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

[Paul Ramsey]

> 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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