<br><tt><font size=2>gdalwarp -srcnodata -3.4028234663852886e+38 \<br>
EstRN.img EstSh.img icu.tif<br>
</font></tt>
<br><font size=2 face="sans-serif">I thought I must launch gdalwrap once
for each file. Didn't know I could specify several input files</font>
<br>
<br><font size=2 face="sans-serif">I think I need to specify the extent
and the resolution.</font>
<br><font size=2 face="sans-serif">- Is the resolution is the pixel size
get by gdalinfo?</font>
<br>
<br><font size=2 face="sans-serif">- The Pixel Size is not the same for
all images. Per example I got </font>
<br><font size=2 face="sans-serif"> (30.000000000000099,-30.000000000000103)</font>
<br><font size=2 face="sans-serif">and </font>
<br><font size=2 face="sans-serif">this for another image</font>
<br><font size=2 face="sans-serif">Pixel Size = (30.000000000000000,-30.000000000000000)</font>
<br>
<br><font size=2 face="sans-serif">What will append if I specify -tr 30
-30 as resolution in this case</font>
<br>
<br><font size=2 face="sans-serif">thanks</font>
<br><font size=2 face="sans-serif">Steve<br>
</font><font size=3 color=#0066ff><i>Steve Toutant, M. Sc.</i></font><font size=3><br>
Analyste en géomatique<br>
Secteur environnement<br>
Direction des risques biologiques, environnementaux et occupationnels<br>
Institut national de santé publique du Québec<br>
945, avenue Wolfe<br>
Québec, Qc G1V 5B3 </font>
<p><font size=3>Tél.: (418) 650-5115 #5281<br>
Fax.: (418) 654-3144</font><font size=3 color=blue><u><br>
</u></font><a href=mailto:steve.toutant@inspq.qc.ca><font size=3 color=blue><u>steve.toutant@inspq.qc.ca</u></font></a><font size=3 color=blue><u><br>
</u></font><a href=http://www.inspq.qc.ca/><font size=3 color=blue><u>http://www.inspq.qc.ca</u></font></a>
<p><font size=3> </font>
<p>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>Frank Warmerdam <warmerdam@pobox.com></b>
</font>
<p><font size=1 face="sans-serif">30/07/2009 02:19 PM</font>
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<div align=right><font size=1 face="sans-serif">A</font></div>
<td><font size=1 face="sans-serif">Steve.Toutant@inspq.qc.ca</font>
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<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td><font size=1 face="sans-serif">gdal-dev@lists.osgeo.org</font>
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<td>
<div align=right><font size=1 face="sans-serif">Objet</font></div>
<td><font size=1 face="sans-serif">Re: [gdal-dev] merge with gdalwrap</font></table>
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<br><tt><font size=2>Steve.Toutant@inspq.qc.ca wrote:<br>
> <br>
> Hi,<br>
> I tried gdal_merge.py but I got a memory Error because I use the -n
<br>
> nodata value option. Several threads sugest that I must use gdalwrap
<br>
> instead.<br>
> This behavior of gdal_merge.py is very important to me in this <br>
> particular case<br>
> "In areas of overlap, the last image will be copied over earlier
ones".<br>
> <br>
> Does gdalwrap has the same behavior? (I ask because it is difficult
to <br>
> test and validate with my data)?<br>
<br>
Steve,<br>
<br>
Yes, gdalwarp will overlay valid new data over existing data with the<br>
last gdalwarp overlaying previous data.<br>
<br>
> Also, the doc says "Mosaicing into an existing output file is
supported <br>
> if the output file already exists."<br>
> But how? What is the option to append data? When launching a command
for <br>
> another image it says that I must delete the output file.<br>
<br>
If you pass an output file to gdalwarp and it already exists then it<br>
will be mosaiced into. If the output file does not already exist<br>
then one is created. This is different than gdal_translate which<br>
always creates a new file.<br>
<br>
> I would appreciate if someone could validate if this<br>
> gdalwarp -srcnodata -3.4028234663852886e+38 -dstnodata <br>
> -3.4028234663852886e+38 -of "GTiff" EstRN.img icu.tif<br>
> <br>
> is the equivalent of this<br>
> gdal_merge.py -n -3.4028234663852886e+38 -o icu.tif -of "GTiff"
<br>
> EstRN.img EstSh.img<br>
<br>
Well, it doesn't mention EstSH.img - so no it does not seem<br>
to be the same thing. If you did:<br>
<br>
gdalwarp -srcnodata -3.4028234663852886e+38 \<br>
EstRN.img EstSh.img icu.tif<br>
<br>
then it should be pretty similar. There are subtle differences<br>
of course.<br>
<br>
Best regards,<br>
-- <br>
---------------------------------------+--------------------------------------<br>
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com<br>
light and sound - activate the windows | http://pobox.com/~warmerdam<br>
and watch the world go round - Rush | Geospatial Programmer
for Rent<br>
<br>
</font></tt>
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