IfcSite
Definition form IAI: 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 Longitude, Latitude and Elevation) for the project. This definition is given for informational purposes only; it is not intended to provide an absolute placement in relation to the real world.
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.
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 quantities relating to the site are defined by the IfcElementQuantity and attached by the IfcRelAssignsProperties. The following quantities are foreseen, but will be subjected to the local standard of measurement:
Name  Description  Value Type 
SitePerimeter  Perimeter of the Site boundary  length measure 
SiteArea  Gross area for this site (horizontal projections)  area measure 
HISTORY New entity in IFC Release 1.0
ISSUE See issue an change log for changes made in IFC Release 1.5 and in IFC Release 2x.
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.
Standard Geometric Representation
The standard geometric 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 type of the standard geometric representation of IfcSite is:
A set of survey points, given as 3D Cartesian points within the object coordinate system of the site. The set of IfcCartesianPoint is included in the set of IfcGeometricSet.Elements. 

result after facetation  
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. The set of IfcCartesianPoint and the set of IfcPolyline are included in the set of IfcGeometricSet.Elements. 

result after facetation taking the breaklines into account. 
Advanced Geometric Representation
The advanced geometric representation of IfcSite is defined using a surface model, based on the IfcFaceBasedSurfaceModel or on the IfcShellBasedSurfaceModel. Normally the surface model is the result after triangulation of the site survey points.
The representation type of the advanced geometric representation of IfcSite is:
Note: The geometric representation of the site has been based on the ARM level description of the site_shape_representation given within the ISO 10303225 "Building Elements using explicit shape representation".
EXPRESS specification:

RefLatitude  :  World Latitude at Reference point (most likely defined in legal description). Defined as Real values
for Degrees, minutes, seconds. 
RefLongitude  :  World Longitude at Reference point (most likely defined in legal description). Defined as Real values
for Degrees, minutes, seconds. 
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. 
Name  Type  Referred through  ExpressG 
IfcSpatialStructureElement  Entity 

Diagram 1 
