Jay,<br><br>Can you provide a sample file that gives this error?<br><br><div class="gmail_quote">On Tue, Feb 22, 2011 at 1:56 AM, Jay Jennings <span dir="ltr"><<a href="mailto:Jennings.Jay@geoeye.com">Jennings.Jay@geoeye.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div link="blue" vlink="purple" lang="EN-US"><div><p class="MsoNormal">Hello list,</p><p class="MsoNormal">
(using GDAL 1.8.0) I am trying to create a 32:1 down-sampled overview of a GeoTiff satellite image. My first thought was gdal_translate, with args such as “-outsize 3.125% 3.125%”… which produces surprisingly high quality given the absence of a resampling option. However I’m looking for a downsampling scheme that creates a result pixel by averaging all relevant source pixels (I know, for 32:1 downsample, that means 1024 source pixels for each result pixel !) with the hope of an output that is not “speckled” or “grainy” insofar as possible.</p>
<p class="MsoNormal"> </p><p class="MsoNormal">I also looked at gdaladdo, which does have the “-r average” resampling option… the guidance at <a href="http://gdal.org" target="_blank">gdal.org</a> seems to suggest that it can produce a 32:1 GeoTIFF external overview with a command like this:</p>
<p class="MsoNormal"> </p><p class="MsoNormal">gdaladdo -r average -ro XXXXX.tif 32</p><p class="MsoNormal"> </p><p class="MsoNormal">But that produces a surprising error message, namely:</p><p class="MsoNormal">ERROR 4: `XXXXX.tif.ovr' does not exist in the file system, and is not recognised as a supported dataset name.</p>
<p class="MsoNormal"> </p><p class="MsoNormal">Am I barking up the wrong tree with gdaladdo for this purpose ? Anybody have any suggestions for highest-quality down-sampling ? Thanks in advance.</p><p class="MsoNormal"> </p>
<font color="#888888"><p class="MsoNormal">--Jay Jennings</p></font></div></div><br>_______________________________________________<br>
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