On Sat, Oct 27, 2012 at 11:42 PM, Tom Kunicki <[email protected]> wrote:
>
> Hello,
>
> We've found a regression between GeoTools 2.6.3 as compared with 2.7.5 and
> 8.2 with regard to datum equality.
>
> In GeoTools 2.6.3 (the version used for prj2epsg.org) we can successfully
> resolve the following WKT provided with an ESRI sourced shapefile as
> EPSG:3071:
>
> PROJCS["NAD_1983_HARN_Transverse_Mercator",
>     GEOGCS["GCS_North_American_1983_HARN",
>         DATUM["D_North_American_1983_HARN",
>             SPHEROID["GRS_1980",6378137.0,298.257222101]],
>             PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
>     PROJECTION["Transverse_Mercator"],
>     PARAMETER["False_Easting",520000.0],
>     PARAMETER["False_Northing",-4480000.0],
>     PARAMETER["Central_Meridian",-90.0],
>     PARAMETER["Scale_Factor",0.9996],
>     PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]
>
> In GeoTools 2.7.5 and 8.2 the conversion of the above WKT to and EPSG code
> fails and I've isolated this the the fact the datum name doesn't match the
> expected EPSG datum name of "NAD83 (High Accuracy Regional Network)".  The
> WKT below with the datum name replaced does resolve to EPSG:3071 in GeoTools
> 2.75 and 8.2
>
> PROJCS["NAD_1983_HARN_Transverse_Mercator",
>     GEOGCS["GCS_North_American_1983_HARN",
>         DATUM["NAD83 (High Accuracy Regional Network)",
>             SPHEROID["GRS_1980",6378137.0,298.257222101]],
>             PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
>     PROJECTION["Transverse_Mercator"],
>     PARAMETER["False_Easting",520000.0],
>     PARAMETER["False_Northing",-4480000.0],
>     PARAMETER["Central_Meridian",-90.0],
>     PARAMETER["Scale_Factor",0.9996],
>     PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]
>
> From my investigation, it appears that datum name is important in
> comparisons and I came across the GeoTools DatumAlias factory and the
> associated DatumAliasesTable.txt.  This factory does have an entry mapping
> the EPSG datum name to the ESRI datum name, and the aliases are added to the
> Datum instance but this relationship doesn't appear to be used when doing
> datum comparisons.   I would think that if a datum name doesn't match the
> datum aliases should then be consulted. Is this current behavior intended or
> a regression?

It indeed looks like a regression. Patches welcomed :-)

Cheers
Andrea


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