At 11:07 AM 12/22/2008, Frank Warmerdam wrote:
Kevin Webb wrote:
Greetings!
The documentation for the OGRGeometry class mentions the GEOS library in
a few of the
method definitions, but I wonder if there is a "stronger" OGR dependency
on the GEOS
library than the documentation suggests. Perhaps GEOS should be a
required library.
I had done some processing using OGRGeometry::Intersects() without the
GEOS library
installed, I then installed GEOS to run the same tests using
OGRGeometry::Distance().
After installing GEOS, but before running the OGRGeometry::Distance()
tests, I re-ran the
code using OGRGeometry::Intersects() and noticed different intersection
results.
Before-GEOS, the Intersects() method indicated intersection with 2 layer
polygons. After-GEOS,
the Intersects() method indicated intersection with 1 layer polygon.
Note: After-GEOS results
for both Intersects() and Distance() == 0 were the same.
Should the GEOS library be a requirement for deterministic OGR processing?
Kevin,
The Intersects() is bounding box based without GEOS, and based on
actual geometry intersection if it is available. That is presumably
why your results differ.
For a large number of people OGR is just fine without GEOS, so I see
no reason to make it a fixed dependency. It might be prudent to better
document the caveats of operating without it.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
Thank you for your reply Frank.
Giving the documentation a boost should provide some relief.
KFW
-----------------------------------------
Kevin Webb
Programmer/Analyst
Cornell Lab of Ornithology
159 Sapsucker Woods Rd.
Ithaca, NY 14850
Tel: 607.254.2103
Fax: 607.254.2415
k...@cornell.edu
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