Enable NODATA to be set to -nan

[hrz]

The attached TIFF with Float32 datatype contains values that are negative not a number (-nan):

gdallocationinfo negative-nan-example.tif 0 0
Report:
  Location: (0P,0L)
  Band 1:
    Value: -nan

It does not appear to be possible to set specify -nan as the NODATA value e.g:

gdal_translate -a_nodata '-nan' -of VRT negative-nan-example.tif negative-nan-example.vrt

The resulting NODATA value is always unsigned nan.

[hrz]

TIFF file containing -nan values.

[Markus Neteler]

See also gdal-dev posting in

• ​https://lists.osgeo.org/pipermail/gdal-dev/2015-July/042215.html

and related answer in

• ​https://lists.osgeo.org/pipermail/grass-dev/2015-July/075727.html

[hrz]

I have generated rasters using both r.external.out and r.out.gdal built with the GRASS fix referenced above (commit r65602). These create nan values that are successfully interpreted as NODATA by GDAL - thank you!

Interestingly r.out.gdal still outputs the following message which talks about -nan:

Input raster map contains cells with NULL-value (no-data). The value -nan
will be used to represent no-data values in the input map. You can specify
a nodata value with the nodata option.

[Even Rouault]

I understand we can close this ticket.