Thanks! That gets it down to 268K! ncks -4 --deflate 9 -v water_u,water_v -d depth,1,2,1 -d lon,0,360,10 hycom_glb_911_2015110200_t000_uv3z.nc out4.nc
On Thu, Nov 19, 2015 at 12:22 PM, Julien Demaria <julien.dema...@acri-st.fr> wrote: > If you want to reduce again your file you should be able to keep 0..360 > but change the step by decimating: -d lon,0,360,10 for example to keep only > 37 longitudes. > http://research.jisao.washington.edu/data_sets/nco/#example10 > > Julien > > ------------------------------ > *De :* Kurt Schwehr [schw...@gmail.com] > *Date d'envoi :* jeudi 19 novembre 2015 21:10 > *À :* Julien Demaria > *Cc :* gdal dev > *Objet :* Re: RE : [gdal-dev] Making a small(er) test netcdf from a > netcdf with subdatasets? > > Julien, > > Bummer that I broke you patches. I don't expect to do much more in frmts > for a while. My big sprint is done and I will likely only do a couple > hours each Friday. My focus will likely be finishing ports/ and working on > gcore and then ogr. > > Here is what I currently have based on comments from gis stack exchange. > In my case, I sadly can't use your lon/lat bounds shrinking as need to test > my code that shifts the data from 0..360 to -180..180. > > ncks -4 --deflate 9 -v water_u,water_v -d depth,1,2,1 > hycom_glb_911_2015110200_t000_uv3z.nc out.nc > > That takes 1.4GB down to 33MB. > > -kurt > > On Thu, Nov 19, 2015 at 11:56 AM, Julien Demaria < > julien.dema...@acri-st.fr> wrote: > >> Dear Kurt, >> >> Yes you can do that using ncks from nco by specifying the subset on each >> dimension: >> ncks -d lon,340.0,10.0 -d lat,10.0,20.0 in.nc out.nc >> another solution is to do ncdump -h into a file, editing the ascii to >> reduce dimensions and do ncgen to generate the NetCDF. By default it will >> fill with fillvalue, but you can also add data at the end in the ascii file. >> >> Using gdal I think it is impossible to keep the exact input structure but >> I'm not sure 100%. >> >> By the way, do you plan to do other improvements/big >> refactorings/cleanings in short term on the NetCDF driver? I still plan to >> finalize this >> http://lists.osgeo.org/pipermail/gdal-dev/2015-February/040973.html >> I have to add unit tests to finalize this, but I have seen that your >> recent commits completely break my patches, but this is my fault because I >> should have done before, but time is missing... :-( >> >> Cheers, >> Julien >> >> ------------------------------ >> *De :* gdal-dev [gdal-dev-boun...@lists.osgeo.org] de la part de Kurt >> Schwehr [schw...@gmail.com] >> *Date d'envoi :* jeudi 19 novembre 2015 20:22 >> *À :* gdal dev >> *Objet :* [gdal-dev] Making a small(er) test netcdf from a netcdf with >> subdatasets? >> >> Also asked here: >> http://gis.stackexchange.com/questions/170882/how-can-a-make-a-netcdf-with-subgroups-smaller >> >> Is there an easy way to make a netcdf with subdatasets but shrink it >> without resorting to C or Fortan? >> >> 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: >> >> 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 >> >> Thanks, >> -kurt >> > > > > -- > -- > http://schwehr.org > -- -- http://schwehr.org
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