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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><pre>>I have many different polygons in my database and would like to know if<o:p></o:p></pre><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>there's any way to find out if a polygon has the shape of a circle. I<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>searched both on Google and in the Postgis documentation but couldn't find<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>someone with the same question.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>One thought – use the ST_LineToCurve function and see if it comes back with a circularstring or one of the curved family of geometry types<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>A circle would be a circularstring with 3 points<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><a href="http://postgis.net/docs/manual-2.1/ST_LineToCurve.html">http://postgis.net/docs/manual-2.1/ST_LineToCurve.html</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>e.g.<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>SELECT ST_AsText(ST_LineToCurve(ST_Boundary(ST_Buffer(ST_Point(1,2),10))));<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>--<o:p></o:p></p><p class=MsoNormal>CIRCULARSTRING(11 2,-9 1.99999999999997,11 2)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>SELECT ST_GeometryType(ST_LineToCurve(ST_Boundary(ST_Buffer(ST_Point(1,2),10))));<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>ST_CircularString<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If your geometry has any kind of curve, it should come back different<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>So for example<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>SELECT ST_GeometryType(ST_LineToCurve(ST_GeomFromText('LINESTRING(1 2, 3 4, 5 6, 7 8)')))<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>ST_LineString<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hope that helps,<o:p></o:p></p><p class=MsoNormal>Regina<o:p></o:p></p><p class=MsoNormal><a href="http://www.postgis.us">http://www.postgis.us</a><o:p></o:p></p><p class=MsoNormal>http://postgis.net<o:p></o:p></p></div></body></html>