[gdal-dev] merge with gdalwrap

[Steve.Toutant at inspq.qc.ca]

Hi,
I tried gdal_merge.py but I got a memory Error because I use the -n nodata 
value option. Several threads sugest that I must use gdalwrap instead.
This behavior of gdal_merge.py is very important to me in this particular 
case
"In areas of overlap, the last image will be copied over earlier ones".

Does gdalwrap has the same behavior? (I ask because it is difficult to 
test and validate with my data)?

Also, the doc says "Mosaicing into an existing output file is supported if 
the output file already exists." 
But how? What is the option to append data? When launching a command for 
another image it says that I must delete the output file.

I would appreciate if someone could validate if this 
gdalwarp -srcnodata -3.4028234663852886e+38 -dstnodata 
-3.4028234663852886e+38 -of "GTiff" EstRN.img icu.tif

is the equivalent of this 
gdal_merge.py -n -3.4028234663852886e+38 -o icu.tif -of "GTiff" EstRN.img 
EstSh.img

It works but maybe some more parameters are important. 

Thanks for your help,
Steve



Steve Toutant, M. Sc.
Analyste en géomatique
Secteur environnement
Direction des risques biologiques, environnementaux et occupationnels
Institut national de santé publique du Québec
945, avenue Wolfe
Québec, Qc G1V 5B3 
Tél.: (418) 650-5115 #5281
Fax.: (418) 654-3144
steve.toutant at inspq.qc.ca
http://www.inspq.qc.ca
 
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