IfcSite

Item	Change	Description
IFC2x3 to IFC4
IfcSite
OwnerHistory	MODIFIED	Instantiation changed to OPTIONAL.
CompositionType	MODIFIED	Instantiation changed to OPTIONAL.

Semantic definitions at the entity

Entity definition

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 163 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 163 — Site composition

Figure 164 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 164 — Site elevations

HISTORY New entity in IFC1.0.

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
10	RefLatitude	IfcCompoundPlaneAngleMeasure	[0:1]	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. NOTE 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.	X
11	RefLongitude	IfcCompoundPlaneAngleMeasure	[0:1]	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. NOTE 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).	X
12	RefElevation	IfcLengthMeasure	[0:1]	Datum elevation relative to sea level.	X
13	LandTitleNumber	IfcLabel	[0:1]	The land title number (designation of the site within a regional system).	X
14	SiteAddress	IfcPostalAddress	[0:1]	Address given to the site for postal purposes.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE only the last modification in stored - either as addition, deletion or modification.	X
3	Name	IfcLabel	[0:1]	Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.	X
4	Description	IfcText	[0:1]	Optional description, provided for exchanging informative comments.	X
IfcObjectDefinition
	HasAssignments	IfcRelAssigns @RelatedObjects	S[0:?]	Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.	X
	Nests	IfcRelNests @RelatedObjects	S[0:1]	References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical strutures only).
	IsNestedBy	IfcRelNests @RelatingObject	S[0:?]	References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types).	X
	HasContext	IfcRelDeclares @RelatedDefinitions	S[0:1]	References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object.
	IsDecomposedBy	IfcRelAggregates @RelatingObject	S[0:?]	References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definitions can be aggregated by several other objects (occurrences or parts).	X
	Decomposes	IfcRelAggregates @RelatedObjects	S[0:1]	References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definitions can only be part of a single decomposition (to allow hierarchical strutures only).	X
	HasAssociations	IfcRelAssociates @RelatedObjects	S[0:?]	Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification.	X
IfcObject
5	ObjectType	-		This attribute is out of scope for this model view definition and shall not be set.
	IsTypedBy	IfcRelDefinesByType @RelatedObjects	S[0:1]	Set of relationships to the object type that provides the type definitions for this object occurrence. The then associated IfcTypeObject, or its subtypes, contains the specific information (or type, or style), that is common to all instances of IfcObject, or its subtypes, referring to the same type.	X
	IsDefinedBy	IfcRelDefinesByProperties @RelatedObjects	S[0:?]	Set of relationships to property set definitions attached to this object. Those statically or dynamically defined properties contain alphanumeric information content that further defines the object.	X
IfcProduct
6	ObjectPlacement	IfcObjectPlacement	[0:1]	Placement of the product in space, the placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system.	X
7	Representation	IfcProductRepresentation	[0:1]	Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement.	X
	ReferencedBy	IfcRelAssignsToProduct @RelatingProduct	S[0:?]	Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.	X
IfcSpatialElement
8	LongName	IfcLabel	[0:1]	Long name for a spatial structure element, used for informal purposes. It should be used, if available, in conjunction with the inherited Name attribute. NOTE In many scenarios the Name attribute refers to the short name or number of a spacial element, and the LongName refers to the full descriptive name.	X
	ContainsElements	IfcRelContainedInSpatialStructure @RelatingStructure	S[0:?]	Set of spatial containment relationships, that holds those elements, which are contained within this element of the project spatial structure. NOTE The spatial containment relationship, established by IfcRelContainedInSpatialStructure, is required to be an hierarchical relationship, where each element can only be assigned to 0 or 1 spatial structure element.	X
IfcSpatialStructureElement
9	CompositionType	IfcElementCompositionEnum	[0:1]	Denotes, whether the predefined spatial structure element represents itself, or an aggregate (complex) or a part (part). The interpretation is given separately for each subtype of spatial structure element. If no CompositionType is asserted, the dafault value 'ELEMENT' applies.	X
IfcSite
10	RefLatitude	IfcCompoundPlaneAngleMeasure	[0:1]	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. NOTE 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.	X
11	RefLongitude	IfcCompoundPlaneAngleMeasure	[0:1]	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. NOTE 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).	X
12	RefElevation	IfcLengthMeasure	[0:1]	Datum elevation relative to sea level.	X
13	LandTitleNumber	IfcLabel	[0:1]	The land title number (designation of the site within a regional system).	X
14	SiteAddress	IfcPostalAddress	[0:1]	Address given to the site for postal purposes.	X

Definitions applying to Bridge View

Instance diagram

Concept usage

Site Attributes

The Site Attributes concept applies to this entity.

Exchange
Import		O
Export		O

Spatial Container

The Spatial Container concept applies to this entity as shown in Table 19.

Type	Description
IfcElement	The site may contain elements directly (if those are not assigned to the individual building, building stories or spaces

Table 19 — IfcSite Spatial Container

Exchange
Import		R
Export		R

FootPrint GeomSet PolyCurve Geometry

The FootPrint GeomSet PolyCurve Geometry concept applies to this entity.

Product Local Placement

The Product Local Placement concept applies to this entity.

Spatial Decomposition

The Spatial Decomposition concept applies to this entity.

Exchange
Import		R
Export		R

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Bridge View
	User Identity	Bridge View
	Object Ownership	Bridge View
IfcObject
	Property Sets for Objects	Bridge View
IfcSite
	Site Attributes	Bridge View
	Spatial Container	Bridge View
	FootPrint GeomSet PolyCurve Geometry	Bridge View
	Product Local Placement	Bridge View
	Spatial Decomposition	Bridge View

Formal representations

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:sequence>

     <xs:element name="SiteAddress" type="ifc:IfcPostalAddress" nillable="true" minOccurs="0"/>

    </xs:sequence>

    <xs:attribute name="RefLatitude" type="ifc:List-IfcCompoundPlaneAngleMeasure" use="optional"/>

    <xs:attribute name="RefLongitude" type="ifc:List-IfcCompoundPlaneAngleMeasure" use="optional"/>

    <xs:attribute name="RefElevation" type="ifc:IfcLengthMeasure" use="optional"/>

    <xs:attribute name="LandTitleNumber" type="ifc:IfcLabel" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcSite

 SUBTYPE OF (IfcSpatialStructureElement);

  RefLatitude : OPTIONAL IfcCompoundPlaneAngleMeasure;

  RefLongitude : OPTIONAL IfcCompoundPlaneAngleMeasure;

  RefElevation : OPTIONAL IfcLengthMeasure;

  LandTitleNumber : OPTIONAL IfcLabel;

  SiteAddress : OPTIONAL IfcPostalAddress;

END_ENTITY;

 EXPRESS-G diagram

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