Hi,
in our existing code base there is a number of places where envelopes
are being reprojected using the method:
CRS.transform(mathTransform, envelope)
This method is fine for a class of transformations, such as affine
transforms
(extensively used to apply grid to world transforms in rasters) and
flattening
transforms (going from a 3d to a 2d envelpe), but it's really bad for
coordinate system transfromations, as it does not know, unlike
CRS.transform(envelope, targetCRS) what the source and target CRS are
This information, the nature of source and target CRS, is important to take
into account singularities such as the poles or the dateline during
transformation:
if we don't take those into account we may get incomplete results.
Point in case, think of an envelope in polar stereographics that contains
the south
pole, we just transform the points at the border (with densification, or
not) and
we'll think that all that was requested was a thin rectangle rather distant
from the pole, because the points at the border of the envelope are there.
Instead, the right result has to expand down to the pole, and span all the
longitudes.
This pull request involved tracking down each and every place where a CRS
transform was made with the "wrong" method, and made it use the "right" one
instead
(the densification during reprojection was alredy implemented when I added
support
for the polar stereographic singularities in CRS.transform(envelope,
targetCRS), previous
this week):
https://github.com/geotools/geotools/pull/457
I've also made a similar set of changes in GeoServer:
https://github.com/geoserver/geoserver/pull/586
If you are maintaining code that does envelope reprojections, I'd suggest
you have
a look too.
Anyways... comments welcomed!
Cheers
Andrea
--
==
Meet us at GEO Business 2014! in London! Visit http://goo.gl/fES3aK
for more information.
==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 1660272
mob: +39 339 8844549
http://www.geo-solutions.it
http://twitter.com/geosolutions_it
-------------------------------------------------------
------------------------------------------------------------------------------
"Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE
Instantly run your Selenium tests across 300+ browser/OS combos.
Get unparalleled scalability from the best Selenium testing platform available
Simple to use. Nothing to install. Get started now for free."
http://p.sf.net/sfu/SauceLabs
_______________________________________________
GeoTools-Devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/geotools-devel
