[gdal-dev] near identical files being treated differently

[Ken Mankoff]

Hello,

I have two near-identical files available at:

wget https://portal.nccs.nasa.gov/GISS_modelE/modelE_input_data/GLMELT_4X5.OCN.nc

wget https://portal.nccs.nasa.gov/GISS_modelE/modelE_input_data/GLMELT_144X90_gas.OCN.nc

They differ only in their dimensions:

$ diff <(ncdump -h GLMELT_4X5.OCN.nc) <(ncdump -h GLMELT_144X90_gas.OCN.nc)|cat -n
     1  1c1
     2  < netcdf GLMELT_4X5.OCN {
     3  ---
     4  > netcdf GLMELT_144X90_gas.OCN {
     5  3,4c3,4
     6  <       lon = 72 ;
     7  <       lat = 46 ;
     8  ---
     9  >       lon = 144 ;
    10  >       lat = 90 ;


However, "galinfo" sees them differently, and therefore they are treated very differently in, for example, QGIS.


$ diff <(gdalinfo GLMELT_4X5.OCN.nc) <(gdalinfo GLMELT_144X90_gas.OCN.nc)|cat -n
     1  2,3c2,6
     2  < Files: GLMELT_4X5.OCN.nc
     3  < Size is 72, 46
     4  ---
     5  > Files: GLMELT_144X90_gas.OCN.nc
     6  >        GLMELT_144X90_gas.OCN.nc.aux.xml
     7  > Size is 144, 90
     8  > Origin = (-180.000000000000000,90.000000000000000)
     9  > Pixel Size = (2.500000000000000,-2.000000000000000)
    10  8,13c11,18
    11  < Upper Left  (    0.0,    0.0)
    12  < Lower Left  (    0.0,   46.0)
    13  < Upper Right (   72.0,    0.0)
    14  < Lower Right (   72.0,   46.0)
    15  < Center      (   36.0,   23.0)
    16  < Band 1 Block=72x1 Type=Float32, ColorInterp=Undefined
    17  ---
    18  > Upper Left  (-180.0000000,  90.0000000) 
    19  > Lower Left  (-180.0000000, -90.0000000) 
    20  > Upper Right ( 180.0000000,  90.0000000) 
    21  > Lower Right ( 180.0000000, -90.0000000) 
    22  > Center      (   0.0000000,   0.0000000) 
    23  > Band 1 Block=144x1 Type=Float32, ColorInterp=Undefined
    24  >   Min=0.000 Max=1.000 
    25  >   Minimum=0.000, Maximum=1.000, Mean=0.018, StdDev=0.134
    26  16a22,25
    27  >     STATISTICS_MAXIMUM=1
    28  >     STATISTICS_MEAN=0.018364197530864
    29  >     STATISTICS_MINIMUM=0
    30  >     STATISTICS_STDDEV=0.13426449188044


That is, the larger file contains key info:

Origin = (-180.000000000000000,90.000000000000000)
Pixel Size = (2.500000000000000,-2.000000000000000)

Which then generates correct Corner Coordinates.

Given that the 'ncdump' of the two files is identical (except size), can someone clarify what I'm doing wrong here?

Thanks,

  Ken Mankoff