fix logic and text of the reported outcome for correct interpretation of Scale attribute

Author: civilx64

features/rules/GRF/GRF005_CRS-unit-type-differences.feature

@@ -1,15 +1,14 @@
 @industry-practice
 @GRF
-@version1
-@E00100
+@version2
 Feature: GRF005 - CRS unit type differences
 The rule verifies that the Scale attribute of IfcMapConversion is used when the units of the CRS are not identical to the units of the engineering coordinate system.
 If omitted, the value of 1.0 is assumed.
 If the units of the referenced source location engineering coordinate system are different from the units of the referenced target coordinate system,
-then this attribute must be included and must have the value of the scale from the source to the target units
+then this attribute must be included and must have the value of the scale from the project units to the target of the map coordinate units.
 
 
-  Scenario: In cases where the length unit of the local CRS differs from the length unit of the external CRS, the map conversion scale must reflect the factor between the two units.
+  Scenario: IfcMapConversion Scale attribute
 
     Given A model with Schema 'IFC4' or 'IFC4.3'
     Given An .IfcMapConversion.

features/steps/steps/crs.py

@@ -53,7 +53,7 @@ def get_horizontal_unit_factors(crs: CRS) -> set[float]:
 @gherkin_ifc.step("The map conversion scale must be the quotient of the project length units and the target CRS length units")
 def step_impl(context, inst):
     error_found = False
-    proj_unit_factor = unit.calculate_unit_scale(context.model, unit_type='LENGTHUNIT')
+    project_unit_factor = unit.calculate_unit_scale(context.model, unit_type='LENGTHUNIT')
     map_conversion_scale = getattr(inst, 'Scale', 1.)
     map_conversion_scale_factor = 1.0 if not map_conversion_scale else map_conversion_scale
 
@@ -75,19 +75,19 @@ def step_impl(context, inst):
                 # Relative tolerance of 1E-9 corresponds to 1 part per billion.
                 # This is appropriate for imperial projects using Northing and Easting coordinates
                 # that are often in the range 1E6 or even 1E7.
-                if not isclose(crs_unit_factor, proj_unit_factor, abs_tol=0., rel_tol=1E-9):
+                if not isclose(crs_unit_factor, project_unit_factor, abs_tol=0., rel_tol=1E-9):
                     error_found = True
                     yield ValidationOutcome(inst=inst,
-                                        observed=f"map conversion scale {map_conversion_scale} does not reflect mismatch of target CRS unit conversion factor {crs_unit_factor} and project length unit scale {proj_unit_factor}",
+                                        observed=f"map conversion scale {map_conversion_scale} does not reflect mismatch of target CRS unit conversion factor {crs_unit_factor} and project length unit scale {project_unit_factor}",
                                         severity=OutcomeSeverity.ERROR)
             else:
                 # Scale factor provided for IfcMapConversion.
                 # Confirm that it matches the expected value.
-                quotient = crs_unit_factor / proj_unit_factor
+                quotient = project_unit_factor / crs_unit_factor
 
                 if not isclose(quotient, map_conversion_scale_factor, abs_tol=0., rel_tol=1E-9):
                     error_found = True
-                    yield ValidationOutcome(inst=inst, observed=f"map conversion scale {map_conversion_scale} does not reflect the quotient of the target CRS unit conversion factor {crs_unit_factor} divided by the project length unit scale {proj_unit_factor}", severity=OutcomeSeverity.ERROR)
+                    yield ValidationOutcome(inst=inst, observed=f"map conversion scale {map_conversion_scale} does not reflect the value of the project length unit factor of the project unit factor {project_unit_factor} divided by the target CRS unit factor {crs_unit_factor}", severity=OutcomeSeverity.ERROR)
 
     if not error_found:
         yield ValidationOutcome(inst=inst, severity=OutcomeSeverity.PASSED)

…005/pass-grf005-scaled_foot_to_metre.ifc …rf005-scaled_metre_to_US_survey_foot.ifctest/files/GRF/grf005/pass-grf005-scaled_foot_to_metre.ifc renamed to test/files/GRF/grf005/pass-grf005-scaled_metre_to_US_survey_foot.ifc test/files/GRF/grf005/pass-grf005-scaled_foot_to_metre.ifc renamed to test/files/GRF/grf005/pass-grf005-scaled_metre_to_US_survey_foot.ifc

@@ -2,7 +2,7 @@ ISO-10303-21;
 /* IFC units are in metres, ESPG:2277 uses survey foot and the map conversion reflects this */
 HEADER;
 FILE_DESCRIPTION(('ViewDefinition [ReferenceView]'),'2;1');
-FILE_NAME('pass-grf005-scaled_foot_to_metre.ifc','2023-01-25T18:40:40',(''),(''),'','IfcOpenShell contributors - IfcOpenShell - v0.7.0+6180d73f','');
+FILE_NAME('pass-grf005-scaled_metre_to_US_survey_foot.ifc','2023-01-25T18:40:40',(''),(''),'','IfcOpenShell contributors - IfcOpenShell - v0.7.0+6180d73f','');
 FILE_SCHEMA(('IFC4X3_ADD2'));
 ENDSEC;
 DATA;
@@ -27,6 +27,6 @@ DATA;
 #19=IFCUNITASSIGNMENT((#13,#14,#15,#18));
 #20=IFCPROJECT('2X9wjf5oPB4PQjenCYrhHZ',#5,'',$,$,$,$,(#11),#19);
 #21=IFCPROJECTEDCRS('EPSG:2277',$,'NAD83',$,'','3',$);
-#22=IFCMAPCONVERSION(#11,#21,316131.64,5690966.11,1.,1.,0.,0.30480060960121924);
+#22=IFCMAPCONVERSION(#11,#21,316131.64,5690966.11,1.,1.,0.,3.2808333333333);
 ENDSEC;
 END-ISO-10303-21;