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<p class="MsoNormal">I have a simple LINE-Geometry and a POINT, that I want to query, if it intersects the line.<o:p></o:p></p>
<p class="MsoNormal">The result ist, that ST_Intersects gives „FALSE“, and ST_Distance gives „0“. So, this is contradictory. An analysis with JTS shows, that there is a distance of
<span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#242729;background:white">
6.611191059663252E-13.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#242729;background:white">Should ST_Distance not also return this result?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#242729;background:white"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#242729;background:white">Here are the SQL-Statements:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#242729;background:white"><o:p> </o:p></span></p>
<p class="MsoNormal">WITH point1 as<o:p></o:p></p>
<p class="MsoNormal">(Select ST_GeomFromWKB('\x0101000020167A0000B0A13497E151E5C0E386CC0EACF50D41', 31254) as geom),<o:p></o:p></p>
<p class="MsoNormal">line1 as<o:p></o:p></p>
<p class="MsoNormal">(select ST_GeomFromWKB('\x0102000020167A000002000000000000003952E5C00000005012F60D4100000000AF51E5C0000000E070F50D41', 31254) as geom)<o:p></o:p></p>
<p class="MsoNormal">select ST_Intersects(line1.geom, point1.geom), ST_Distance(line1.geom, point1.geom),<o:p></o:p></p>
<p class="MsoNormal">ST_AsText(ST_Intersection(line1.geom, point1.geom)),<o:p></o:p></p>
<p class="MsoNormal">ST_AsText(ST_ShortestLine(line1.geom, point1.geom))<o:p></o:p></p>
<p class="MsoNormal">from<o:p></o:p></p>
<p class="MsoNormal">line1, point1;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Even when I try to Snap the point to the line-geometry, it does not work:<o:p></o:p></p>
<p class="MsoNormal">WITH point1 as<o:p></o:p></p>
<p class="MsoNormal">(Select ST_GeomFromWKB('\x0101000020167A0000B0A13497E151E5C0E386CC0EACF50D41', 31254) as geom),<o:p></o:p></p>
<p class="MsoNormal">line1 as<o:p></o:p></p>
<p class="MsoNormal">(select ST_GeomFromWKB('\x0102000020167A000002000000000000003952E5C00000005012F60D4100000000AF51E5C0000000E070F50D41', 31254) as geom)<o:p></o:p></p>
<p class="MsoNormal">select ST_Intersects(line1.geom, ST_ClosestPoint(line1.geom, point1.geom)), ST_Distance(line1.geom, ST_ClosestPoint(line1.geom, point1.geom)),<o:p></o:p></p>
<p class="MsoNormal">ST_AsText(ST_Intersection(line1.geom, ST_ClosestPoint(line1.geom, point1.geom))),<o:p></o:p></p>
<p class="MsoNormal">ST_AsText(ST_ShortestLine(line1.geom, ST_ClosestPoint(line1.geom, point1.geom)))<o:p></o:p></p>
<p class="MsoNormal">from<o:p></o:p></p>
<p class="MsoNormal">line1, point1;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I know about the limitations of floating-point-operations (see discussion here:
<a href="https://stackoverflow.com/questions/60298412/wrong-result-using-st-intersection-with-postgis/">
https://stackoverflow.com/questions/60298412/wrong-result-using-st-intersection-with-postgis/</a>), but ST_Distance should give a result different than 0, right?<o:p></o:p></p>
<p class="MsoNormal">Is this a bug in the ST_Distance-function (and probalby in the ST_ClosestPoint-function)?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<span style="font-size:11.5pt;font-family:"Arial",sans-serif;color:#242729">I tested this with postgres 9.6.15 and postgis 2.4<o:p></o:p></span></p>
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<span style="font-size:11.5pt;font-family:"Arial",sans-serif;color:#242729">and also with<o:p></o:p></span></p>
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<span style="font-size:11.5pt;font-family:"Arial",sans-serif;color:#242729">postgres 12.1 and postgis 3.0, same results.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Didi<o:p></o:p></p>
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