[udig-devel] intersection/disjunction of layers?

[Vince Darley]

At 16:50 17/12/2007, Jesse Eichar wrote:
>I've been working on something for this sort of issue.  But it is not
>ready in uDig yet.  It will be based on a Geotools construct which
>allows a layer to be constructed from an Arbitrary SQL statement.
>Perhaps you can look into that.  Jody should hopefully know more.

Can anyone point me to more information on this sort of thing?  --- 
constructing layers from other layers through operations (potentially 
in SQL) such as intersection/disjunction/merge/etc.

thanks!

Vince.

>>I have several layers related to a road network.  Each is composed
>>of LineStrings or similar.  These layers are all different views/ 
>>subsets of an underlying postgres table of road segments -- all
>>referenced by a primary "road segment id" key.
>>
>>I'm wondering if uDig (or any community plugins) provide an easy way
>>to see, for any pair of such layers, which road segments are shared
>>by the two layers and which are not shared - i.e. intersection and
>>disjunction of the sets of road segments.
>>
>>Any known capabilities which cover this?
>>
>>regards,
>>
>>Vince.
>>
>>_______________________________________________
>>User-friendly Desktop Internet GIS (uDig)
>>http://udig.refractions.net
>>http://lists.refractions.net/mailman/listinfo/udig-devel
>
>_______________________________________________
>User-friendly Desktop Internet GIS (uDig)
>http://udig.refractions.net
>http://lists.refractions.net/mailman/listinfo/udig-devel
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>
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Vince Darley
CEO, Eurobios UK Ltd
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