[postgis-users] simplify creates geom collection?

[Kevin Neufeld]

Design flaw?  "simplify" does not maintain geometry validity.  
Self-intersections or geometry collapses can occur. The docs state this 
... well, that geometries may no longer be simple anyway.

I suppose we could change this so that a geometry clean-up is performed 
after the simplification ... but we would need to develop a proper 
geometry "rebuilder" function first :)

-------------
Kevin Neufeld
Software Developer
Refractions Research Inc.
300-1207 Douglas St.
Victoria, B.C., V8W 2E7

Phone: (250) 383-3022
Email: kneufeld at refractions.net



Martin Davis wrote:
> I think you'd call this a design flaw.  It sounds like JTS has a 
> similar problem.  Can you post your test cases?
>
> Burgholzer,Robert wrote:
>>
>> I have experienced an instance where using simplify, depending on the 
>> threshold chose, creates a geometry collection, rather than a 
>> multipolygon (which was my source shape type).
>>
>>  
>>
>> I am unsure of exactly what is happening, but I know that with my 
>> particular shapes, a threshold of 0.0025 (dd) caused the problem, but 
>> 0.002 was OK.
>>  
>>
>> Is this a bug, a feature, or operator error?
>>
>>  
>>
>> Robert W. Burgholzer
>>
>> Surface Water Modeler
>>
>> Office of Water Supply and Planning
>>
>> Virginia Department of Environmental Quality
>>
>> rwburgholzer at deq.virginia.gov <mailto:rwburgholzer at deq.virginia.gov>
>>
>> 804-698-4405
>>
>> Open Source Modeling Tools:
>>
>> http://sourceforge.net/projects/npsource/
>>
>> Web-Based Water Supply Planning Demo:
>>
>> http://soulswimmer.dynalias.net/models/wsdemo/demo_hsi.php
>>
>>  
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>   
>