[Geotiff] [MetaCRS] question on GeoTiff axis order

[johann sorel]

Hello,

I agree that it would be a huge work to fix everything.
Still I am what we could call part of the 'new' generation of GIS 
developers (only 25 years old, doing gis since 4years ago).
I first discover the problem when working on WMS, a big mess without 
axis order which is not clearly define even today with the wms 2 working 
group going on. Before that I was always working using the strict EPSG, 
considering others as anomalies.
I don't know what happened in the past to make things the way they are 
today, from what I understand, the 'change' first occured in proj4 and 
because it's widely used, the 'change' has spread. Something pretty 
similar to the google pseudo mercator, just another anomaly which has 
spread so widely that it can't be fixed anymore.
The way I see things, is that this ambigious case of axis order, the 
futur generations will have it too ... frustrating and for me unacceptable.

At least I see a way to solve the problem concerning GeoTiff, since 
there is nowhere in the tiff metadata tags where 'EPSG' is written, the 
only thing written in the tags is the numeric code. We could declare a 
new authority (which could be named LEPSG for LongitudeFirstEPSG) and 
specify that geotiff relys on this authority. Nothing to change in the 
code, no files to fix and no more ambiguity.
Just saying that geotiff rely on a  EPSG but with longitude first is not 
enought, how do you define which ones are flipped ? at least a rule must 
be given like the one given by frank, but does this rule matches all cases ?

My proposal is a bit naive and doesn't solve the problem for other 
formats, but at least the problem would be stopped in geotiff.

johann sorel







Le 17/12/2010 20:01, Norm Olsen a écrit :
> Hello All . . .
>
> I'm on board with Frank on this one.  We certainly could go and redo all this to be the "correct way"; but at the cost of many man years of effort for virtually no benefit at all.  The end result after experiencing many years of agony and pain would be pretty much what we have now as technology advancement would have to take a big hit to provide the resources to achieve "axis order correctness".
>
> Virtually every GIS/CAD/CAM system expects the first ordinate of a coordinate array to increase to the east, and the second ordinate to increase to the north, and the third ordinate (if present) to increase away from the center of the earth.
>
> While it is nice to be "correct", the price of "correcting" 30 years of software development makes this idea unthinkable.
>
> Norm Olsen
>
>
> -----Original Message-----
> From: metacrs-bounces at lists.osgeo.org [mailto:metacrs-bounces at lists.osgeo.org] On Behalf Of Martin Desruisseaux
> Sent: Friday, December 17, 2010 10:33 AM
> To: metacrs at lists.osgeo.org; geotiff at lists.maptools.org
> Subject: Re: [MetaCRS] question on GeoTiff axis order
>
> Le 17/12/10 18:15, Frank Warmerdam a écrit :
>> My approach is to assume long/lat for geographic coordinate systems, but
>> (in theory at least) to honour EPSG axis order for projected coordinate
>> systems.
> This rule sound a nice compromise to me: unambiguous while simple, and probably
> matching a majority of common practices :). Thanks for the clarification.
>
>
>> I'm cc:ing the geotiff list since that is really where this discussion
>> should be.
> The http://www.remotesensing.org/geotiff/faq.html#Status FAQ entry gave us the
> feeling that the GeoTIFF mailing list was not active anymore, but I think that
> we have misunderstood this FAQ entry.
>
> 	Martin
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