compare spatial references

Question

In order to compare the spatial reference of my map and this of my database I use the following code: var mapSR = myMap.ActiveView.SpatialReference; var gdbSR = ((IGeoDataset)myFeatureClass).SpatialReference; bool areSame = ((IClone)mapSR).IsEqual((IClone)gdbSR); if(areSame) // also compare map-resolution as suggested here: https://desktop.arcgis.com/en/arcobjects/latest/net/webframe.htm#ISpatialReference_IsPrecisionEqual.htm mapSR.IsPrecisionEqual(gdbSR, out areSame);‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ After calling IsPrecisionEqual areSame will be false (I ensured the method was called by setting a breakpoint), which I don´t understand. When I dive into the spatial references, e.g. using a watch, I can´t see any (meaningful) differences: (ISpatialReferenceResolution)mapSR COM Object [System.__ComObject]: COM Object Abbreviation: "" Alias: "" FactoryCode: 0 MResolution: 0.0001 MResolution: 0.0001 MTolerance: 0.001 MToleranceValid: esriSRToleranceOK Name: "ETRS89_UTM32" PrecisionExImpl: 1529763776 PrecisionImpl: 1533456216 Remarks: "" SpatialReferenceImpl: 689094056 VerticalCoordinateSystem: null XYTolerance: 0.0001 XYToleranceValid: esriSRToleranceOK ZCoordinateUnit: null ZTolerance: 0.001 ZToleranceValid: esriSRToleranceOK (ISpatialReferenceResolution)gdbSR COM Object [System.__ComObject]: COM Object Abbreviation: null Alias: null FactoryCode: 0 MResolution: 0.0001 MResolution: 0.0001 MTolerance: 0.001 MToleranceValid: esriSRToleranceOK Name: "ETRS89_UTM32" PrecisionExImpl: 1103993808 PrecisionImpl: 1100159248 Remarks: null SpatialReferenceImpl: 689094056 VerticalCoordinateSystem: null XYTolerance: 0.0001 XYToleranceValid: esriSRToleranceOK ZCoordinateUnit: null ZTolerance: 0.001 ZToleranceValid: esriSRToleranceOK ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ Also get_XYResolution(false) returns 0.00001 (which is 10times the XYTolerance, as seen above) for both the maps and the databases spatial reference. I also tried to use ISpatialReference3.IsXYResolutionEqual, because I´m only interested in plane resolution and tolerance. However this also returns false when comparing the two spatial references. So what do IsXYResolutionEqual and IsResolutionEqual compare asside from the above properties? Are those Impl- and ExImp-properties considered as well (which is not documented)?

CarstenSchumann · Answer

As you see in my code I already use IClone.IsEqual. However as of the docs this does not consider any information about precision and tolerance, which is why I use IsPrecisionEqual.

GKmieliauskas · Answer

Hi Carsten,

Do you need to check are spatial references are exactly the same? If yes, you could use IClone method IsEqual. I also tried to use IsXYPrecisionEqual, but without success.