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List:       postgis-users
Subject:    Re: [postgis-users] Strange intersection behavior
From:       Andreas Albarello <andreas.albarello () territoriumonline ! com>
Date:       2008-12-29 22:52:20
Message-ID: C4D41494-FEF6-4095-82BD-59BD4D1B37F1 () territoriumonline ! com
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On 29 Dec 2008, at 19:19, Obe, Regina wrote:

> Andreas,
>
> I think you have unearthed one of the cruel lessons of floating  
> point math.
>
> Best described in Isaac Kunen's blog.
>
> http://blogs.msdn.com/isaac/archive/2008/08/07/the-imprecise-nature-of-geometry.aspx
>

Thanks a lot, Regina. I feared something like that might be the cause  
of all this, but it's certainly reassuring to know that workarounds  
using ST_Distance and ST_DWithin with some epsilon value instead of  
ST_Intersects are common practice in these cases.

Best regards,
--
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Andreas Albarello
Analysis & SW Development

Territorium Online srl/GmbH
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email: andreas.albarello@territoriumonline.com
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