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
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