[postgis-users] Spurious Results using ST_Split

[Jeff Adams - NOAA Affiliate]

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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