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Mitch3007

QGIS vs ESRI/Mapinfo projection declarations

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Hi all, 

I am trying to understand why the degree unit for MGA 56 (and other Transverse Mercator projections) is different between ESRI/Mapinfo and QGIS. After a bit of digging online I haven't had much luck. 

The below is a copy of the respective prj files. Note the Mapinfo Universal Translator (essentially FME) creates a prj file consistent with ESRI. 

 

ESRI/Mapinfo

PROJCS["GDA_1994_MGA_Zone_56",GEOGCS["GCS_GDA_1994",DATUM["D_GDA_1994",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",10000000.0],PARAMETER["Central_Meridian",153.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]

 

QGIS

PROJCS["GDA94_MGA_zone_56",GEOGCS["GCS_GDA_1994",DATUM["D_GDA_1994",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",153],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",10000000],UNIT["Meter",1]]

I believe all software packages suggest I am using EPSG 28356. I am concerned that the small difference in units can lead to very slight shifts in large datasets and issues with snapping.

If you have experienced these issues or have any thoughts it would be great to hear from you. Kind regards, Mitch.

ESRI_MGA56.prj.txt

QGIS_MGA56.prj.txt

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