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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks Bryce,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>That’s useful.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I am not planning to cearch using utm coordinates. The main reason I would create a utm geom, was so that I could calculate areas, distances in sq km easily without having to include nested ST_TRANSFORM statements. In this case would it be useful to have another index on the utm?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Cheers<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Vishal<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> postgis-users-bounces@postgis.refractions.net [mailto:postgis-users-bounces@postgis.refractions.net] <b>On Behalf Of </b>Bryce L Nordgren<br><b>Sent:</b> Thursday, August 11, 2011 1:38 PM<br><b>To:</b> PostGIS Users Discussion<br><b>Subject:</b> Re: [postgis-users] spatial indices on two geometry or rast columns<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><br><br><tt><span style='font-size:10.0pt'><a href="mailto:postgis-users-bounces@postgis.refractions.net">postgis-users-bounces@postgis.refractions.net</a> wrote on 08/11/2011 07:16:22 PM:</span></tt><span style='font-size:10.0pt;font-family:"Courier New"'><br><br><tt>> I’d like to transform these layers to UTM (EPSG 32643). I was </tt><br><tt>> thinking of creating a new geometry column for each table and </tt></span><br><tt><span style='font-size:10.0pt'>> ALTER TABLE wards ADD column geom_utm geometry;</span></tt> <br><tt><span style='font-size:10.0pt'>> UPDATE wards SET geom_utm = ST_TRANSFORM(geom,32643);</span></tt> <br><tt><span style='font-size:10.0pt'>> </span></tt> <br><tt><span style='font-size:10.0pt'>> Should I, (and can I) create another gist index on the transformed geometry?</span></tt> <br><br><tt><span style='font-size:10.0pt'>If you're planning on searching using utm coordinates, I'd make another index. If the utm version is just there for reference, I wouldn't bother.</span></tt> <br><br><tt><span style='font-size:10.0pt'>> The same qn applies on a raster table I have called srtm_table – </span></tt><span style='font-size:10.0pt;font-family:"Courier New"'><br><tt>> should I and can I add </tt></span><br><tt><span style='font-size:10.0pt'>> - a new ‘rast’ column called rast_utm with transformed SRID</span></tt><span style='font-size:10.0pt;font-family:"Courier New"'><br><tt>> in similar fashion above, and then add a gist index on the rast_utm column?</tt></span> <br><tt><span style='font-size:10.0pt'>> </span></tt> <br><tt><span style='font-size:10.0pt'>> CREATE INDEX “srtm_table_rast_gist_idx” ON “public”.”srtm_table” </span></tt><span style='font-size:10.0pt;font-family:"Courier New"'><br><tt>> USING GIST (st_convexhull(rast_utm));</tt></span> <br><br><tt><span style='font-size:10.0pt'>This isn't really a different question than the above, since st_convexhull(raster) produces a geometry. :) I'd say the same thing: if you're going to search using utm coordinates, make a utm index; otherwise, no.</span></tt> <br><br><br><tt><span style='font-size:10.0pt'>Bryce</span></tt><o:p></o:p></p></div></body></html>