Thanks for the clear explanations Andrea,
now I got the points and have everything I need to move this all to the
udig list.
Geotools has everything defined, so I think what's left out is a part of
the behavioural part in Udig.
I'll wait for the UDig list to react to this.

Ciao
Andrea




Andrea Aime probaly wrote:
> Andrea Antonello ha scritto:
>> Andrea Aime probaly wrote:
>> I don't understand you exactly. When you use reprojection for calculus
>> and not just for visualization, things can get bad if the system does
>> what it wants without asking. So when I create a map from a shapefile,
>> why shouldn't the system ask for the proper values, if there is
>> ambiguity? If the user doesn't know, it can get back to a lenient
>> tranform.
> 
> Then you have to setup a new CRS object from scratch, and believe me it
> may be quite painful if you do that code wise
> (there was a tutorial once on how to build a CRS from its basic
> elements, where did it end up?).
> Once build a CRS object is immutable, so you cannot just take the 3003
> version you got form the EPSG database and alter it.
> 
> Since you're using uDig 1.0.1 you can also locate the epsg.properties
> file and add your custom projections, with custom codes
> and custom wkt, something like (taking the pensinsular params):
> 
> 10003003=PROJCS["Monte Mario / Italy zone 1 / Pensinsular optimized",
>    GEOGCS["Monte Mario",
>      DATUM["Monte Mario",
>        SPHEROID["International 1924", 6378388.0, 297.0,
>  AUTHORITY["EPSG","7022"]],
>       TOWGS84[104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68]
>        AUTHORITY["EPSG","6265"]],
>      PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
>      UNIT["degree", 0.017453292519943295],
>      AXIS["Geodetic longitude", EAST],
>      AXIS["Geodetic latitude", NORTH],
>      AUTHORITY["EPSG","4265"]],
>    PROJECTION["Transverse Mercator", AUTHORITY["EPSG","9807"]],
>    PARAMETER["central_meridian", 9.0],
>    PARAMETER["latitude_of_origin", 0.0],
>    PARAMETER["scale_factor", 0.9996],
>    PARAMETER["false_easting", 1500000.0],
>    PARAMETER["false_northing", 0.0],
>    UNIT["m", 1.0],
>    AXIS["Easting", EAST],
>    AXIS["Northing", NORTH],
>    AUTHORITY["EPSG","3003"]]
> 
> (but you'll have to write the wkt in a single line).
> 
> The epsg.properties file is located inside the epsg-wkt jar. Not sure
> the uDig guys setup anything for user customization, that is something
> only them can answer.
> 
> Cheers
> Andrea
> 

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