ArcGIS Desktop, shapefile and EPSG code

Question

Why does a shapefile with CRS WGS_1984_UTM_Zone_22N in ArcGIS have a different prj file than the EPSG:32622:WGS 84 / UTM zone 22N WKT ?

Can I replace the ArcGIS .prj file with EPSG:32622 WKT?

GS_1984_UTM_Zone_22N prj file

PROJCS["WGS_1984_UTM_Zone_22N",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-51.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]

WGS 84 / UTM zone 22N WKT

PROJCS["WGS 84 / UTM zone 22N",GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-51],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],AUTHORITY["EPSG","32622"],AXIS["Easting",EAST],AXIS["Northing",NORTH]]

Answer 1

If you're not using 10.1, you could create a .prj file with the EPSG-style WKT version (EPSG Geodetic Parameter Dataset has no official WKT format) and place it in the Coordinate Systems, Projected Coordinate Systems folder. Because ArcGIS includes name comparisons when it checks for equality, the WGS 84 definition will not be recognized as equivalent to the GCS_WGS_1984 definition used in the predefined geographic/datum transformations, so you would have to create custom transformation if any are needed.

In 10.1, you can still create a .prj file, but the Coordinate System folder has been removed. Store the file somewhere and use the Import option on the various coordinate system tab or tools to browse and select the file.

Finally, functionally (mathematically), the two definitions are equivalent.

Disclaimer, I guess: I work at Esri and I'm on the subcommittee that maintains the EPSG dataset.