The version of the IFC standard that extends the data model to infrastructure: roads, rail, ports and waterways. Its central contribution is the alignment (IfcAlignment), which describes the horizontal and vertical layout and lets elements be referenced to it.

How is it different from IFC4?

IFC4 targets buildings. IFC4x3 adds the entities of linear works — alignments, roads, rail, earthworks — and tightens georeferencing, which is essential in infrastructure because projects span kilometres.

Can I open an IFC4x3 without paid software?

Yes. Geoma opens IFC2x3, IFC4 and IFC4x3 in the browser, with nothing installed and without uploading the file.

Why do many viewers open an IFC4x3 empty?

Because their geometry engine only covers the building schema. If the viewer does not recognise the infrastructure entities, it shows the model incomplete or blank.

IFC4x3 for infrastructure: what changes and how to open it

IFC4x3 is the version of the standard that finally covers infrastructure: roads, rail, ports and waterways. If you work in linear works, it is the schema your models will arrive in — and the one many viewers still fail to open properly.

Open an IFC4x3 — free See the viewer

What it adds over IFC4 and IFC2x3

	IFC2x3	IFC4	IFC4x3
Focus	Buildings	Buildings	Buildings + infrastructure
Alignment	No	No	Yes (IfcAlignment: horizontal, vertical and cant)
Linear works elements	Generic	Generic	Road, rail, earthworks, signage…
Georeferencing	Via IfcSite placement	IfcMapConversion	IfcMapConversion, essential here
Typical use	Legacy exchange	Buildings	Roads, rail, drainage, linear structures

The key piece: the alignment

In a building, the reference is the floor plan. In linear works, it is the alignment. IFC4x3 introduces IfcAlignment, describing the horizontal layout (straights, curves, transition spirals), the vertical profile and the cant, and letting each element be referenced to a chainage instead of a loose coordinate. That is what makes a 12 km model manageable: you navigate by chainage, not by coordinates.

Why some viewers open it empty

Because their geometry engine only understands the building schema: if it does not recognise the infrastructure entities, it shows the model incomplete or nothing at all. Before writing a file off as broken, open it in something that declares IFC4x3 support — Geoma does — and check whether the problem was the model or the viewer.

The other usual cause of "nothing shows up" is not the schema but the georeference: the model is fine, just loaded 400 km from where you are looking.

Working with an IFC4x3 in practice

Filter by chainage. Narrow to the stretch you care about and apply changes only there, instead of across 12 km.
Federate by discipline. Alignment, structures, drainage and services arrive as separate files: federate them by real coordinates and they fit without touching them.
Check the georeference file by file before coordinating anything. In linear works an origin error is invisible until you have already measured wrong.
Complete the control data — phase, contract, asset code — with batch editing, which is how these models are handed to the client.

Frequently asked questions

What is IFC4x3?: The version of the IFC standard extending the data model to infrastructure, with the alignment as its central contribution.
Can I open it without paid software?: Yes: it opens in the browser alongside IFC2x3 and IFC4, with nothing installed and no upload.
Can I edit an IFC4x3?: Yes — properties, elements, position and georeference. What you cannot edit is the geometry itself; that belongs in the authoring tool. See the editor.
What if my client still asks for IFC2x3?: Still the norm in buildings. You can work with both, and when merging files of different schemas you are warned and offered a conversion.

Open my linear works model UTM coordinates in an IFC