Converting project length units now intelligently preserves map unit and coordinate operation scale.

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

@@ -164,6 +164,7 @@ class BatchReassignClass:
 class Migrator:
     def __init__(self):
         self.migrated_ids = {}
+        self.attribute_overrides = {}
         self.class_4_to_2x3 = json.load(open(os.path.join(cwd, "class_4_to_2x3.json"), "r"))
         self.class_2x3_to_4 = json.load(open(os.path.join(cwd, "class_2x3_to_4.json"), "r"))
 
@@ -224,7 +225,6 @@ class Migrator:
         }
 
     def preprocess(self, old_file: ifcopenshell.file, new_file: ifcopenshell.file):
-        self.attribute_overrides = {}
         to_delete = set()
 
         if old_file.schema == "IFC2X3" and new_file.schema == "IFC4":
@@ -262,7 +262,7 @@ class Migrator:
         except:
             pass
         # print("Migrating", element)
-        schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name(new_file.schema)
+        schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name(new_file.schema_identifier)
         new_element = self.migrate_class(element, new_file)
         # print("Migrated class from {} to {}".format(element, new_element))
         new_element_schema = schema.declaration_by_name(new_element.is_a())

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

@@ -417,16 +417,12 @@ def get_project_unit(ifc_file: ifcopenshell.file, unit_type: str) -> Union[ifcop
     """Get the default project unit of a particular unit type
 
     :param ifc_file: The IFC file.
-    :type ifc_file: ifcopenshell.file
     :param unit_type: The type of unit, taken from the list of IFC unit types,
         such as "LENGTHUNIT".
-    :type unit_type: str
     :return: The IFC unit entity, or nothing if there is no default project
         unit defined.
-    :rtype: Union[ifcopenshell.entity_instance, None]
     """
-    unit_assignment = get_unit_assignment(ifc_file)
+    if unit_assignment := get_unit_assignment(ifc_file):
-    if unit_assignment:
         for unit in unit_assignment.Units or []:
             if getattr(unit, "UnitType", None) == unit_type:
                 return unit
@@ -591,13 +587,9 @@ def convert_unit(value: float, from_unit: ifcopenshell.entity_instance, to_unit:
     """Convert from one unit to another unit
 
     :param value: The numeric value you want to convert
-    :type value: float
     :param from_unit: The IfcNamedUnit to confirm from.
-    :type from_unit: ifcopenshell.entity_instance
     :param to_unit: The IfcNamedUnit to confirm from.
-    :type to_unit: ifcopenshell.entity_instance
     :return: The converted value.
-    :rtype: float
     """
     return convert(
         value, getattr(from_unit, "Prefix", None), from_unit.Name, getattr(to_unit, "Prefix", None), to_unit.Name
@@ -612,17 +604,11 @@ def convert(value: float, from_prefix: Optional[str], from_unit: str, to_prefix:
     already available as IFC entities, consider using convert_unit() instead.
 
     :param value: The numeric value you want to convert
-    :type value: float
     :param from_prefix: A prefix from IfcSIPrefix. Can be None
-    :type from_prefix: str, optional
     :param from_unit: IfcSIUnitName or IfcConversionBasedUnit.Name
-    :type from_unit: str
     :param to_prefix: A prefix from IfcSIPrefix. Can be None
-    :type to_prefix: str, optional
     :param to_unit: IfcSIUnitName or IfcConversionBasedUnit.Name
-    :type to_unit: str
     :return: The converted value.
-    :rtype: float
     """
     if from_unit.lower() in si_conversions:
         value *= si_conversions[from_unit.lower()]
@@ -656,11 +642,8 @@ def calculate_unit_scale(ifc_file: ifcopenshell.file, unit_type: str = "LENGTHUN
         si_meters / unit_scale = ifc_project_length
 
     :param ifc_file: The IFC file.
-    :type ifc_file: ifcopenshell.file
     :param unit_type: The type of SI unit, defaults to "LENGTHUNIT"
-    :type unit_type: str
     :returns: The scale factor
-    :rtype: float
     """
     if not ifc_file.by_type("IfcUnitAssignment"):
         return 1
@@ -690,24 +673,19 @@ def format_length(
 
     :param value: The value in meters if metric, or either decimal feet or
         inches if imperial depending on input_unit.
-    :type value: float
     :param precision: How precise the format should be. I.e. round to nearest.
         For imperial, it is 1/Nth. E.g. 12 means to the nearest 1/12th of an
         inch.
-    :type precision: float
     :param decimal_places: How many decimal places to display. Defaults to 2.
-    :type decimal_places: int
     :param suppress_zero_inches: If imperial, whether or not to supress the
         inches if the inches is zero.
-    :type suppress_zero_inches: bool
     :param unit_system: Choose whether your value is "metric" or "imperial"
-    :type unit_system: str
     :param input_unit: If imperial, specify whether your value is "foot" or
         "inch".
-    :type input_unit: str
     :param output_unit: If imperial, specify whether your value is "foot" to
         format as both feet and inches, or "inch" if only inches should be
         shown.
+    :returns: The formatted string, such as 1' - 5 1/2".
     """
     if unit_system == "imperial":
         if input_unit == "foot":
@@ -747,9 +725,7 @@ def format_length(
 
 
 def is_attr_type(
-    content_type: ifcopenshell_wrapper.parameter_type,
+    content_type: ifcopenshell_wrapper.parameter_type, ifc_unit_type_name: str, include_select_types: bool = True
-    ifc_unit_type_name: str,
-    include_select_types: bool = True
 ) -> Union[ifcopenshell_wrapper.type_declaration, None]:
     cur_decl = content_type
 
@@ -821,15 +797,16 @@ def iter_element_and_attributes_per_type(
 
 def convert_file_length_units(ifc_file: ifcopenshell.file, target_units: str = "METER") -> ifcopenshell.file:
     """Converts all units in an IFC file to the specified target units. Returns a new file."""
+    import ifcopenshell.util.element
+    import ifcopenshell.util.geolocation
+
     prefix = get_prefix(target_units)
     si_unit = get_unit_name(target_units)
 
     # Copy all elements from the original file to the patched file
     file_patched = ifcopenshell.file.from_string(ifc_file.wrapped_data.to_string())
 
-    unit_assignment = get_unit_assignment(file_patched)
+    old_length = get_project_unit(file_patched, "LENGTHUNIT")
-
-    old_length = next(u for u in unit_assignment.Units if getattr(u, "UnitType", None) == "LENGTHUNIT")
     if si_unit:
         new_length = ifcopenshell.api.unit.add_si_unit(file_patched, unit_type="LENGTHUNIT", prefix=prefix)
     else:
@@ -856,7 +833,28 @@ def convert_file_length_units(ifc_file: ifcopenshell.file, target_units: str = "
             new_value = convert_value(val)
             setattr(element, attr.name(), new_value)
 
+    has_map_unit = False
+    if (
+        ifc_file.schema == "IFC2X3"
+        and (crs := ifcopenshell.util.element.get_pset(ifc_file.by_type("IfcProject")[0], name="ePSet_ProjectedCRS"))
+        and crs.get("MapUnit")
+    ) or (ifc_file.schema != "IFC2X3" and (crs := ifc_file.by_type("IfcProjectedCRS")) and crs[0].MapUnit):
+        has_map_unit = True
+
+    if has_map_unit:
+        parameters = ifcopenshell.util.geolocation.get_helmert_transformation_parameters(ifc_file)
+        ifcopenshell.api.georeference.edit_georeferencing(
+            file_patched,
+            coordinate_operation={
+                "Eastings": parameters.e,
+                "Northings": parameters.n,
+                "OrthogonalHeight": parameters.h,
+                "Scale": parameters.scale / convert_value(1),
+            },
+        )
+
     file_patched.remove(old_length)
+    unit_assignment = get_unit_assignment(file_patched)
     unit_assignment.Units = tuple([new_length, *unit_assignment.Units])
 
     return file_patched

src/ifcopenshell-python/test/util/test_unit.py

@@ -19,6 +19,8 @@
 import test.bootstrap
 import ifcopenshell.api.unit
 import ifcopenshell.api.root
+import ifcopenshell.api.georeference
+import ifcopenshell.util.geolocation
 import ifcopenshell.util.unit as subject
 from math import pi
 
@@ -92,3 +94,73 @@ class TestIsAttrType(test.bootstrap.IFC4):
         assert subject.is_attr_type(nominal_value, "IfcValue")
         assert subject.is_attr_type(nominal_value, "IfcLengthMeasure")
         assert not subject.is_attr_type(nominal_value, "IfcLengthMeasure", include_select_types=False)
+
+
+class TestConvertFileLengthUnits(test.bootstrap.IFC4):
+    def test_run(self):
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        unit = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT", prefix="MILLI")
+        ifcopenshell.api.unit.assign_unit(self.file, units=[unit])
+        output = subject.convert_file_length_units(self.file, target_units="METER")
+        assert subject.get_full_unit_name(subject.get_project_unit(output, "LENGTHUNIT")) == "METRE"
+
+    def test_converting_map_conversion_if_there_is_no_map_unit(self):
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        unit = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT", prefix="MILLI")
+        ifcopenshell.api.context.add_context(self.file, "Model")
+        ifcopenshell.api.georeference.add_georeferencing(self.file)
+        ifcopenshell.api.georeference.edit_georeferencing(self.file, coordinate_operation={"Eastings": 10000})
+        ifcopenshell.api.unit.assign_unit(self.file, units=[unit])
+        output = subject.convert_file_length_units(self.file, target_units="METER")
+        assert subject.get_full_unit_name(subject.get_project_unit(output, "LENGTHUNIT")) == "METRE"
+        assert output.by_type("IfcMapConversion")[0].Eastings == 10
+
+    def test_preserving_enh_if_there_is_a_map_unit(self):
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        unit = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT", prefix="MILLI")
+        meter = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT")
+        ifcopenshell.api.context.add_context(self.file, "Model")
+        ifcopenshell.api.georeference.add_georeferencing(self.file)
+        ifcopenshell.api.georeference.edit_georeferencing(
+            self.file, projected_crs={"MapUnit": meter}, coordinate_operation={"Eastings": 10, "Scale": 0.001}
+        )
+        ifcopenshell.api.unit.assign_unit(self.file, units=[unit])
+        output = subject.convert_file_length_units(self.file, target_units="METER")
+        assert subject.get_full_unit_name(subject.get_project_unit(output, "LENGTHUNIT")) == "METRE"
+        assert output.by_type("IfcMapConversion")[0].Eastings == 10
+        assert output.by_type("IfcMapConversion")[0].Northings == 0
+        assert output.by_type("IfcMapConversion")[0].Scale == 1
+        assert subject.get_full_unit_name(output.by_type("IfcProjectedCRS")[0].MapUnit) == "METRE"
+
+
+class TestConvertFileLengthUnitsIFC2X3(test.bootstrap.IFC2X3):
+    def test_converting_map_conversion_if_there_is_no_map_unit(self):
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        unit = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT", prefix="MILLI")
+        ifcopenshell.api.context.add_context(self.file, "Model")
+        ifcopenshell.api.georeference.add_georeferencing(self.file)
+        ifcopenshell.api.georeference.edit_georeferencing(self.file, coordinate_operation={"Eastings": 10000})
+        ifcopenshell.api.unit.assign_unit(self.file, units=[unit])
+        output = subject.convert_file_length_units(self.file, target_units="METER")
+        assert subject.get_full_unit_name(subject.get_project_unit(output, "LENGTHUNIT")) == "METRE"
+        parameters = ifcopenshell.util.geolocation.get_helmert_transformation_parameters(output)
+        assert parameters.e == 10
+
+    def test_preserving_enh_if_there_is_a_map_unit(self):
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        unit = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT", prefix="MILLI")
+        meter = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="LENGTHUNIT")
+        ifcopenshell.api.context.add_context(self.file, "Model")
+        ifcopenshell.api.georeference.add_georeferencing(self.file)
+        ifcopenshell.api.georeference.edit_georeferencing(
+            self.file, projected_crs={"MapUnit": subject.get_full_unit_name(meter)}, coordinate_operation={"Eastings": 10, "Scale": 0.001}
+        )
+        ifcopenshell.api.unit.assign_unit(self.file, units=[unit])
+        output = subject.convert_file_length_units(self.file, target_units="METER")
+        assert subject.get_full_unit_name(subject.get_project_unit(output, "LENGTHUNIT")) == "METRE"
+        parameters = ifcopenshell.util.geolocation.get_helmert_transformation_parameters(output)
+        assert parameters.e == 10
+        assert parameters.n == 0
+        assert parameters.scale == 1
+        crs = ifcopenshell.util.element.get_pset(output.by_type("IfcProject")[0], name="ePSet_ProjectedCRS")
+        assert crs["MapUnit"] == "METRE"