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 167 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 167 — Site composition

Figure 168 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 168 — Site elevations

HISTORY New entity in IFC1.0.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
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	C
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).	X
	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.	X
	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	IfcLabel	[0:1]	The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED.	X
	IsDeclaredBy	IfcRelDefinesByObject @RelatedObjects	S[0:1]	Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.	X
	Declares	IfcRelDefinesByObject @RelatingObject	S[0:?]	Link to the relationship object pointing to the reflected object(s) that receives the object definitions. The reflected object has to be part of an object occurrence decomposition. The associated IfcObject, or its subtypes, provides the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.	X
	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
	ServicedBySystems	IfcRelServicesBuildings @RelatedBuildings	S[0:?]	Set of relationships to systems, that provides a certain service to the spatial element for which it is defined. The relationship is handled by the objectified relationship IfcRelServicesBuildings.	X
	ReferencesElements	IfcRelReferencedInSpatialStructure @RelatingStructure	S[0:?]	Set of spatial reference relationships, that holds those elements, which are referenced, but not contained, within this element of the project spatial structure. NOTE The spatial reference relationship, established by IfcRelReferencedInSpatialStructure, is not required to be an hierarchical relationship, i.e. each element can be assigned to 0, 1 or many spatial structure elements. EXAMPLE A curtain wall maybe contained in the ground floor, but maybe referenced in all floors, it reaches. Ø\X	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 Common Use Definitions

Instance diagram

Concept usage

Spatial Composition

The Spatial Composition concept applies to this entity.

By using the inverse relationship IfcSite.Decomposes it references IfcProject || IfcSite through 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).

Spatial Decomposition

The Spatial Decomposition concept applies to this entity.

By using the inverse relationship IfcSite.IsDecomposedBy it references (em>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).

Spatial Container

The Spatial Container concept applies to this entity.

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:

IfcSite.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 64.

PredefinedType

Name

Properties

Pset_LandRegistration

Single Value

Name	Value
LandID	IfcIdentifier
IsPermanentID	IfcBoolean
LandTitleID	IfcIdentifier

Pset_SiteCommon

Single Value

Name	Value
Reference	IfcIdentifier
BuildableArea	IfcAreaMeasure
SiteCoverageRatio	IfcPositiveRatioMeasure
FloorAreaRatio	IfcPositiveRatioMeasure
BuildingHeightLimit	IfcPositiveLengthMeasure
TotalArea	IfcAreaMeasure

Pset_PropertyAgreement

Single Value

Name	Value
Identifier	IfcIdentifier
Version	IfcLabel
VersionDate	IfcDate
PropertyName	IfcLabel
CommencementDate	IfcDate
TerminationDate	IfcDate
Duration	IfcDuration
Options	IfcText
ConditionCommencement	IfcText
Restrictions	IfcText
ConditionTermination	IfcText

Enumerated Value

Name	Value	Value
AgreementType	IfcLabel	IfcLabel

Pset_ThermalLoadAggregate

Single Value

Name	Value
TotalCoolingLoad	IfcPowerMeasure
TotalHeatingLoad	IfcPowerMeasure
LightingDiversity	IfcPositiveRatioMeasure
InfiltrationDiversitySummer	IfcPositiveRatioMeasure
InfiltrationDiversityWinter	IfcPositiveRatioMeasure
ApplianceDiversity	IfcPositiveRatioMeasure
LoadSafetyFactor	IfcPositiveRatioMeasure

Pset_ThermalLoadDesignCriteria

Single Value

Name	Value
OccupancyDiversity	IfcPositiveRatioMeasure
OutsideAirPerPerson	IfcVolumetricFlowRateMeasure
ReceptacleLoadIntensity	IfcReal
AppliancePercentLoadToRadiant	IfcPositiveRatioMeasure
LightingLoadIntensity	IfcReal
LightingPercentLoadToReturnAir	IfcPositiveRatioMeasure

Table 64 — IfcSite Property Sets for Objects

Quantity Sets

The Quantity Sets concept applies to this entity as shown in Table 65.

Name
Qto_SiteBaseQuantities

Table 65 — IfcSite Quantity Sets

Product Local Placement

The Product Local Placement concept applies to this entity.

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.

FootPrint GeomSet Geometry

The FootPrint GeomSet Geometry concept applies to this entity as shown in Table 66.

Identifier	Type	Items	Description
FootPrint	GeometricCurveSet	IfcGeometricCurveSet	Set of curves (outer and inner) representing the floor projection,

Table 66 — IfcSite FootPrint GeomSet 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).

Survey Points Geometry

The Survey Points Geometry concept applies to this entity as shown in Table 67.

Identifier	Type	Items

Table 67 — IfcSite Survey Points Geometry

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:

IfcShapeRepresentation.RepresentationIdentifier = 'SurveyPoints'
IfcShapeRepresentation.RepresentationType = 'GeometricCurveSet'

Figure 171 shows a set of survey points, given as 3D Cartesian points within the object coordinate system of the site. Figure 172 shows the result after facetation.

The set of IfcCartesianPoint is included in the set of IfcGeometricCurveSet.Elements.


Figure 171 — Site survey points	Figure 172 — Site survey points facetation

Figure 173 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 174 shows the result after facetation.

The set of IfcCartesianPoint and the set of IfcPolyline are included in the set of IfcGeometricCurveSet.Elements.


Figure 173 — Site breaklines	Figure 174 — 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 Geometry

The Body Geometry concept applies to this entity as shown in Table 68.

Identifier	Type

Table 68 — IfcSite Body Geometry

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:

IfcShapeRepresentation.RepresentationIdentifier = 'Body'
IfcShapeRepresentation.RepresentationType = 'Brep', or 'SurfaceModel'

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Common Use Definitions
	Revision Control	Common Use Definitions
IfcObject
	Object Occurrence Predefined Type	Common Use Definitions
IfcSpatialElement
IfcSpatialStructureElement
IfcSite
	Spatial Composition	Common Use Definitions
	Spatial Decomposition	Common Use Definitions
	Spatial Container	Common Use Definitions
	Property Sets for Objects	Common Use Definitions
	Quantity Sets	Common Use Definitions
	Product Local Placement	Common Use Definitions
	FootPrint GeomSet Geometry	Common Use Definitions
	Survey Points Geometry	Common Use Definitions
	Body Geometry	Common Use Definitions

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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