[geos-devel] Union problem

[mchapman at texelinc.com]

Martin,

Thank you for confirming that.  I will look at my code and validate that I am not screwing up the points after the geos operation. If not, I will try my best to debug through the geos source and look for the problem.

By chance do you have a recommendation on where I should start looking in the union operation source code for this issue? Could I put a linearRing.isClosed() method call somewhere in the union code to trap the violating ring? 

Thanks again for all your help!

Best regards,
Martin.  





.
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-----Original Message-----
From: Martin Davis <mbdavis at refractions.net>

Date: Fri, 04 Apr 2008 12:17:41 
To:GEOS Development List <geos-devel at lists.osgeo.org>
Subject: Re: [geos-devel] Union problem


This works fine in JTS.

Unfortunately I don't have GEOS running, so can't test it there.  
Possibly we could look into that during some future work.

It is a bit suspicious that it looks like the offending point is the 
terminating point of the last ring in the US MultiPolygon.

M



Martin Chapman wrote:
> Martin,
>
> Here you go.  It occurs when you union the US and Mexico. Thanks for your
> help!
>
> Best regards,
> Martin
>
>
> -----Original Message-----
> From: geos-devel-bounces at lists.osgeo.org
> [mailto:geos-devel-bounces at lists.osgeo.org] On Behalf Of Martin Davis
> Sent: Thursday, April 03, 2008 12:32 PM
> To: GEOS Development List
> Subject: Re: [geos-devel] Union problem
>
> Send me the shapefile and I'll try it out in JTS.
>
> M
>
> Martin Chapman wrote:
>   
>> Unfortunately, I do not have JTS but I will try to step through the code
>>     
> and
>   
>> see if I can learn more about the problem.  Perhaps a careful inspection
>>     
> of
>   
>> the input and output point sets will yield some clues because the problem
>>     
> is
>   
>> predictable.
>>
>> Best regards,
>> Martin
>>
>> -----Original Message-----
>> From: geos-devel-bounces at lists.osgeo.org
>> [mailto:geos-devel-bounces at lists.osgeo.org] On Behalf Of Paul Ramsey
>> Sent: Thursday, April 03, 2008 11:50 AM
>> To: GEOS Development List
>> Subject: Re: [geos-devel] Union problem
>>
>> Most probably a bug... any chance you could run this same test case
>> under JTS so we can confirm if it's a problem at the algorithm level
>> or the port level?
>>
>> Thanks,
>>
>> P
>>
>> On Thu, Apr 3, 2008 at 10:47 AM, Martin Chapman <mchapman at texelinc.com>
>> wrote:
>>
>>   
>>     
>>> All,
>>>
>>> When I union the two features USA and Mexico I end up with a geometry
>>>       
> that
>   
>>> has one point where the y or lat value for one point is zero.  See the
>>> attachment for what I mean.  Does anyone think this is a bug in GEOS or
>>>       
> am
>   
>>>     
>>>       
>> I
>>   
>>     
>>> not doing something correctly?  Most other geometric unions create good
>>> geometries.  If you want I can send the original shape file.
>>>
>>>
>>>
>>> Thanks for any help.
>>>
>>>
>>>
>>> Best regards,
>>>
>>> Martin
>>>
>>>
>>> _______________________________________________
>>>  geos-devel mailing list
>>>  geos-devel at lists.osgeo.org
>>>  http://lists.osgeo.org/mailman/listinfo/geos-devel
>>>
>>>     
>>>       
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>>   
>>     
>
>   
> ------------------------------------------------------------------------
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022

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