Geolocation utilities now support converting either X axis or Y axis to an angle

src/blenderbim/blenderbim/bim/module/georeference/operator.py

@@ -145,7 +145,7 @@ class SetNorthOffset(bpy.types.Operator):
 
     def execute(self, context):
         context.scene.sun_pos_properties.north_offset = -radians(
-            ifcopenshell.util.geolocation.xy2angle(
+            ifcopenshell.util.geolocation.xaxis2angle(
                 context.scene.BIMGeoreferenceProperties.map_conversion.get("XAxisAbscissa").float_value,
                 context.scene.BIMGeoreferenceProperties.map_conversion.get("XAxisOrdinate").float_value,
             )

src/ifcopenshell-python/ifcopenshell/util/geolocation.py

@@ -94,6 +94,16 @@ def global2local(matrix, eastings, northings, orthogonal_height, x_axis_abscissa
     )
 
 
-# Used for converting the X and Y vectors of the X Axis in IFC geolocation
-def xy2angle(x, y):
+# Used for converting the X and Y vectors of the X Axis in IFC grid north geolocation
+def xaxis2angle(x, y):
     return math.degrees(math.atan2(y, x))
+
+
+# Used for converting the X and Y vectors of the Y Axis in IFC true north geolocation
+def yaxis2angle(x, y):
+    angle = math.degrees(math.atan2(y, x)) - 90
+    if angle < -180:
+        angle += 360
+    elif angle > 180:
+        angle -= 360
+    return angle