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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Hi Gdal,<br>
<br>
I am having some issues with gdal_merge.py. <br>
<br>
When I merge two tifs together, the original nodata value is converted to 0, no matter what that original no data was. Here is my test case:<br>
<br>
Data:<br>
<br>
https://data.linz.govt.nz/x/9iitN4 DEM_BA32_3501_2013<br>
<br>
https://data.linz.govt.nz/x/WLurgo DEM_BA31_3550_2013<br>
<br>
Running gdalinfo on both files reveals a 'nodata' value of -9999. When I view the data as individual files in QGIS, the 'nodata' regions are confirmed as 'nodata' or '-9999' and are rendered transparent.<br>
<br>
Next I run gdal_merge.py:<br>
<br>
gdal_merge.py -o test_merge.tif *.tif<br>
<br>
I also try:<br>
<br>
gdal_merge.py -n -9999 -a_nodata -9999 -o test_merge_wnodata.tif *.tif<br>
<br>
No matter which variation of merge I run, those regions that once contained 'nodata' or '-9999' are converted to '0' and the nodata value is not retained after the merge. When I load the test_merge_wnodata.tif into QGIS, those regions once containing 'nodata',
are now filled with 0 and rendered as such.<br>
<br>
Maybe this is a bug or am I using gdal_merge.py improperly.<br>
<br>
Cheers,<br>
<br>
Ian<br>
<br>
<br>
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