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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>Matt,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>Although I have not worked with multi-band HFA format, I have
experimented fairly extensively with single-band, GDAL-produced, HFA-format
files in ArcGIS 9.3.1 SP1. Maybe my experience will be interesting to you
anyway.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>My experience was that calculating the statistics with GDAL and
with ArcGIS was not equivalent. For example, when I calculated the statistics
with GDAL for integer rasters, they did not show up with a random color
classification in ArcGIS by default. They appeared to use a black-to-white stretch
instead. This was not desirable for categorical data (e.g. landcover values). But
if I calculated the statistics using ArcGIS, they did show up with random
colors.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>Unfortunately I did not take extensive notes on this,
summarizing my experience in my own code with this comment:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # Do not use GDAL to
calculate statistics.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # Even though GDAL
can do it faster than the geoprocessor, we<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # prefer to use the
geoprocessor to maximize the compatibility<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # of the output
raster with ArcGIS. For example, I do not know<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # how to get GDAL to
build an ArcGIS-compatible histogram.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # Without the
histogram ArcGIS defaults to displaying integer<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # rasters using a
black-to-white stretch rather than a unique<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # value classifier
with random colors. ArcGIS users will<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # expect colors; to
get the necessary histogram, we have to<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'> # calculate
statistics with the geoprocessor.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>I also recall there being some other differences, possibly with
floating point files, too. I’m sorry I did not take better notes.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>I found the whole thing a bit bizarre because I thought that
ArcGIS 9.3.1 used GDAL internally to manipulate HFA files. But maybe not in all
circumstances. And 9.3.1 has an ESRI-customized version of GDAL 1.4, so it is
not like they are running the latest GDAL code…<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>Anyway, hope this helps,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#1F497D'>Jason<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
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";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'> gdal-dev-bounces@lists.osgeo.org
[mailto:gdal-dev-bounces@lists.osgeo.org] <b>On Behalf Of </b>Matt Hanneman<br>
<b>Sent:</b> Wednesday, October 20, 2010 4:51 PM<br>
<b>To:</b> gdal-dev@lists.osgeo.org<br>
<b>Subject:</b> [gdal-dev] gdal_merge: stacking and band statistics<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi,<br>
<br>
Can anyone help a newbie? I have been trying to calculate statistics with
gdal_merge when merging/stacking several tiffs together into a HFA format (see
below for syntax). However, when loaded into ArcGIS it reports that there are
no statistics calculated for any of the bands. Will the 'STATISTICS' option not
work when stacking multiple bands? As you can probably tell I am fairly new to
this, so forgive my ignorance.<br>
<br>
gdal_merge -co STATISTICS=YES -v -o "E:/Temp/A2E.img" -of HFA
-separate "A.TIF" "B.TIF" "C.TIF" "D.TIF"
"E.TIF" "F.TIF"<br>
<br>
Thanks,<br>
<br>
Matt <o:p></o:p></p>
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<p class=MsoNormal>-- <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#666666'>Matt
Hanneman</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:#666666'><br>
</span><span style='font-size:9.0pt;font-family:"Tahoma","sans-serif";
color:#666666'>Director of GIS and Remote Sensing<br>
Global Forest Watch Canada<br>
10337 146 St, Edmonton, AB T5N 3A3<br>
Tel: 780-422-5989 Fax: 780-454-5521 <br>
<a href="http://www.globalforestwatch.ca/">www.globalforestwatch.ca</a></span><o:p></o:p></p>
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