[wms-dev] Re: [mapserver-users] Projection EPSG code for LCC in mapserv 3.5

[Martin Daly]

My understanding was that using "EPSG:xxxx" was a pragmatic solution to a
complex problem.  GML 3.0 will have XML encoding of co-ordinate reference
systems (much more powerful than existing WKT), and support for CRS
dictionaries, e.g. for on-line repositories containng CRS definitions that
can be referenced with a URI.

This will remove the dependence on EPSG, and the problem of using CRS-s that
do not have an EPSG code will disappear in an instant ... or at least the
problem will be changed and moved somewhere else.

Regards,
Martin Daly,
Technical Director,
Cadcorp Ltd
e: martin at cadcorpdev.co.uk
w: www.cadcorp.com
t: +44 (0) 20 7383 0014
f: +44 (0) 20 7388 6313

----- Original Message -----
From: "Rob Atkinson" <rob at socialchange.net.au>
To: "Paul Ramsey" <pramsey at refractions.net>
Cc: "Daniel Morissette" <morissette at dmsolutions.ca>; "Trem Stamp"
<trem at socialchange.net.au>; "Mapserv Users List"
<mapserver-users at lists.gis.umn.edu>; <wms-dev at intl-interfaces.net>
Sent: Thursday, November 22, 2001 5:58 AM
Subject: [wms-dev] Re: [mapserver-users] Projection EPSG code for LCC in
mapserv 3.5


>
> Interesting discussion this.
>
> IMHO - and I've been involved with both mapserver and WMS since inception,
the
> use of codes allows a greater degree of discovery through service
registries,
> and ability of client to discover how to negotiate a binding with the
service.
> WMS is all about interoperability after all. The lack of a better taxonomy
is
> a broader issue - the solution would be to have an active engagement with
an
> ISO process so that each country has a simple means to register its WKT
> (actually the model for the projection) and get a code assigned as
required.
>
> RA
>
> Paul Ramsey wrote:
>
> > This dependence on the EPSG authority has got to be the worst aspect of
> > the WMS spec. There are scads of useful (and widely used!) projections
> > which EPSG does not have codes for. So now people are just randomly
> > adding codes willy nilly. ESRI has already done so, in their
> > "predefined" projections provided with ArcGIS8. They took the EPSG list,
> > dropped a few projections, and then added a bunch of new ones of their
> > own. I can send a proj4-style epsg file with the ESRI-added codes to
> > anyone who needs it.
> >
> > What I do not understand is why the WMS spec does not support WKT as a
> > means of defining projection information in the first place. Ironically,
> > ArcIMS *does* support WKT for defining projection information.
> >
> > Daniel Morissette wrote:
> > >
> > > > Trem Stamp wrote:
> > > >
> > > > Does anyone know if there is an EPSG code for LCC projection
> > > > information?  I seem to remember looking last time and couldn't fine
> > > > one so had to use the following type of syntax:
> > > >
> > > >   PROJECTION
> > > >   "proj=lcc"
> > > >   "ellps=aust_SA"
> > > >   "lat_0=-32.5"
> > > >   "lon_0=147.0"
> > > >   "lat_1=-29.5"
> > > >   "lat_2=-36.5"
> > > >   END
> > > >
> > > > If there is no EPSG code for this currently, does anyone know if
there
> > > > is likely to be in the near future?
> > > >
> > >
> > > Trem,
> > >
> > > We ran into the same issue for Canadian LCC projections... there
wasn't
> > > any in the official list of EPSG codes.  But you can edit the
> > > /usr/local/share/proj/epsg file to add your own codes... that's what
we
> > > ended up doing... read on...
> > >
> > > Cubewerx which is actively involved in all that WMS stuff had also run
> > > into this issue and resolved it by defining its own extension to the
> > > EPSG list for LCC and other projections useful to canadians.  They
used
> > > custom EPSG codes in the range 42100-42399.  We adopted the same codes
> > > for our own WMS implementations and added (some of) them to our local
> > > "epsg" file, so our clients and servers can exchange LCC projection
with
> > > other servers that also adopted Cubewerx's EPSG extension.
> > >
> > > Question to Frank W: Do you think the 42100-42399 custom EPSG codes
> > > could be added to the official "epsg" file distributed with PROJ4?
> > >
> > > Now, I realize that this doesn't resolve your problem with Australian
> > > projections not having an EPSG code... I think you should raise this
> > > issue on the WMS-Dev list and see if a better solution to this problem
> > > has been adopted.
> > > (See http://www.intl-interfaces.net/mailman/listinfo/wms-dev)
> > >
> > > --
> > > ------------------------------------------------------------
> > >  Daniel Morissette               morissette at dmsolutions.ca
> > >  DM Solutions Group              http://www.dmsolutions.ca/
> > > ------------------------------------------------------------
> > >   Don't put for tomorrow what you can do today, because if
> > >       you enjoy it today you can do it again tomorrow.
>