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<body class='hmmessage'><div dir='ltr'><p class="MsoNormal">Dear GDAL Developers<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m finding that when
saving a relatively small array (shape =
128,4000,128 ie 128 band x 4000 lines x
128 columns of float data = 256Mb total) to a ENVI file format using the call:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">gdalnumeric.SaveArray(<u>img</u>,strf_out,'ENVI')<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">performance is extremely slow (~260 seconds). When I save the same array to Geotif format using;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">gdalnumeric.SaveArray(<u>img</u>,strf_out,'GTIFF')<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">the operation
takes ~24 seconds which is much more
acceptable. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m currently
using gdal version 1.11.1 . <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My question to
the forum is then -why is there such a
large discrepancy between the performance of the two operations and is there a way
to improve the performance when writing an array to an ENVI file format? <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have tried changing
the GDAL Cache options but performance doesn’t seem to alter. When profiling the code which saves the array
to GeoTIFF format I get the output contained in the attached file timing_savearray_GTIFF.txt. When profiling the code which saves the array
to ENVI format I get the output contained in the attached file timing_savearray_ENVI.txt<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would like to
save the data to ENVI file format. Your
thoughts on this matter would be appreciated.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards <o:p></o:p></p>
<p class="MsoNormal">mike<o:p></o:p></p> </div></body>
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