The EPSG Contract

[Paul Ramsey]

Daniel,

I think whether Mapserver is broken is a matter of interpretation. In
GML 2.1, when a CRS is referred to using an EPSG number, is the full
EPSG contract implied? If yes, then mapserver is broken: it returns
EPSG:4326 coordinates in easting/northing order. If no, then mapserver
is fine.

As long as mapserver was hermetically sealed from the problem by not
implementing WMS 1.3 things were fine, but if the problem has leaked in
via GML/WFS support, then things need to be opened up again and a
decision made.

A speak-no-evil, hear-no-evil approach will just lead to sorrow and
wailing in the future. What we need from OGC is a pretty public and
solid directive about "what we mean now when we say EPSG:XXXX" and "what
we meant two years ago when we said EPSG:XXXX". Because the two are not
necessarily the same.

The fact that mapserver is already out of the gates with an
"easting/northing EPSG" implementation of GML/WFS support just puts more
pressure on the issue for resolution.

Paul

PS - I just read through the GML 2 specification and there is no
discussion of axis order issues with respect to EPSG references. Things
are blithely assumed to be "X" and "Y".

Daniel Morissette wrote:

> Paul Ramsey wrote:
>
>>
>> And if we want to follow the direction of the standards bodies (ISO,
>> OGC) then we should do the work ASAP, because the longer implementations
>> with broken contracts are out there, the more bifurcated and
>> non-interoperable the whole "geoweb" is going to get.
>>
>> Thoughts, concerns, etc?
>>
>
> I agree that this EPSG vs WMS 1.3 issue is a big mess, it has generated
> lots of very passionate reactions and discussions... please don't get me
> going on it.  :)
>
> Just to be clear, are you suggesting that MapServer broken in any way at
> the moment with its WMS 1.1.x and WFS 1.0.0 implementeations? I am one
> of those who had a "we're not going there (WMS 1.3)" reaction... not
> going there until we really have to anyway, and since WMS 1.3 brings
> nothing new that WMS 1.1.1 didn't have, I see no need to go there. As
> you replied to me on related topic before: what would that investment
> give me that I don't have already?  ;)
>
> Anyway, if something is plain broken according to the OGC specs then
> we'll look at it and fix it. Otherwise, my plan was to procrastinate
> until we are forced to support WMS 1.3, or until the problem goes away
> by itself in a future WMS revision (my secret hope).
>
> Daniel