[josm-dev] New projection required for a new plugin

[Pieren]

Dear all,

I'm currently developing a JOSM plugin to access a french WMS which will be
a very useful source of data for OSM (it's the french land register called
'cadastre').
I'll not talk about the legal aspects here (ref.[1]) but the license clearly
allows the derived works for free like we will do with JOSM (using the
images as a back layer).
My idea is to create a plugin which will extend the existing WMSplugin
because we need to start the session in a special way and the wms delivers
only one commune (town/city/village) images per request (city code embedded
in url).

My current problem is more technical and concern the projection : the WMS
returns images projected with the french Lambert zone system (ref.[2]) only.
This is the traditional projection system used here in France. It's called
"Zone" because the country is divided in 3 zones plus one for Corsica.

Now, I would like to know your opinion about the best way to proceed:
- either keep the current available projections, retrieve the images and
re-project them under the current existing projection. But I have the
feeling that it is not so easy to do (not only stretching the lines). But I
saw a proof-on-concept example on your ML archives (ref.[3]).
- the other possibility is to implement the Lambert zone projection, which
is something I've already successfully tried. But I was not able to do it
without changing the josm class Projection which contains the
allProjections() method.

Do you have any plan in the future to make extra projections possible from
plugins without changing the josm core files ?
Or shall I implement the Lambert zone project in the standard available
projections of JOSM (but that could raise more questions/problems from the
users and the list is potentially increasing a lot) ?

Thanks for your help.
Pieren

[1] License of cadastre (
http://www.cadastre.gouv.fr/scpc/html/CU_01_ConditionsGenerales_fr.html) (in
french)
[2] Lambert conformal conic projection (
http://en.wikipedia.org/wiki/Lambert_conformal_conic_projection)
[3] 2007-Novemeber : Change JOSM default projection from EPSG:4326 to
Mercartor? (
http://lists.openstreetmap.org/pipermail/josm-dev/2007-November/000428.html)