<div dir="ltr">You can use the map algebra function combined with Common Table expressions.<div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, May 9, 2017 at 4:20 AM, David Westcott <span dir="ltr"><<a href="mailto:david.westcott@uk.rsagroup.com" target="_blank">david.westcott@uk.rsagroup.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal">Dear Post GIS Users<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Is there a way in PostGIS of applying a formula to more than two Raster layers?<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">For example, I want to derive a new Raster Layer calculated as follows:<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Constant1 x Layer1 x (Layer2 ^ Constant2) + Constant3 x Layer3 x (Layer4 ^ Constant4) + Constant5 x Layer5 x (Layer6 ^ Constant6)<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Where Constant1, Constant2, Constant3, Constant4, Constant5 & Constant6 are fixed constants.<u></u><u></u></p>
<p class="MsoNormal"> Layer1, Layer2, Layer3, Layer4, Layer5 & Layer6 are already derived Raster Layers.<u></u><u></u></p>
<p class="MsoNormal"> The ‘^’ sign represents raised to the power of. (i.e. 3^2 = 9).<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">How would I apply such a formula in PostGIS?<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Kind Regards<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">David Westcott<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
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