[GRASS-user] Help with export netCDF file

[Thomas Adams]

Hi all,

I really don't have a problem with exporting a netCDF file from GRASS 8.4,
but because of the intended use of the output file, I need to have variable
name defined specifically, instead of the generic Band1:

ncdump -h sac_UZTWM.nc

netcdf sac_UZTWM {
dimensions:
x = 2698 ;
y = 2427 ;
variables:
double Band1(y, x) ;
Band1:long_name = "GDAL Band Number 1" ;
Band1:_FillValue = -999. ;
Band1:grid_mapping = "lambert_conformal_conic" ;
Band1:COLOR_TABLE_RULES_COUNT = 255 ;
Band1:COLOR_TABLE_RULE_RGB_0 = "0.000000e+00 5.496153e-01 68 1 84 68 2 86" ;
Band1:COLOR_TABLE_RULE_RGB_1 = "5.496153e-01 1.099231e+00 68 2 86 69 4 87" ;
Band1:COLOR_TABLE_RULE_RGB_2 = "1.099231e+00 1.648846e+00 69 4 87 69 5 89" ;
Band1:COLOR_TABLE_RULE_RGB_3 = "1.648846e+00 2.199863e+00 69 5 89 70 7 90" ;
Band1:COLOR_TABLE_RULE_RGB_4 = "2.199863e+00 2.749479e+00 70 7 90 70 8 92" ;
Band1:COLOR_TABLE_RULE_RGB_5 = "2.749479e+00 3.299094e+00 70 8 92 70 10 93"
;
Band1:COLOR_TABLE_RULE_RGB_6 = "3.299094e+00 3.848709e+00 70 10 93 70 11
94" ;
Band1:COLOR_TABLE_RULE_RGB_7 = "3.848709e+00 4.398325e+00 70 11 94 71 13
96" ;

I need what I have below, using Climate Data Operators (cdo)...

cdo -chname,Band1,sac_UZTWM sac_UZTWM.nc sac_UZTWM.nc.test

I can change the variable name, which is exactly what I need:

ncdump -h sac_UZTWM.nc
netcdf sac_UZTWM {
dimensions:
x = 2698 ;
y = 2427 ;
variables:
double x(x) ;
x:standard_name = "projection_x_coordinate" ;
x:long_name = "x coordinate of projection" ;
x:units = "m" ;
x:axis = "X" ;
double y(y) ;
y:standard_name = "projection_y_coordinate" ;
y:long_name = "y coordinate of projection" ;
y:units = "m" ;
y:axis = "Y" ;
char lambert_conformal_conic ;
lambert_conformal_conic:grid_mapping_name = "lambert_conformal_conic" ;
lambert_conformal_conic:longitude_of_central_meridian = 74. ;
lambert_conformal_conic:false_easting = 0. ;
lambert_conformal_conic:false_northing = 0. ;
lambert_conformal_conic:latitude_of_projection_origin = 23. ;
lambert_conformal_conic:standard_parallel = 33., 45. ;
lambert_conformal_conic:long_name = "CRS definition" ;
lambert_conformal_conic:longitude_of_prime_meridian = 0. ;
lambert_conformal_conic:semi_major_axis = 6378137. ;
lambert_conformal_conic:inverse_flattening = 298.257223563 ;
lambert_conformal_conic:crs_wkt =
"PROJCS[\"unknown\",GEOGCS[\"wgs84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS_1984\",6378137,298.257223563]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]]],PROJECTION[\"Lambert_Conformal_Conic_2SP\"],PARAMETER[\"latitude_of_origin\",23],PARAMETER[\"central_meridian\",74],PARAMETER[\"standard_parallel_1\",33],PARAMETER[\"standard_parallel_2\",45],PARAMETER[\"false_easting\",0],PARAMETER[\"false_northing\",0],UNIT[\"metre\",1,AUTHORITY[\"EPSG\",\"9001\"]],AXIS[\"Easting\",EAST],AXIS[\"Northing\",NORTH]]"
;
lambert_conformal_conic:spatial_ref =
"PROJCS[\"unknown\",GEOGCS[\"wgs84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS_1984\",6378137,298.257223563]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]]],PROJECTION[\"Lambert_Conformal_Conic_2SP\"],PARAMETER[\"latitude_of_origin\",23],PARAMETER[\"central_meridian\",74],PARAMETER[\"standard_parallel_1\",33],PARAMETER[\"standard_parallel_2\",45],PARAMETER[\"false_easting\",0],PARAMETER[\"false_northing\",0],UNIT[\"metre\",1,AUTHORITY[\"EPSG\",\"9001\"]],AXIS[\"Easting\",EAST],AXIS[\"Northing\",NORTH]]"
;
lambert_conformal_conic:GeoTransform = "-1567000 1000 0 2160000 0 -1000 " ;
double sac_UZTWM(y, x) ;
sac_UZTWM:long_name = "GDAL Band Number 1" ;
sac_UZTWM:grid_mapping = "lambert_conformal_conic" ;
sac_UZTWM:_FillValue = -999. ;
sac_UZTWM:missing_value = -999. ;

// global attributes:
:CDI = "Climate Data Interface version 2.4.0 (https://mpimet.mpg.de/cdi)" ;
:Conventions = "CF-1.5" ;
:GDAL = "GDAL 3.9.3, released 2024/10/07 (debug build)" ;
:history = "Tue Feb 25 06:31:46 2025: cdo -chname,Band1,sac_UZTWM
sac_UZTWM.nc sac_UZTWM.nc.test\n",
"Tue Feb 25 06:30:38 2025: GDAL Create(
/media/teaiii/research/pakistan/parameters/sac_UZTWM.nc, ... )" ;
:CDO = "Climate Data Operators version 2.4.0 (https://mpimet.mpg.de/cdo)" ;
}

But how using r.out.gdal can I do this; I tried something that I thought
should work, but I got an error

r.out.gdal -c -m --overwrite input=uztwm at teaiii
output=/media/teaiii/research/pakistan/parameters/sac_UZTWM.nc
format=netCDF nodata=-999

Thank you,
Tom
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