[gdal-dev] Intersection of two Layers

[Kai Muehlbauer]

Am 22.01.2016 um 10:52 schrieb Ari Jolma:
> 22.01.2016, 10:06, Kai Muehlbauer kirjoitti:
>>
>>
>> To quickly check if there is an improvement I used the python shapely
>> package. Converting the outer loop geometry to an shapely prepared
>> geometry and calling 'contains()' with the inner loop geometries to
>> find those fully contained geometries I get an improvement of nearly
>> 40% to the former ogr only code.
>>
>> As Even pointed out, there is only OGRPreparedGeometryIntersects()
>> (GEOSPreparedIntersects) exposed within ogrgeometry.cpp. In my use
>> case I would need GEOSPreparedContains to mimic the shapely behaviour.
>
> I made a small test with the attached diff, which prepares the
> geometries of the input layer.
>
> The input layer had two polygons (boundaries of two Finnish
> municipalities) and the method layer had 3091 points, all in either one
> of the polygons.
>
> The improvement is ~15%.
>
> I think the prepared geometries could be used by default easily.
> Prepared contains test would need addition of the respective GEOS method.

Thanks Ari, I very much appreciate your efforts in testing layer 
intersection. If the prepared contains test could be done within the 
layer intersection then those features can "just be copied" without the 
need of costly intersection calculation. This would give a real speedup.

So, it would need the addition of the OGRPreparedGeometryContains method 
(GEOSPreparedContains) and then enhancing your patch.
Would it work the way as in the attached diff? Or did I miss something?

What are the next steps to get this feature fully implemented?

Cheers,
Kai


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