[gdal-dev] Gdal doesn't see NaN values as NoData?
even.rouault at spatialys.com
Wed May 5 14:49:20 PDT 2021
> a) Why does gdalinfo not report the presence of nan? Meaning: how do I know when I will need to invoke (b)?
It doesn't report nan as the nodata value, because the file lacks the
GDAL_NODATA tiff tag set at "nan". So the issue is on the producer side.
> b) What do I need to do so that applications will use nan as nodata?
gdalwarp -dstnodata nan ...
or if you want to remap nan to some other value
gdalwarp -dstnodata -9999 ...
In most cases, you'd need to explicitly add the srcnodata value with
-srcnodata nan , but nan is a special case. When gdalwarp finds a pixel
at NaN value, be it the declared nodata value or not, it assumes this is
nodata, hence you can omit -srcnodata nan. Wouldn't be true if 0 or some
other value was the undeclared nodata value.
I've some doubt that it is produced by GEE. Seems move to come from Esri
$ tiffinfo NDVI1984.tif
Tag 42112: <GDALMetadata>
<Item name="PyramidResamplingType" domain="Esri">NEAREST</Item>
<Item name="DESCRIPTION" sample="0" role="description">NDVI</Item>
My software is free, but my time generally not.
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