[gdal-dev] gdalwarp sets nodata value for real data points

[Jerl Simpson]

I've noticed a problem when using gdalwarp to warp netCDF data sets to 
different resolutions.
$ gdalwarp --version
GDAL 1.11.0, released 2014/04/16
It also happens with:
$ gdalwarp --version
GDAL 1.9.2, released 2012/10/08

It makes no difference if I'm warping to a higher, lower or same 
resolution, all the data points from -180 to 90 longitude are set to the 
noData value.
The only points that remain unaffected are those that equal 0.  If I set 
all points that are 0 to 1, then every point <90deg longitude is set to 
the nodata value.

I have seen this before, but specifying the -srcnodata and -dstnodata 
values fixed it in those cases, it seems to have no affect on the 
dataset I'm using now.
One of the versions of the commands I've used, doesn't seem to matter 
which resampling method I use.
$ gdalwarp -r cubicspline -tr 0.1 -0.1 -dstnodata -9999 -srcnodata -9999 
-of netCDF in.nc out.nc

Does anyone have any idea what's going on here?

Input file info (output file info is the same, except (pixel) size changes)

    Driver: netCDF/Network Common Data Format
    Files: in.nc
    Size is 8640, 3432
    Coordinate System is:
    GEOGCS["WGS 84",
         DATUM["WGS_1984",
             SPHEROID["WGS 84",6378137,298.257223563,
                 AUTHORITY["EPSG","7030"]],
             TOWGS84[0,0,0,0,0,0,0],
             AUTHORITY["EPSG","6326"]],
         PRIMEM["Greenwich",0,
             AUTHORITY["EPSG","8901"]],
         UNIT["degree",0.0174532925199433,
             AUTHORITY["EPSG","9108"]],
         AUTHORITY["EPSG","4326"]]
    Origin = (-180.000000000000000,85.000000000114412
    Pixel Size = (0.041666666666700,-0.041666666666700)
    Corner Coordinates:
    Upper Left  (-180.0000000,  85.0000000) (180d 0' 0.00"W, 85d 0' 0.00"N)
    Lower Left  (-180.0000000, -58.0000000) (180d 0' 0.00"W, 58d 0' 0.00"S)
    Upper Right ( 180.0000000,  85.0000000) (180d 0' 0.00"E, 85d 0' 0.00"N)
    Lower Right ( 180.0000000, -58.0000000) (180d 0' 0.00"E, 58d 0' 0.00"S)
    Center      (   0.0000000,  13.5000000) (  0d 0' 0.00"E, 13d30' 0.00"N)
    Band 1 Block=8640x1 Type=Float32, ColorInterp=Undefined
       NoData Value=-9999


Thanks,

Jerl
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