[geos-devel] Aggregate on attribute

Paul Meems bontepaarden at gmail.com
Mon Mar 3 03:08:13 PST 2014

Thanks Sandro for the quick reply.

I understand how to solve this using a database.

For now we're going to look closer to our own function and fix the issues
were facing.



 *Paul Meems *
Release manager, configuration manager
and forum moderator of MapWindow GIS.

Owner of MapWindow.nl - Support for
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*Join us at the MapWindow GIS Conference 2014
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2014-03-03 11:31 GMT+01:00 Sandro Santilli <strk at keybit.net>:

> On Mon, Mar 03, 2014 at 11:15:52AM +0100, Paul Meems wrote:
> > Hi List,
> >
> > We use with MapWinGIS (C++ ActiveX control) GDAL with GEOS.
> >
> > We currently have a custom AggregateShapefile method which is not using
> > GEOS.
> > In this method we aggregate (union) all shapes based on an attribute.
> This
> > method is not working 100% and I'm wondering if GEOS has something
> similar.
> GEOS has no support for "attributes".
> It'll need to be built outside.
> > For example I have the counties shapefile of the USA. I want to aggregate
> > all counties that are in the same state.
> > I know of the Union method in GEOS, but that doesn't takes into account
> the
> > attribute and in this example will result in a shapefile with 1 shape
> > instead of a shape for each state.
> >
> > Any advice will be much appreciated.
> PostGIS would sound like an appropriate tool for what you're trying to do.
> --strk;
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