[geos-devel] GEOS NG Regression Review (GDAL feedback)

[Paul Ramsey]

Problem found and fixed, thanks Even!

https://github.com/libgeos/geos/commit/49ac5aa4

P

> On Sep 17, 2020, at 9:02 AM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> 
> 
> 
>> On Sep 17, 2020, at 8:50 AM, Martin Davis <mtnclimb at gmail.com> wrote:
>> 
>> Thanks for testing, Even.
>> 
>> Interestingly, in JTS the test case you give below for OverlayNG.intersection actually returns the same result as the old code:
>> 
>> MULTILINESTRING ((833978.557030887 0, 835092.849076364 0), (832864.275023695 0, 833978.556808034 0))
>> 
>> So this is something to look into on the GEOS side.
> 
> I have confirmed this happens in GEOS, with a little unit test, so it's nothing to do with GDAL. Looks like a morning in the debugger awaits.
> 
> P
> 
> 
>> 
>> On Thu, Sep 17, 2020 at 4:39 AM Even Rouault <even.rouault at spatialys.com> wrote:
>> 
>> 
>> The intersection of the input geometry with this multipolygon of 2 parts can be shown with:
>> 
>> from osgeo import ogr
>> 
>> # input geometry crossing the antimeridian (UTM 60N)
>> geom = ogr.CreateGeometryFromWkt('LINESTRING(832864.275023695 0,835092.849076364 0)')
>> 
>> # multipolygon with one part left to the antimeridian, one part right
>> geom2 = ogr.CreateGeometryFromWkt('MULTIPOLYGON (((832864.275023695 0.0,833978.556808034 -0.000110682755987,833978.556808034 0.0,833978.556808034 0.000110682755987,832864.275023695 0.0,832864.275023695 0.0)),((835092.849076364 0.0,833978.557030887 -0.000110682755987,833978.557030887 0.0,833978.557030887 0.000110682755987,835092.849076364 0.0,835092.849076364 0.0)))')
>> 
>> # intersection
>> print(geom.Intersection(geom2))
>> 
>> With OverlayNG, the following leads to a LINESTRING EMPTY, whereas with GEOS 3.8something, it leads to the expected result of
>> MULTILINESTRING ((832864.275023695 0.0,833978.556808034 0.0),(833978.557030887 0.0,835092.849076364 0.0))
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>