I'm trying to write a test for code that works with hycom netcdf global ocean circulation data. The source file 2 subdatasets:
gdalinfo hycom_glb_911_2015110200_t000_uv3z.nc | grep _NAME
SUBDATASET_1_NAME=NETCDF:"hycom_glb_911_2015110200_t000_uv3z.nc":water_u
SUBDATASET_2_NAME=NETCDF:"hycom_glb_911_2015110200_t000_uv3z.nc":water_v
With 40 depth bands:
gdalinfo NETCDF:hycom_glb_911_2015110200_t000_uv3z.nc:water_u | grep '^Band' | head -3
Band 1 Block=4500x1 Type=Int16, ColorInterp=Undefined
Band 2 Block=4500x1 Type=Int16, ColorInterp=Undefined
Band 3 Block=4500x1 Type=Int16, ColorInterp=Undefined
I've got some code written the does things like calculate the speed in m/s from the UV and creates a geotiff, etc. The original files are much too large for using in unittests. Is there an easy way with gdal, nco or ? to keep the structure and metadata, but create a much smaller file? I'm open to dropping all but the first two bands and writing a constant value into each band + turning on deflate compression.
Trying with GDAL:
gdal_translate --version # At head -> r31584
GDAL 2.1.0dev, released 2015/99/99
gdal_translate hycom_glb_911_2015110200_t000_uv3z.nc hycom_glb_911_2015110200_t000_uv3z-try2.nc -of netcdf -co compress=deflate
Input file contains subdatasets. Please, select one of them for reading.
The originals are quite a bit large for tests:
wget ftp://ftp.hycom.org/datasets/GLBu0.08/expt_91.1/data/hindcasts/2015/hycom_glb_911_2015110200_t000_uv3z.nc
ls -lh hycom_glb_911_2015110200_t000_uv3z.nc
-rw-r----- 1 schwehr group 1.4G Nov 19 09:13 hycom_glb_911_2015110200_t000_uv3z.nc
The details of the source netcdf file:
ncdump -h hycom_glb_911_2015110200_t000_uv3z.nc
netcdf hycom_glb_911_2015110200_t000_uv3z {
dimensions:
lat = 2001 ;
lon = 4500 ;
depth = 40 ;
time = UNLIMITED ; // (1 currently)
variables:
double time(time) ;
time:long_name = "Valid Time" ;
time:units = "hours since 2000-01-01 00:00:00" ;
time:time_origin = "2000-01-01 00:00:00" ;
time:calendar = "gregorian" ;
time:axis = "T" ;
time:NAVO_code = 13 ;
double tau(time) ;
tau:long_name = "Tau" ;
tau:units = "hours since analysis" ;
tau:time_origin = "2015-11-02 00:00:00" ;
tau:NAVO_code = 56 ;
double depth(depth) ;
depth:long_name = "Depth" ;
depth:standard_name = "depth" ;
depth:units = "m" ;
depth:positive = "down" ;
depth:axis = "Z" ;
depth:NAVO_code = 5 ;
double lat(lat) ;
lat:long_name = "Latitude" ;
lat:standard_name = "latitude" ;
lat:units = "degrees_north" ;
lat:point_spacing = "even" ;
lat:axis = "Y" ;
lat:NAVO_code = 1 ;
double lon(lon) ;
lon:long_name = "Longitude" ;
lon:standard_name = "longitude" ;
lon:units = "degrees_east" ;
lon:modulo = "360 degrees" ;
lon:axis = "X" ;
lon:NAVO_code = 2 ;
short water_u(time, depth, lat, lon) ;
water_u:long_name = "Eastward Water Velocity" ;
water_u:standard_name = "eastward_sea_water_velocity" ;
water_u:units = "m/s" ;
water_u:_FillValue = -30000s ;
water_u:missing_value = -30000s ;
water_u:scale_factor = 0.001f ;
water_u:add_offset = 0.f ;
water_u:NAVO_code = 17 ;
short water_v(time, depth, lat, lon) ;
water_v:long_name = "Northward Water Velocity" ;
water_v:standard_name = "northward_sea_water_velocity" ;
water_v:units = "m/s" ;
water_v:_FillValue = -30000s ;
water_v:missing_value = -30000s ;
water_v:scale_factor = 0.001f ;
water_v:add_offset = 0.f ;
water_v:NAVO_code = 18 ;
// global attributes:
:classification_level = "UNCLASSIFIED" ;
:distribution_statement = "Approved for public release. Distribution unlimited." ;
:downgrade_date = "not applicable" ;
:classification_authority = "not applicable" ;
:institution = "Naval Oceanographic Office" ;
:source = "HYCOM archive file" ;
:history = "archv2ncdf3z" ;
:field_type = "instantaneous" ;
:Conventions = "CF-1.0 NAVO_netcdf_v1.0" ;
