<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:garamond,new york,times,serif;font-size:12pt;color:#033d21;"><br><div> Hi all, First post but have been lurking for a long time.<br><br>In the process of migrating some geoprocessing procedures over to our open source stack, I came across a difference in results from postgis' st_union vs. arcgis' dissolve. From what I can tell these functions should be synonymous in theory, despite their naming. (?)<br><br>It seems like st_union is not doing a "clean" union, some slivers are remaining. <br><br>Original parcel fabric: <a href="http://quimby.ca/original.jpg">http://quimby.ca/original.jpg<br></a>Dissolved by ArcGIS: <a href="http://quimby.ca/dissolved_by_arcgis.jpg">http://quimby.ca/dissolved_by_arcgis.jpg</a><br>st_union by postgis: <a
href="http://quimby.ca/dissolved_by_postgis.jpg">http://quimby.ca/dissolved_by_postgis.jpg<br></a><br>The input to both functions was the same table in postgis. I am defining the geometry simply as <span style="font-family: Courier New,courier,monaco,monospace,sans-serif;">select st_union(current_assessment_parcel.the_geom) AS the_geom<br><br><span style="font-family: garamond,new york,times,serif;">Postgresql 8.4.1</span><br style="font-family: garamond,new york,times,serif;"><span style="font-family: garamond,new york,times,serif;">Postgis 1.4<br><br>Is this simply a difference in tolerance? or am I seeing something else here.<br><br>Thanks,<br>Lee.<br><br></span></span></div>
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