In addition to this, I have now been working with IFC geolocation with Cesium, Aerometrex, @john.mitchell and now @lee.gregory - and so I believe to ensure correct implementation it would be useful to supply some test files.
OSArch now provides the IFC2X3 geolocation conventions as a property set template definition which you can download: https://wiki.osarch.org/index.php?title=IFC_geolocation (by the way, the BlenderBIM Add-on can be used to author property set template definitions, should buildingSMART find it useful as a tool)
This should allow for unambiguous implementation of it. This also addresses an omission (I believe) in the buildingSMART user guide where
MapUnit is not discussed. In particular, property sets do not allow an
IfcNamedUnit, and therefore I have reverted it to
You can now find two test files… for IFC2X3: https://github.com/Moult/ifc-test-files/blob/master/src/ifc-spf/geolocation-ifc2x3.ifc … and for IFC4: https://github.com/Moult/ifc-test-files/blob/master/src/ifc-spf/geolocation-ifc4.ifc
For these two files, you should expect to see the following result (I have provided WGS84 for convenience) - a quick sanity check should find the model in the Sydney Opera House
EPSG:4326, or WGS84
EPSG:7856, or GDA2020/MGA56.
EPSG:5111, or AHD.
Scale factor is 1.
The building itself is arrow shaped (how convenient!) with the center of the arrow around the project origin, pointing project north (Y axis - in green):
If properly geolocated, and true north is up the page, you should find the arrow pointing north east by 30 degrees:
Please let me know if you spot any errors, and it would be good to see some other vendors also produce files so we can ensure that we can consume and round-trip them properly.