Function ifc_angle_to_kml_heading 

pub fn ifc_angle_to_kml_heading(
    x_abscissa: Option<f64>,
    x_ordinate: Option<f64>,
) -> f64

Convert the IFC angle-to-grid-north (counter-clockwise from map east, via the IfcMapConversion X-axis abscissa/ordinate) into a KML <Model><Orientation><heading>, a clockwise rotation of a model whose local X-axis starts pointing east. Returns 0 when either component is absent. KML heading is not a compass bearing: at heading = 0 the X-axis already points east (KML’s baseline), and rotating clockwise by heading moves it to true bearing 90 + heading, so reaching bearing B takes B - 90 (mod 360).