[Geowanking] Re: [OSGeo-Discuss] Input regarding Axis Order Confusion

[Arnulf Christl]

On Sat, December 16, 2006 05:41, Raj Singh wrote:
> Let me try to clarify. There's a clear path forward in OGC to specify
> WGS84 decimal degrees in X,Y order. It's to use this CRS:
> urn:x-ogc:def:crs:OGC:1.3:CRS84
>
> So there's no need for another organization to define one.

If you say so. But I only believe when I see. I do not see anything yet
anywhere in this respect:
http://www.opengeospatial.org/search/node/urn%3Ax-ogc%3Adef%3Acrs%3AOGC%3A1.3%3ACRS84
http://www.opengeospatial.org/search/node/CRS84
let alone Google, it finds:
http://www.imatchup.com/man_seeking_woman/NC-meet-crs84.html

My job is being a pain in the axis, sorry about that but now that we have
so much attention we might as well get over with it.

Wankers, most of this sounds a lot like "internal OGC" business but I
think that "internal" is the problem here not "OGC". Shoo me off the list
if you think that I only choke it with annoying or boring stuff.

Other organizations have btw. done a better job of addressing the issue,
especially implementors like GeoTools or OSGeo itself:
http://www.google.com/search?q=axis+order&start=0&ie=utf-8&oe=utf-8&client=firefox-a&rls=org.mozilla:en-US:official

> Now, the only problem is that so many people have grown accustomed to
> thinking

Well, I wouldn't say that it is a problem when people get accustomed to
thinking. It is more of a problem when people only think in accustomed
ways. :-)

> EPSG:4326 means X,Y order that we worry about people having
> to get used to a different name. I know "urn:x-ogc:def:crs:OGC:
> 1.3:CRS84" is very long, but that's what happens when people try to
> be extremely precise about their meaning. If you just read the above

...and search for more information to understand what it is supposed to
mean you draw a blank. urn:nothing in WMS 1.3 docs. We need examples and a
concise explanation that is intelligible to the standard geek who manages
to put together a Google-Messup. :-) Maybe address this in WG Mass Market,
now that it is on the OGC Agenda...

> and starting screaming about the length of the string, a community

There is no need to start screaming about anything yet as (at least I)
cannot see the full implications. But for humane interfaces we need to
hide this string behind something more intelligible anyway. Is that the
job of "a community" as you suggest here, or should this rather happen
inside out the OGC? I'd vote for the latter but it'd better happen soon.

And I wonder what happens to all the other CRS that are lurking out there?

Just another fine example: The Federal State of Brandenburg (the one
around Berlin) carries a leading digit in their x-axis value to denote the
origin meridian. Unfortunately EPSG does not do this resulting  in an
offset of several thousand km rendering Brandenburg near Moscow. Mind me
this is officially publicly available data!

> could adopt a convention to use "OGC1.3CRS84" to mean the same thing
> without losing any precision.
> ---
> Raj

Thanks again for jumping in everybody and bear in mind that we are just
scraping the surface of a depper rooted problem. We need to do a lot more
education.

Who will update CRS in the OGC's glossary:
http://www.opengeospatial.org/resource/glossary/c

Oh, now that I read this, it is confusing again:

coordinate system
    Composed of a set of coordinate axes with a known metric. The concept
'metric of a coordinate space' consists of the set of mathematical
rules that defines the relationships between the coordinate values and
the invariant spatial quantities between points; for example, the
mathematical rules (formulae) required for calculating angles and
distances between points from coordinate values and vice versa.

So it is "mathematical rules" that apply in coordinate systems? They are
(x,y). So much work to do...

Regards,

> On Dec 15, 2006, at 2:23 PM, Arnulf Christl wrote:
>
>>> So nobody present at the OGC meeting saw the issue? It's not about
>>> deciding which one is "correct" between x,y, or y,x, or lon,lat, or
>>> lat,lon ... I could not care less as long as pick one and only one
>>> and
>>> go with it. Variable axis order based on SRS code like what has been
>>> introduced in WMS 1.3 is the worst possible situation for
>>> interoperability IMNSHO.
>>
>> I am missing out on a practical alternative. If I get this right "we"
>> would need to create a repository with coordinate reference systems
>> that
>> go for x,y(,z) and go "our" own way. This will be a stony way so I
>> propose
>> in my stylish humble way to stick with 1.1.1 as long as we can and
>> undercover try to find that new database.
>
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-- 
Arnulf Christl
http://www.ccgis.de