[MetaCRS] Introduction]

[Landon Blake]

Martin,

I may not have been very clear on this point. You are correct when you state the definitions wouldn't be changed, but that new ones would be added. The same problem would exist: Each source of CRS definitions or transformation algorithms could be in a different state of "currentness" or "correctness". If I happen to be using a library that can't tap into one of these sources that is updated first, I am at a disadvantage. 

Having a single source eliminates this problem. It allows us to focus efforts on maintenance of CRS definitions and/or transformation algorithms in a single place.

It's all about consolidation...

Landon

-----Original Message-----
From: Martin Desruisseaux [mailto:martin.desruisseaux at geomatys.fr] 
Sent: Thursday, May 15, 2008 7:43 AM
To: Landon Blake
Cc: Rutger Bezema; metacrs at lists.osgeo.org
Subject: Re:[MetaCRS] Introduction]

Landon Blake a écrit :
> Our buddy Frank is on the ball. He was able to get some funding, and has
> updated all of the proj4 configuration files to reflect the changes. But
> the boys at the EPSG are behind the 8 ball. They haven't made the
> changes. Neither has the deegree project, most of their customers are in
> Europe, and they aren't terribly excited about paying for updates to CRS
> definitions used exclusively in North America.
> 
> Now we've got a real chocolate mess.
> 
> But, if we had a single "super CRS" library", Frank, the programmers
> from the deegree Project, and the programmers from OpenJUMP (especially
> those in North America) could coordinate a single update of one source
> of CRS definitions. That means one update,  one download, on source for
> the latest and greatest CRS information. It means that we aren't
> repeating the same update work across four (4) or (5) CRS definition
> libraries.


I'm not sure to understand the issue... If North America come with a new datum, 
EPSG will not update the existing CRS for the new datum. Instead, they will 
create new codes for new CRS using the new datum. The old CRS will be left 
unchanged or, at most, deprecated. EPSG would also probably provide information 
about how to transform from the old CRS to the new CRS.

We really don't want existing CRS definition to be changed for the new datum, 
because we must known that legacy data are using the old CRS. If european don't 
download the updated EPSG database, they will not have the codes for the newly 
added CRS, but the existing one would stay identical so they would be basically 
unaffected.

Or did I missed something?

	Martin



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