[Shapelib] Identify polygon by XY coordinate?

[shapelib-admin at lists.maptools.org]

shapelib-admin at lists.maptools.org wrote:
> List,
>     I need a function that uses (X,Y) coordinates to identify the 
> surrounding polygon in a shapefile, and then retrieve the associated 
> attribute information for that polygon.
>     Does anyone have a function like that?

Bob,

The ogrinfo utility will approximately do this; however, it doesn't do
real point-in-polygon tests, it just verifies that the bounding box of
the polygon(s) intersects the target point(or region).  If that is
sufficient then you would use something like:

ogrinfo -ro -spat 481710 4752312 481710 4752312 polygon.shp polygon

   http://ogr.maptools.org

There is a point-in-polygon available in the CVS version of Shapelib if you
would like to construct a program to do this yourself.  I haven't tried the
point in polygon code, but I assume it works ok.  It may require some digging
to figure out how to use it and build an app to do the full operation.

I have attached the readme and code I received for this.  It should work with
a regular release shapelib.

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 Programmer for Rent

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