Implement getting and setting true north rotation independent of grid north

src/ifcopenshell-python/ifcopenshell/api/georeference/data.py

@@ -2,12 +2,14 @@ class Data:
     is_loaded = False
     map_conversion = {}
     projected_crs = {}
+    true_north = {}
 
     @classmethod
     def purge(cls):
         cls.is_loaded = False
         cls.map_conversion = {}
         cls.projected_crs = {}
+        cls.true_north = None
 
     @classmethod
     def load(cls, file):
@@ -15,6 +17,7 @@ class Data:
             return
         cls.map_conversion = {}
         cls.projected_crs = {}
+        cls.true_north = {}
         if file.schema == "IFC2X3":
             return
         for context in file.by_type("IfcGeometricRepresentationContext", include_subtypes=False):
@@ -28,4 +31,9 @@ class Data:
             if cls.projected_crs["MapUnit"]:
                 cls.projected_crs["MapUnit"] = map_conversion.TargetCRS.MapUnit.get_info()
             break
+        for context in file.by_type("IfcGeometricRepresentationContext", include_subtypes=False):
+            if not context.TrueNorth:
+                continue
+            cls.true_north = context.TrueNorth.DirectionRatios
+            break
         cls.is_loaded = True