5.4.3.25 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:

• COMPLEX = site complex
• ELEMENT = site
• PARTIAL = site section

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 94 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 94 — Site composition

HISTORY  New entity in IFC1.0.

Attribute Use Definition

Figure 95 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.

• 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 95 — Site elevations

Plumbing System Design

 Instance diagram

The Identity concept applies to this entity.

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

The Site Location concept applies to this entity.

Exchange
Import									-
Export	O	O		O	O	O	O	O	-		O	O	R

The Spatial Decomposition concept applies to this entity as shown in Table 20.

Spatial Parts IfcBuilding

Table 20 — IfcSite Spatial Decomposition

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

Footprint Geometry

The Footprint Geometry concept applies to this entity as shown in Table 21.

RepresentationType Geometry GeometricCurveSet IfcGeometricCurveSet Annotation2D IfcAnnotationFillArea

Table 21 — IfcSite Footprint Geometry

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:

• IfcShapeRepresentation.RepresentationIdentifier = 'FootPrint'
• IfcShapeRepresentation.RepresentationType = 'GeometricCurveSet', or 'Annotation2D'

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

XSD Specification:

EXPRESS Specification:

Attribute Definitions:

Inheritance Graph:

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