[Qgis-user] No data value in Raster Merge not working

[Etienne Tourigny]

I can confirm that the target nodata values are set to zero (instead of
"nodata").

This can be solved by adding -a_nodata <nodata> manually to the command, in
which case the valeus are set to "nodata" and therefore transparent.

e.g. instead of
gdal_merge.py -n 126 -of GTiff -o
/data/src/qgis/qgis-master/tests/testdata/tmp1.tif
/data/src/qgis/qgis-master/tests/testdata/landsat.tif
the command should be
gdal_merge.py -n 126 -a_nodata 126 -of GTiff -o
/data/src/qgis/qgis-master/tests/testdata/tmp1.tif
/data/src/qgis/qgis-master/tests/testdata/landsat.tif

Can you confirm this works for you? If so, I could fix this for future
releases.
Although, there should probably be an option for this?

Etienne


On Fri, Dec 6, 2013 at 11:36 AM, Harish <harry.om2000 at gmail.com> wrote:

> Dear List!
> Has this discussion made previously in list or I am wrong at my point
> described?
> or communication gap due to poor English?
>
> I want to repeat:
> If we use 'No data value' as zero by selecting the check box in
> Raster>Miscellaneous>Merge operation, it gives black color in no data
> region of output image. We can temporarily see the no data portions
> transparent by putting 'Additional no data value as zero in layer
> Properties>Transparency but after removing it from project whenever image
> is loaded again, it gives blackish no data areas.
>
> In Raster>Extraction>clipper operation it works fine and no data areas in
> output image remains transparent/white always.
>
> Using QGIS2.0.1 win7 32 bit
>
> Regards
>
>
>
> On Thu, Nov 28, 2013 at 6:38 PM, Harish <harry.om2000 at gmail.com> wrote:
>
>> Correction!
>> Even after these message/behavior, results come in the target path/name,
>> but with black color in no data areas.
>> Regards
>>
>>
>>
>> <http://www.nird.org.in>
>>
>
>
>
> --
> Harish Kumar Solanki, Assistant Professor
> National Institute of Rural Development (NIRD),
> Ministry of Rural Development, Government of India
> Jaipur, Rajasthan, India- Pin-302006
>
> Geo_Coordinates (Office): 26.92162 N, 75.78921 E
>
> Email- hksolanki at nird.gov.in, harry.om2000 at gmail.com,
> Tele-Fax-0141-2209905, Mo.- 09214446732, 09414291732
> Website-  http://www.nird.org.in, http://watershed.rajasthan.gov.in/<http://www.nird.org.in>
> LinkedIn: www.linkedIn.com/in/hksolanki
>  <http://www.nird.org.in>
>
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