gdalwarp -srcnodata -3.4028234663852886e+38 \
EstRN.img EstSh.img icu.tif
I thought I must launch gdalwrap once for each file. Didn't know I could
specify several input files
I think I need to specify the extent and the resolution.
- Is the resolution is the pixel size get by gdalinfo?
- The Pixel Size is not the same for all images. Per example I got
(30.000000000000099,-30.000000000000103)
and
this for another image
Pixel Size = (30.000000000000000,-30.000000000000000)
What will append if I specify -tr 30 -30 as resolution in this case
thanks
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
[email protected]
http://www.inspq.qc.ca
Frank Warmerdam <[email protected]>
30/07/2009 02:19 PM
A
[email protected]
cc
[email protected]
Objet
Re: [gdal-dev] merge with gdalwrap
[email protected] wrote:
>
> 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)?
Steve,
Yes, gdalwarp will overlay valid new data over existing data with the
last gdalwarp overlaying previous 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.
If you pass an output file to gdalwarp and it already exists then it
will be mosaiced into. If the output file does not already exist
then one is created. This is different than gdal_translate which
always creates a new 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
Well, it doesn't mention EstSH.img - so no it does not seem
to be the same thing. If you did:
gdalwarp -srcnodata -3.4028234663852886e+38 \
EstRN.img EstSh.img icu.tif
then it should be pretty similar. There are subtle differences
of course.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam,
[email protected]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
_______________________________________________
gdal-dev mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/gdal-dev
