[Proj] datum matters

Frank Warmerdam warmerdam at pobox.com
Sun Mar 29 16:21:19 EST 2009

Paul Kelly wrote:
> I think the sentiment to "do it right" is the key point of contention 
> here. As I see it, it has been the consensus on this list for several 
> years that the way the existing PROJ.4 does this "conflation" is not the 
> best. Indeed PROJ.4 maintainer Frank W has stated several times that it is 
> his long-term intention to refactor the library into a separate 
> "mathematically pure" core (my words not his), probably based on Gerald's 
> libproj4, with a separate level of abstraction on top of that supporting 
> the "less exact" science of co-ordinate system and datum conversions. I 
> don't think anybody has ever seriously disagreed that that was not the 
> best way forward, hence why any suggestion that the current slightly messy 
> way (again my opinion) that projections and co-ordinate systems are mixed 
> in the pj_transform() API is a great idea and the way we should all be 
> doing things is bound to cause a bit of contention ;)


I am less enthusiastic about the refactoring of PROJ.4 into a low level
libproj4 + high level datum/coordinatesystems/etc library now.  My interest
in this was primarily intended to break things into parts where Gerald would
maintain one, and I could maintain the other.  Personally I would have been
happy enough to have the two components conflated for similar reasons to those
mentioned by Richard.

I *feel* that Gerald's recent exit is a sign that he and I are unlikely to
be able to work together effectively on such a two part project and so I am
now inclined to not make any substantive changes in the architecture of
PROJ.4.  In any event the refactoring was predicated on my having a
substantial amount of time to invest which has not materialized over the
last several years.

Frankly, PROJ.4 does what I need now, and I am inclined to continue the
current approach with minimal changes.  If there are other folks who would
like to be contributors in an effort to refactor things, and if they
can convince me they are reasonably sensitive to the impact of changes on
existing users, I would be willing to consider a refactoring effort.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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