OptionalDescriptionOptionalDirectionOptionalGlobalExplicit GlobalId (22-char IFC GUID); generated when omitted.
OptionalNameOptionalObjectOptionalPositionGrid origin, storey-local (metres). Default [0, 0, 0].
OptionalPredefinedIfcGrid PredefinedType (IFC4+; dropped on IFC2X3).
At least one axis.
At least one axis.
OptionalWOptional third family (triangular grids).
Rotation of the grid about Z, radians (0 = grid X along storey X). Default 0.