[Gdal-dev] GDAL "ignores" explicitly defined nodata value

orbiter_postmuch dan0225 at sbcglobal.net
Sun Sep 27 06:15:46 EDT 2009

NOTE-Since people' responses come through the mailing list only, expect a
line of new topics in a row by me to flood (by "flood" I mean 4 topics in a
row by the same author) the forum.

After successfully building the .vrt and translating it to .img, I opened
the file and found that the white (nodata) values were copied over valid
data. I then tried this:

gdal_translate -of PNG -a_nodata 253 file_list.vrt MOD44W.png

The nodata value in the map was specified as 253 in the official PDF. Still,
no luck.
Here is an example of the tiling:


Also, when I checked the .vrt, the size was reported as, '<VRTDataset
rasterXSize="91727" rasterYSize="45855">'

Now, a 500 meter/px image would be 86400x43200 pixels. A 250m image would be
172800x86400 pixels. The landmask was 231.7m. The reported size was half the
resolution of the map!
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