<div dir="auto">You can also build your VRT using QGIS' processing toolbox.</div><div class="gmail_extra"><br><div class="gmail_quote">On Oct 5, 2017 7:26 PM, "Régis Haubourg" <<a href="mailto:regis.haubourg@gmail.com">regis.haubourg@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">GDAL is probably installed on your system, you need it for QGIS :)<div><br></div><div>something like this should do the trick in a linux bash or from the osgeo4w embedded shells (either windows or msys )</div><div class="m_-4922929325503284444gmail-code m_-4922929325503284444gmail-panel m_-4922929325503284444gmail-pdl m_-4922929325503284444gmail-conf-macro m_-4922929325503284444gmail-output-block" style="margin:10px 0px;padding:0px;color:rgb(51,51,51);border:1px solid rgb(204,204,204);overflow:auto;border-radius:3px;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Noto Sans",Ubuntu,"Droid Sans","Helvetica Neue",sans-serif;font-size:14px"><div class="m_-4922929325503284444gmail-codeContent m_-4922929325503284444gmail-panelContent m_-4922929325503284444gmail-pdl" style="margin:0px;padding:0px;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;line-height:20px;overflow:hidden;border-bottom-left-radius:3px;border-bottom-right-radius:3px"><div style="margin:0px;padding:0px"><div id="m_-4922929325503284444gmail-highlighter_27761" class="m_-4922929325503284444gmail-syntaxhighlighter m_-4922929325503284444gmail-sh-default m_-4922929325503284444gmail-nogutter m_-4922929325503284444gmail-bash" style="margin:0px;padding:0px;width:2149px;overflow:auto;font-size:1em"><table border="0" cellpadding="0" cellspacing="0" style="border-radius:0px;background:0px 50%;border:0px;float:none;height:auto;line-height:20px;margin:0px;outline:0px;overflow:visible;padding:0px;vertical-align:baseline;width:2149px;box-sizing:content-box;font-family:Consolas,"Bitstream Vera Sans Mono","Courier New",Courier,monospace;min-height:inherit"><tbody style="border-radius:0px;background:0px 50%;border:0px;float:none;height:auto;line-height:20px;margin:0px;outline:0px;overflow:visible;padding:0px;vertical-align:baseline;width:auto;box-sizing:content-box;min-height:inherit"><tr style="border-radius:0px;background:0px 50%;border:0px;float:none;height:auto;line-height:20px;margin:0px;outline:0px;overflow:visible;padding:0px;vertical-align:baseline;width:auto;box-sizing:content-box;min-height:inherit"><td class="m_-4922929325503284444gmail-code" style="border:0px;background:0px 50%;overflow:visible;border-radius:0px;float:none;height:auto;line-height:20px;outline:0px;padding:0px 0px 0px 15px;vertical-align:baseline;width:2134px;box-sizing:content-box;font-family:Consolas,"Bitstream Vera Sans Mono","Courier New",Courier,monospace;min-height:inherit"><div class="m_-4922929325503284444gmail-container" title="Hint: double-click to select code" style="margin:15px 0px 0px;padding:0px 0px 15px;border-radius:0px;background:0px 50%;border:0px;float:none;height:auto;line-height:20px;outline:0px;overflow:visible;vertical-align:baseline;width:auto;box-sizing:content-box;min-height:inherit;white-space:pre-wrap"><div class="m_-4922929325503284444gmail-line m_-4922929325503284444gmail-number1 m_-4922929325503284444gmail-index0 m_-4922929325503284444gmail-alt2" style="margin:0px;padding:0px 1em 0px 0px;border-radius:0px;background-image:initial;background-position:0px 50%;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;border:0px;float:none;height:auto;line-height:20px;outline:0px;overflow:visible;vertical-align:baseline;width:auto;box-sizing:content-box;min-height:inherit;white-space:nowrap"><code class="m_-4922929325503284444gmail-bash m_-4922929325503284444gmail-plain" style="font-family:Consolas,"Bitstream Vera Sans Mono","Courier New",Courier,monospace;border-radius:0px;background:0px 50%;border:0px;float:none;height:auto;line-height:20px;margin:0px;outline:0px;overflow:visible;padding:0px;vertical-align:baseline;width:auto;box-sizing:content-box;min-height:inherit;color:black">gdalbuildvrt all_ecw.vrt *.tiff -a_srs </code><code class="m_-4922929325503284444gmail-bash m_-4922929325503284444gmail-string" style="font-family:Consolas,"Bitstream Vera Sans Mono","Courier New",Courier,monospace;border-radius:0px;background:0px 50%;border:0px;float:none;height:auto;line-height:20px;margin:0px;outline:0px;overflow:visible;padding:0px;vertical-align:baseline;width:auto;box-sizing:content-box;min-height:inherit;color:blue">"EPSG:yourSridHere"</code></div></div></td></tr></tbody></table></div></div></div></div><div class="gmail_extra">See <a href="http://geoserver.geo-solutions.it/edu/en/raster_data/advanced_gdal/example1.html" target="_blank">http://geoserver.geo-<wbr>solutions.it/edu/en/raster_<wbr>data/advanced_gdal/example1.<wbr>html</a> for instance</div><div class="gmail_extra"><br></div><div class="gmail_extra"><br></div><div class="gmail_extra"><br></div><div class="gmail_extra"><br><div class="gmail_quote">2017-10-05 14:19 GMT+02:00 Patrick Dunford <span dir="ltr"><<a href="mailto:blackwhitekez@gmail.com" target="_blank">blackwhitekez@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
  
    
  
  <div bgcolor="#FFFFFF">
    <p>I probably don't have the technical means to use that.<br>
    </p><div><div class="m_-4922929325503284444gmail-h5">
    <br>
    <div class="m_-4922929325503284444gmail-m_-7824039846924960592moz-cite-prefix">On 06/10/17 01:12, Régis Haubourg
      wrote:<br>
    </div>
    <blockquote type="cite">
      <div dir="ltr">here it is: <a href="http://www.gdal.org/gdal_vrttut.html" target="_blank">http://www.gdal.org/gdal_v<wbr>rttut.html</a>
        <div><br>
        </div>
        <div>you can assemble raster of vector files, apply filters,
          reprojections, build pyramids to avoid fetching the lowest
          resolution data. This is pretty efficient. </div>
        <div><br>
        </div>
        <div>Cheers</div>
        <div>Régis</div>
      </div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">2017-10-05 14:10 GMT+02:00 Patrick
          Dunford <span dir="ltr"><<a href="mailto:blackwhitekez@gmail.com" target="_blank">blackwhitekez@gmail.com</a>></span>:<br>
          <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
            <div bgcolor="#FFFFFF">
              <p>I don't know what this is.<br>
              </p>
              <div>
                <div class="m_-4922929325503284444gmail-m_-7824039846924960592h5"> <br>
                  <div class="m_-4922929325503284444gmail-m_-7824039846924960592m_-8794353157527591599moz-cite-prefix">On
                    06/10/17 01:08, Régis Haubourg wrote:<br>
                  </div>
                  <blockquote type="cite">
                    <div dir="ltr">Hi Patrick ,
                      <div> did you consider using GDAL VRT to avoid
                        opening so much files? </div>
                      <div>In my experience, this works well. </div>
                      <div>Régis</div>
                      <div><br>
                      </div>
                    </div>
                    <div class="gmail_extra"><br>
                      <div class="gmail_quote">2017-10-05 13:48
                        GMT+02:00 Patrick Dunford <span dir="ltr"><<a href="mailto:blackwhitekez@gmail.com" target="_blank">blackwhitekez@gmail.com</a>></span>:<br>
                        <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Some time ago in a
                          discussion of a particular bug a contributor
                          expressed concern that the refresh of
                          background rasters (aerial photography) in
                          Windows was too slow.<br>
                          <br>
                          Maybe this is the reason that recent versions
                          of master appear to be loading all of the
                          background imagery into memory (I use a master
                          from January this year to work around issues
                          with later ones, and that master does not have
                          this feature).<br>
                          <br>
                          Unfortunately if there are a lot of rasters
                          then the memory demand is excessive and
                          unsurprisingly slows down the computer
                          negating any purported benefit of caching.<br>
                          <br>
                          As an example a project I am currently working
                          on has about 900 aerial photo images
                          (GeoJpeg). When the layer is turned on for
                          display, Qgis requires about 46 GB of virtual
                          memory. Since my computer only has 24 GB of
                          physical memory, it is required to dip into
                          the swap space considerably. Even with 60 GB
                          of swap space on an SSD, the swapping needed
                          to refresh the canvas is substantial and
                          dramatically reduces performance resulting in
                          substantial delays. Compare with the January
                          master referred to above which only requires
                          about 7 GB of virtual memory total with the
                          aerial photo layer displayed. The time needed
                          to refresh the canvas is less than 1 second,
                          most of the time.<br>
                          <br>
                          I know that the canvas refresh in Windows with
                          aerial photos can be substantially slower than
                          in Linux. This does not affect me, because I
                          don't use Windows now that I have a stable
                          platform for running an older Linux master
                          alongside the most recent one. What I do know
                          is that the memory demands are making it
                          difficult to evaluate the recent masters. I
                          need some kind of setting to turn this caching
                          off. With the aerial photo layer turned off,
                          the memory usage of the current master is
                          about the same as the old one, and it's much
                          quicker to update.<br>
                          <br>
                          <br>
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                      </div>
                      <br>
                    </div>
                  </blockquote>
                  <br>
                </div>
              </div>
            </div>
          </blockquote>
        </div>
        <br>
      </div>
    </blockquote>
    <br>
  </div></div></div>

</blockquote></div><br></div></div>
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