18.01.2016, 11:56, Kai Muehlbauer kirjoitti:
Hi,
at the moment I calculate the intersection of two OGR Layers (A, B) by
iterating over features/geometries (GA) of layer A and then calling
GA.Intersection(GB) for every Feature/Geometry (GB) of B. I set a
spatial filter for layer B with every GA. The intersections
features/geometries are written to a result layer (C).
In my use case the features/geometries of layer B are much smaller
than the features of layer A. Means that quite a big number of B's
geometries are fully contained in A's geometries.
To speed things up, I check for containment GA.contains(GB). If GB is
contained in GA, I just copy GB to C, otherwise I calculate
GA.Intersection(GB) and write this to C.
I found that I also could use the layer intersection function
(OGRLayer::Intersection). Unfortunately the intersection is calculated
for every feature/geometry.
Would it be possible to extend the layer intersection function to
allow for containment check (eg. as an option) and just copy the
contained geometries without calculation of expensive intersection?
Suggestions, opinions?
There's the Options argument, which could be used. Something like
"PRETEST=CONTAINMENT" could indicate a wish to test containment before
intersection.
A test dataset and a patch would be useful.
Ari
In my use case I get improvements of around 20% of processing time.
Cheers,
Kai
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