Wednesday, 4 November 2015

The correct setup of your CAD model for export to IFC

I am exploring today, the correct geospatial set up of a CAD model, so that it may be exported correctly to IFC. You may wonder why, well its simple really, to accurately describe the position of any material, located within a component, in any element, in a 3D model we need to use the X,Y,Z coordinates.

In the past, we have relied heavily on the use of a simple grid to locate column positions, and to describe the position of say a door in a 2D model, and to some extent this will still work in a 3D model, but to accurately describing the failure point within a cavity wall to a computer program, needs a spacial grid, that is linked to the real world. Enter the use of a global position system,

In the UK we use the National Grid Ordnance Survey Geographic Cartesian coordinates system, or Eastings and Northings, its position can be linked to almost any other grid method from the various Lat Long methods, to the variety of country grids operating about the globe, almost always we buy maps as a digital file, which when imported into almost all CAD programs, auto sets the OS grid correctly.

The process as described in the IFC Building Smart support group paper, which the conclusion so well describes the need :

"The conceptual model is used to conceptualize the data structure to capture the required information for all exchange purposes and level of definition. The purpose of the conceptual model is:  Being a means to communicate with the expert panel on the correct data schema definitions;  Being a means to correlate the buildingSMART P6 work with OGC to achieve a common conceptual schema for both, the future GML extensions developed by OGC and the IFC extensions developed by buildingSMART;  Being the starting point to then incorporate the additional data schema requirements into the IFC EXPRESS and IFC XSD schema".

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