mapping of the project engineering coordinate system to the geographic (or map) coordinate system.

building heights 

Figure 33 — Site elevations

Construction Operations

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.

 Instance diagram

Identity

The Identity concept applies to this entity.

Exchange
Import R R R R R R R R R R R R R R R R R R R R R R R R R R R R
Export R R R R R R R R R R R R R R R R R R R R R R R R R R R R


Spatial Composition

The Spatial Composition concept applies to this entity as shown in Table 29.
Spatial CompositeDescription
 A site is contained in a project, where COBie requires a project to contain a single site.

Table 29 — IfcSite Spatial Composition

Exchange
Import R R R R R R R R R R R R R R R R R R R R R R R R R R R R
Export R R R R R R R R R R R R R R R R R R R R R R R R R R R R


Revision Control

The Revision Control concept applies to this entity.

Exchange
Import O O O O O O O O O O O O O O O O O O O O O O O O O O O O
Export O O O O O O O O O O O O O O O O O O O O O O O O O O O O


XSD Specification:

 <xs:element name="IfcSite" type="ifc:IfcSite" substitutionGroup="ifc:IfcSpatialStructureElement" nillable="true"/>
 <xs:complexType name="IfcSite">
  <xs:complexContent>
   <xs:extension base="ifc:IfcSpatialStructureElement"/>
  </xs:complexContent>
 </xs:complexType>

EXPRESS Specification:

ENTITY IfcSite
SUBTYPE OF (IfcSpatialStructureElement);
RefLatitude : OPTIONAL IfcStrippedOptional;
RefLongitude : OPTIONAL IfcStrippedOptional;
RefElevation : OPTIONAL IfcStrippedOptional;
LandTitleNumber : OPTIONAL IfcStrippedOptional;
SiteAddress : OPTIONAL IfcStrippedOptional;
END_ENTITY;

Attribute Definitions:

RefElevation : Datum elevation relative to sea level.
LandTitleNumber : The land title number (designation of the site within a regional system).
SiteAddress : Address given to the site for postal purposes.

Inheritance Graph:

ENTITY IfcSite
ENTITY IfcRoot
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
INVERSE
HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcObject
ObjectType : OPTIONAL IfcStrippedOptional;
INVERSE
IsTypedBy : SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy : SET OF IfcRelDefinesByProperties FOR RelatedObjects;
ENTITY IfcProduct
ObjectPlacement : OPTIONAL IfcStrippedOptional;
Representation : OPTIONAL IfcStrippedOptional;
INVERSE
ENTITY IfcSpatialElement
LongName : OPTIONAL IfcStrippedOptional;
INVERSE
ContainsElements : SET OF IfcRelContainedInSpatialStructure FOR RelatingStructure;
ENTITY IfcSpatialStructureElement
CompositionType : OPTIONAL IfcStrippedOptional;
ENTITY IfcSite
RefLatitude : OPTIONAL IfcStrippedOptional;
RefLongitude : OPTIONAL IfcStrippedOptional;
RefElevation : OPTIONAL IfcStrippedOptional;
LandTitleNumber : OPTIONAL IfcStrippedOptional;
SiteAddress : OPTIONAL IfcStrippedOptional;
END_ENTITY;

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