[postgis-users] Spurious Results using ST_Split

[Jeff Adams - NOAA Affiliate]

Thanks for the response Remi-C. Could you please give me a brief overview
of what the workaround would involve? Is this a reported issue?


On Fri, May 23, 2014 at 8:08 AM, Rémi Cura <remi.cura at gmail.com> wrote:

> Hey,
> it looks like a classical precision issue.
> There are some workaround but they are a little bit annoying.
>
> Cheers,
> Rémi-C
>
>
> 2014-05-23 13:46 GMT+02:00 Jeff Adams - NOAA Affiliate <
> jeff.adams at noaa.gov>:
>
>> Greetings,
>>
>> I have been working with the st_split function and have been receiving
>> strange results. Specifically, I have been using a polygon geometry to
>> split a linestring geometry. After the split I have been using st_within to
>> identify which of the resulting split linestring geometries are inside and
>> which are outside. Sometimes the st_within results are as expected, other
>> times, split linestring geometries that are clearly within the polygon
>> feature (they were created using the polygon as the blade) are not
>> identified as so. When checking in ArcGIS, the features that returned false
>> using the st_within function in PostGIS (but by the nature of how they were
>> created should be within the polygon) are being identified by ArcGIS as
>> being within the polygon. Does anybody know why PostGIS' st_within is
>> returning false with these features? Any workarounds? I am performing this
>> analysis on a fairly large dataset.
>>
>> Thanks in advance...
>> Jeff
>>
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-- 
Jeffrey D. Adams
Contractor
OAI, Inc.
In support of:
National Marine Fisheries Service
Office of Protected Resources
1315 East West Hwy, Building SSMC3
Silver Spring, MD 20910
phone: (301) 427-8434
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