[gdal-dev] merge with gdalwrap

[Frank Warmerdam]

Steve.Toutant at inspq.qc.ca wrote:
> 
> 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

Steve,

This is a relatively new feature - likely new in 1.6.0.

> 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

I do not believe you should be using a negative for the y pixel size.
In this regard it is a bit different than the way things appear in the
geotransform.

If you want an output image with 30m pixels, you would indeed specify
"-tr 30 30"

If you don't specify, gdalwarp will pick a resolution - possibly based
on the first file, or perhaps the highest resolution file.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent