[gdal-dev] Accuracy of OGRLayer:SetSpatialFilter() API

[Frank Warmerdam]

On Tue, Jun 12, 2012 at 10:44 AM, kedardeshpande87
<kedardeshpande87 at gmail.com> wrote:
> I checked the envelope the OGRPoint geometry I have created. This envelope
> is also a single point (minX, maxX are same and minY, maxY are same). So,
> how is it possible that multiple features overlap on the same point ?

Kedard,

Because the *envelope of the polygons* all overlap the point. The envelopes
(ie. bounding rectangles) of the zip code features will overlap substantially so
clearly there will be points which will intersect the envelopes of multiple
polygons.

> For the same shapefile, I checked results by using some other libraries as
> well. Those libraries return a single zipcode. So I am guessing the
> shapefile which I am using does not have overlapping data.

That guess would seem to be based on very faulty intuition.

> Could it be that the vector math done while calculating the intersection of
> filter-geometry and features has some limitations?

Yes, I think that has been covered.  Without GEOS it is just
envelope to envelope comparisons.

I think this will be my last response on this topic since we seem
to be repeating ourselves.

Best regards,
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Software Developer