Thanks for the summary Andrea; I suspect your could define both "EPSG:0" and
CRS:1" as backed on to the same class. We do allow coordinate reference
systems to list multiple identifiers so this would not be out of place.
You may also wish to steal some of the documentation from CRS:1 in
describing this beast.
With respect to the concept, I think it is a clear idea, and will be
well received.
Jody
On Thu, Apr 28, 2011 at 7:37 PM, Andrea Aime
<[email protected]>wrote:
> Hi,
> some months ago I started a discussion on GeoServer devel about
> adding support for a new EPSG code, EPSG:0.
> (if you want to review that discussion see here:
>
> http://osgeo-org.1803224.n2.nabble.com/Generic-cartesian-CRS-code-zero-td6136122.html
> )
>
> ESPG:0 would represent pure cartesian data, lack of any referencing, and
> would
> thus be associated to DefaultEngineeringCRS.GENERIC_2D, which is designed
> to be
> a lenient wildcard CRS, from the javadoc:
>
> ----------------
>
> A two-dimensional wildcard coordinate system with x, y axis in metres.
> At the difference of CARTESIAN_2D, this coordinate system is treated
> specially by the
> default coordinate operation factory with loose transformation rules:
> if no transformation
> path were found (for example through a derived CRS), then the
> transformation from this
> CRS to any CRS with a compatible number of dimensions is assumed to be the
> identity transform. This CRS is usefull as a kind of wildcard when no
> CRS were explicitly specified.
>
> ---------------
>
> The only different would be that this one would be constructed so that it
> reports being EPSG:0 as being its "name".
>
> The idea behind EPSG:0 is to be able to handle non georeferenced data,
> or data that is expressed in some unkonwn coordinate system.
> This would allow to natively handle CAD data in vector land and plain
> images in raster land still using our GeoTools Feature/Coverage concepts,
> and avoid users to try and force EPSG:4326 in it instead (because it's
> often
> the only code they remember).
>
> As far as I can see this fits well with our existing code base, that
> already
> uses in some places DefaultEngineeringCRS.GENERIC_2D when no
> native CRS could be found, this work would just give it a name.
>
> Gabriel on the old thread raised a good point that the WMS 1.3 spec also
> has
> CRS:1 as the identifier to be used for the same purpose.
> I'm not going to go down that road because this would require making a
> large
> amount of changes to many bits of existing code assuming the authority
> is always going to be ESPG, both in GeoTools and GeoServer.
> The day we go there and allow the library to function properly without
> those
> assumption its going to be easy to add a further alias to that CRS
> and have it respond as CRS:1 as well.
>
> To wrap up, I'd like to add a new authority factory in referencing that
> adds support for that code and then check that base stores and coverage
> readers are working properly with it.
> Since this is an addition it's not going to break code not using it,
> thus I propose to commit the changes on both trunk and 2.7.x
>
> Opinions?
>
> Cheers
> Andrea
>
> --
> -------------------------------------------------------
> Ing. Andrea Aime
> GeoSolutions S.A.S.
> Tech lead
>
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
>
> phone: +39 0584 962313
> fax: +39 0584 962313
>
> http://www.geo-solutions.it
> http://geo-solutions.blogspot.com/
> http://www.youtube.com/user/GeoSolutionsIT
> http://www.linkedin.com/in/andreaaime
> http://twitter.com/geowolf
>
> -------------------------------------------------------
>
>
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