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<p class="MsoNormal"><span style="color:#1F497D">Hi Carl, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I may be reading too much into your message, but my spidey sense tells me you might be using ST_Value inside a loop to get values to put in an equation (or to evaluate thresholds), thereby constructing an output
raster. If this is the case, a more efficient way to proceed may be to use ST_MapAlgebra (for equations), or ST_Reclass (for thresholds). No muss no fuss.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Hope that helps,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Bryce<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<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@lists.osgeo.org [mailto:postgis-users-bounces@lists.osgeo.org]
<b>On Behalf Of </b>Albury, Carl -FS<br>
<b>Sent:</b> Tuesday, April 21, 2015 10:18 AM<br>
<b>To:</b> postgis-users@lists.osgeo.org<br>
<b>Subject:</b> Re: [postgis-users] ST_Value on tiled raster<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi<o:p></o:p></p>
<p class="MsoNormal">I’m new to PostGIS so please bear with me.<o:p></o:p></p>
<p class="MsoNormal">I’m working with MODIS data that I tiled using the auto tile switch in raster2pgsql resulting in 13250 82x94 tiles.<o:p></o:p></p>
<p class="MsoNormal">When I try to query for pixel values using ST_Value, such as:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">SELECT<o:p></o:p></p>
<p class="MsoNormal"> ST_Value(rast, 2, 1,1) -- multiband raster<o:p></o:p></p>
<p class="MsoNormal">FROM<o:p></o:p></p>
<p class="MsoNormal"> MODIS_test;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I get a value for each tile, not for each pixel (I assume the value is for the first pixel in the tile?).<o:p></o:p></p>
<p class="MsoNormal">If I want to query each pixel do I need to loop through each tile and have a sub loop for each pixel in that tile? If so I can’t figure out the syntax to designate the tiles vs pixels.<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal">Thanks very much,<o:p></o:p></p>
<p class="MsoNormal">Carl<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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