Hello Joe
Le 16/10/13 11:42, Joe White a écrit :
You're correct about the different approach that was taken with Proj4. One of
my greatest issues with it is that the datum transformation feels like it was
more tacked on than designed as a part of a complete system.
This is also my understanding. EPSG has a discussion about what they
call "early binding" and "late binding" implementations
(http://www.ogp.org.uk/pubs/430-1.pdf section 3.4).
* In the "early binding" approach, the datum shift information are
specified at CRS construction time. This is the "TOWGS84" element in
a WKT string, or the "+towgs84" parameter in Proj.4.
* In the "late binding" approach, the datum shift information are
specified at CoordinateOperation construction time, by taking a
second look in the EPSG database after the two CRS (source and
target) are known.
In my understanding, Proj.4 is an "early binding" implementation while
Apache SIS would be a "late binding" implementation. The "late binding"
approach has a stronger needs for a complete EPSG database.
After reading the alternatives, I agree that #3 is the best option. It seems to
flow better, as well as providing less burden on users by reducing the number
of imports to use it.
Thanks for the feedbacks. I will go with #3 then.
Martin
