On 15/07/15 14:18, Even Rouault wrote:
On Wednesday 15 July 2015 10:21:54 Homme Zwaagstra wrote:
>> Hello,
>>
>> I've got the following raster exported from GRASS using `r.out.gdal`:
>>
>> gdalinfo ppp-2015.tif
>> Driver: GTiff/GeoTIFF
>> Files: ppp-2015.tif
>> ppp-2015.tif.aux.xml
>> Size is 432017, 216009
>> Coordinate System is:
>> GEOGCS["WGS 84",
>> DATUM["WGS_1984",
>> SPHEROID["WGS 84",6378137,298.257223563,
>> AUTHORITY["EPSG","7030"]],
>> AUTHORITY["EPSG","6326"]],
>> PRIMEM["Greenwich",0],
>> UNIT["degree",0.0174532925199433],
>> AUTHORITY["EPSG","4326"]]
>> Origin = (-180.000000000000000,90.000000000000000)
>> Pixel Size = (0.000833300541414,-0.000833298612558)
>> Metadata:
>> AREA_OR_POINT=Area
>> Image Structure Metadata:
>> COMPRESSION=DEFLATE
>> INTERLEAVE=BAND
>> Corner Coordinates:
>> Upper Left (-180.0000000, 90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"N)
>> Lower Left (-180.0000000, -90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"S)
>> Upper Right ( 180.0000000, 90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"N)
>> Lower Right ( 180.0000000, -90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"S)
>> Center ( 0.0000000, 0.0000000) ( 0d 0' 0.01"E, 0d 0' 0.01"N)
>> Band 1 Block=256x256 Type=Float32, ColorInterp=Gray
>> NoData Value=nan
>> Metadata:
>> COLOR_TABLE_RULES_COUNT=5
>> COLOR_TABLE_RULE_RGB_0=0.000000e+00 1.681282e+03 255 255 0 0 255 0
>> COLOR_TABLE_RULE_RGB_1=1.681282e+03 3.362563e+03 0 255 0 0 255 255
>> COLOR_TABLE_RULE_RGB_2=3.362563e+03 5.043845e+03 0 255 255 0 0 255
>> COLOR_TABLE_RULE_RGB_3=5.043845e+03 6.725127e+03 0 0 255 255 0 255
>> COLOR_TABLE_RULE_RGB_4=6.725127e+03 8.406408e+03 255 0 255 255 0 0
>> Generated_with=GRASS GIS 7.0.0
>>
>> As you can see the NoData is set to `nan`. However, within the data
it is
>> actually `-nan`:
>>
>> gdallocationinfo ppp-2015.tif -wgs84 42.0776 30.9305
>> Report:
>> Location: (266503P,70886L)
>> Band 1:
>> Value: -nan
>>
>> I have tried to force the NoData to `-nan` as follows but with no joy:
>>
>> gdal_translate -a_nodata '-nan' -of VRT ppp-2015.tif ppp-2015.vrt
>>
>> gdalinfo ppp-2015.vrt
>> Driver: VRT/Virtual Raster
>> Files: ppp-2015.vrt
>> /data/data/ppp_v2c_2015/ppp-2015.tif
>> Size is 432017, 216009
>> Coordinate System is:
>> GEOGCS["WGS 84",
>> DATUM["WGS_1984",
>> SPHEROID["WGS 84",6378137,298.257223563,
>> AUTHORITY["EPSG","7030"]],
>> AUTHORITY["EPSG","6326"]],
>> PRIMEM["Greenwich",0],
>> UNIT["degree",0.0174532925199433],
>> AUTHORITY["EPSG","4326"]]
>> Origin = (-180.000000000000000,90.000000000000000)
>> Pixel Size = (0.000833300541414,-0.000833298612558)
>> Metadata:
>> AREA_OR_POINT=Area
>> Image Structure Metadata:
>> INTERLEAVE=BAND
>> Corner Coordinates:
>> Upper Left (-180.0000000, 90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"N)
>> Lower Left (-180.0000000, -90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"S)
>> Upper Right ( 180.0000000, 90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"N)
>> Lower Right ( 180.0000000, -90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"S)
>> Center ( 0.0000000, 0.0000000) ( 0d 0' 0.01"E, 0d 0' 0.01"N)
>> Band 1 Block=128x128 Type=Float32, ColorInterp=Gray
>> NoData Value=nan
>> Metadata:
>> COLOR_TABLE_RULES_COUNT=5
>> COLOR_TABLE_RULE_RGB_0=0.000000e+00 1.681282e+03 255 255 0 0 255 0
>> COLOR_TABLE_RULE_RGB_1=1.681282e+03 3.362563e+03 0 255 0 0 255 255
>> COLOR_TABLE_RULE_RGB_2=3.362563e+03 5.043845e+03 0 255 255 0 0 255
>> COLOR_TABLE_RULE_RGB_3=5.043845e+03 6.725127e+03 0 0 255 255 0 255
>> COLOR_TABLE_RULE_RGB_4=6.725127e+03 8.406408e+03 255 0 255 255 0 0
>> Generated_with=GRASS GIS 7.0.0
>>
>> Even editing the VRT to contain `<NoDataValue>-nan</NoDataValue>`
yields a
>> positive nan value in gdalinfo.
>>
>> This looks like it might be a GDAL bug to me? Is there a way I can
specify
>> `-nan` as the NODATA value for this dataset without regenerating it
>> (it's quite
>> large)?
>
> Hi Homme,
>
> I wasn't aware of this negative not a number variation. Could you
create a
> ticket with a small extract of the dataset so as to inspect the
hexadecimal
> representation of this -nan value ?
Thanks Even,
I have submitted <https://trac.osgeo.org/gdal/ticket/6036> with an
attached TIFF
infested with `-nan` values.
While researching this I cam across this question
<http://stackoverflow.com/q/3772835> which might contain some information of
interest.
Let me know if I can do anything else to help.
Best regards,
Homme
>
> Even
>
>
>>
>> Many thanks,
>>
>> Homme
>>
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>
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