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How to convert gridded population Ascii file to Netcdf file

Added by muhammad Shoaib over 2 years ago

Hi everyone,
I have a gridded population file in Ascii format and I need it in nc format. I converted the file with the following CDO command:

cdo -f nc -settaxis,2005-01-01,00:00:00,1day -setname,population -input,gridfile.txt population1.nc < pop.txt

could anyone help me please to check the file that what error it has.

The gridfile.txt as follows

gridtype = lonlat
xsize = 360
ysize = 180
xfirst = 0.0
xinc = 1.0
yfirst = 89.5
yinc = 1.0

whereas I downloaded the Ascii file from https://sedac.ciesin.columbia.edu/data/set/gpw-v4-population-density-rev11/data-download

as I needed a single year gridded population data file.
thank you for the help in advance.

Shoaib

Download all files
gridfile.txt (95 Bytes) gridfile.txt grid description file
population1.nc (258 KB) population1.nc Output file
gpw_v4_population_density_rev11_2005_1_deg.asc (431 KB) gpw_v4_population_density_rev11_2005_1_deg.asc Ascii file

Replies (2)

RE: How to convert gridded population Ascii file to Netcdf file - Added by Karin Meier-Fleischer over 2 years ago

Hi Shoaib,

the input file contains 6 header lines which have to be deleted.
Furthermore the gridfile is wrong, the xstart and ystart values are wrong (see header of input file) and the yinc has to be negative.
And last but not least the data contains missing values (see header of input file again).

1. Delete header lines at the top of the input file.

2. Modify the gridfile.txt

gridtype  = lonlat
gridsize  = 64800
xsize     = 360
ysize     = 180
xname     = lon
xlongname = longitude
xunits    = degrees_east
xfirst    = -180.0
xinc      = 1.0
yname     = lat
ylongname = latitude
yunits    = degrees_north
yname     = lat
yfirst    = 90.0
yinc      = -1.0

3. The CDO command has to be

cdo -f nc -settaxis,2005-01-01,00:00:00,1day -setctomiss,-9999 -setname,population -input,gridfile.txt population1_with_missing_values.nc < gpw_v4_population_density_rev11_2005_1_deg.asc

-Karin

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