[Gdal-dev] gdal_merge.py / gdalwarp usage issues

[Izzy]

Hi,

I am new to this area and I have some experience programming on Python.

I tried to use gdalwarp with no much success to compose satellite Geotiff
images so far.  I would like to use it but I can't find explanations on how
to use many of the options.
I wouldn't mind using gdal_merge.py if I can get the correct results.
I need to stitch together satellite images received from various satellites
that have been converted into GeoTiffs. The composite image needs to keep
same resolution of original images.  So, I tried first to use gdal_merge.py,
but since many areas from original tiffs are black, I keep getting portions
of some satellite pictures covered by the black portion of their neighbor
maps.  Besides, the colors in the final image look like very fainted
compared to the original images.

I can't figure out how to solve this two issues neither with gdal_merge.py
nor with gdal_warp.

This is what I used for gdal_merge.py:
gdal_merge.py -o $ofn -v -n 0 AS_*.tif EP_*.tif EU_*.tif US_*.tif IO_*.tif
where $ofn= output file name.  Only one input image per region is available
at any given time.  I used the * to avoid having to write a very long
portion of the map name which includes a date/time stamp.

This is what I used for gdal_warp:
gdalwarp -of GTiff EP_*tif $ofn
gdalwarp -of GTiff US_*tif $ofn
gdalwarp -of GTiff EU_*tif $ofn
gdalwarp -of GTiff IO_*tif $ofn
gdalwarp -of GTiff AS_*tif $ofn

I get errors after the second image is warped.  I did try sizing the output
image using "-tr <out_size>" with no luck
out_size=12000 800 since each image was 2400 800

Does anyone know where I could find examples using all the options for
merge_gdal.py and gdalwarp?  I visited the obvious gdal sites I found while
searching with Google.

Thanks
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