IFC for GIS
IFC for GIS
The IFC for GIS project (also known as IFG) was initiated by the Norwegian Strate Planning Authority Statens Bygningstekniske Etat. The aim of the project was to be able to provide geographic information created using GIS systems within the framework of the Industry Foundation Classes (IFC) schema. The reason for this was to support a growing set of business requirements that included:
- Consistent storage of both geographic and building information within a consistent data structure (enabled by a facility for communication between GIS and AEC/FM systems and vice versa)
- Support for the development of planning and building code compliance checking systems (using a similar approach to that applied in the Singapore ePlanchecking project)
IFC for GIS development focussed on support for making the zoning plan and building plan submission process more efficient. Key to this was the integration of GIS information in a central building and property registry with AEC/FM information about the individual buildings that are registered. For a building that is to be dsesigned and constructed, information is taken from the registry to provide location map data including property data, utility services, zoning and more.
The aim of the IFC for GIS project was to use the Industry Foundation Classes (IFC) model as the specification for the exchange of limited but meaningful information between GIS and AEC/FM systems and vice versa. The intent was to use entities that are already established within the Coordination and Code Checking views of the IFC schema so as to be able to reuse as far as possible the tools, techniques and capabilities already developed by vendors at the AEC/FM side of the exchange
The IFG project set out to define a bridge between AEC/FM systems and GIS systems. It did not seek to create a complete geographical information inside IFC. Instead, it recognized the existence of other competent models for this purpose, notably the model underlying the Geographic Markup Language (GML) produced by the Open GIS Consortium (OGC).
The approach to creating the bridge has been to create an ‘overlap’ between such models through the provision of entities whose occurrence and location in coordinate space can be recognized in both the AEC/FM and GIS world. Practically, this means understanding AEC/FM location information in the context of a map projection at a reasonable accuracy. Broadly, the area of overlap is seen as a one kilometre square centred upon a particular building of interest. Within this range, the maximum error at the limits of the square due to the projection of the curvature of the ellipsoid onto a Cartesian plane is estimated at four millimetres.
Having establish a comparative basis for information with the AEC/FM domain and the GIS domain, the IFG project then defined a mapping specification between IFC and GML (and vice versa).
The IFG project also created comparative reports on geometry usage within the IFC and GML specifications and on approaches used for property set definition in IFC and feature specification in GML.