[postgis-users] Problem with slow GeomUnion (geom, geom)

[Håvard Tveite]

This is probably a map overlay, and not a traditional spatial join.
See:

<URL: http://en.wikipedia.org/wiki/Geographic_information_system#Map_overlay >

The PostGIS Intersection(geometry,geometry) is a relevant
operation.

Håvard

Mark Cave-Ayland wrote:
> On Fri, 2007-06-01 at 12:00 +0200, Matt Doughty wrote:
>> Hi Mark,
>>
>> I'm trying to do a geometric union (I'm more used to doing these things
>> in ArcGIS where it'd be a union: A topological overlay of two or more
>> polygon spatial datasets that preserves the features that fall within
>> the spatial extent of either input dataset; that is, all features from
>> both datasets are retained and extracted into a new polygon dataset
>> (ESRI website))
>>
>> In this case I'm not bothered about what happens to attributes, it's the
>> polygons that I want.
>>
>> The input tables are as follows:
>>
>>       1. Table1
>>               name character varying(70),
>>               the_geom geometry
>>       2. Table 2
>>               name character varying(70),
>>               the_geom geometry
>> Cheers,
>>
>> Matt
> 
> Okay, this is getting a little out of my comfort zone so someone else
> may need to help out here - is basically what you want to return all the
> polygons that overlap each other from your two tables?
> 
> 
> Kind regards,
> 
> Mark.
> 
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> ILande - Open Source Consultancy
> http://www.ilande.co.uk
> 
> 
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-- 
Håvard Tveite
Department of Mathematical Sciences and Technology, UMB
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