<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style id="owaParaStyle" type="text/css">P {margin-top:0;margin-bottom:0;}</style>
</head>
<body ocsi="0" fpstyle="1">
<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">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.<br>
<a href="http://research.jisao.washington.edu/data_sets/nco/#example10" target="_blank">http://research.jisao.washington.edu/data_sets/nco/#example10</a><br>
<br>
Julien<br>
<br>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">
<hr tabindex="-1">
<div style="direction: ltr;" id="divRpF280794"><font color="#000000" size="2" face="Tahoma"><b>De :</b> Kurt Schwehr [schwehr@gmail.com]<br>
<b>Date d'envoi :</b> jeudi 19 novembre 2015 21:10<br>
<b>À :</b> Julien Demaria<br>
<b>Cc :</b> gdal dev<br>
<b>Objet :</b> Re: RE : [gdal-dev] Making a small(er) test netcdf from a netcdf with subdatasets?<br>
</font><br>
</div>
<div></div>
<div>
<div dir="ltr">Julien,
<div><br>
</div>
<div>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. </div>
<div><br>
</div>
<div>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. <br>
<div><br>
</div>
<div>ncks -4 --deflate 9 -v water_u,water_v -d depth,1,2,1 <a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">
hycom_glb_911_2015110200_t000_uv3z.nc</a> <a href="http://out.nc" target="_blank">
out.nc</a><br>
</div>
</div>
<div><br>
</div>
<div>That takes 1.4GB down to 33MB.</div>
<div><br>
</div>
<div>-kurt</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, Nov 19, 2015 at 11:56 AM, Julien Demaria <span dir="ltr">
<<a href="mailto:Julien.Demaria@acri-st.fr" target="_blank">Julien.Demaria@acri-st.fr</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
<div>
<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Dear Kurt,<br>
<br>
Yes you can do that using ncks from nco by specifying the subset on each dimension:<br>
<font size="+1"><code>ncks -d lon,340.0,10.0 -d lat,10.0,20.0 <a href="http://in.nc" target="_blank">
in.nc</a> <a href="http://out.nc" target="_blank">out.nc</a></code></font><br>
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.<br>
<br>
Using gdal I think it is impossible to keep the exact input structure but I'm not sure 100%.<br>
<br>
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<br>
<a href="http://lists.osgeo.org/pipermail/gdal-dev/2015-February/040973.html" target="_blank">http://lists.osgeo.org/pipermail/gdal-dev/2015-February/040973.html</a><br>
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... :-(<br>
<br>
Cheers,<br>
Julien<br>
<br>
<div style="font-family:Times New Roman; color:#000000; font-size:16px">
<hr>
<div style="direction:ltr"><font color="#000000" size="2" face="Tahoma"><b>De :</b> gdal-dev [<a href="mailto:gdal-dev-bounces@lists.osgeo.org" target="_blank">gdal-dev-bounces@lists.osgeo.org</a>] de la part de Kurt Schwehr [<a href="mailto:schwehr@gmail.com" target="_blank">schwehr@gmail.com</a>]<br>
<b>Date d'envoi :</b> jeudi 19 novembre 2015 20:22<br>
<b>À :</b> gdal dev<br>
<b>Objet :</b> [gdal-dev] Making a small(er) test netcdf from a netcdf with subdatasets?<br>
</font><br>
</div>
<div>
<div class="h5">
<div></div>
<div>
<div dir="ltr">Also asked here: <a href="http://gis.stackexchange.com/questions/170882/how-can-a-make-a-netcdf-with-subgroups-smaller" target="_blank">
http://gis.stackexchange.com/questions/170882/how-can-a-make-a-netcdf-with-subgroups-smaller</a><br>
<div><br>
</div>
<div>Is there an easy way to make a netcdf with subdatasets but shrink it without resorting to C or Fortan?</div>
<div><br>
</div>
<div>
<div>I'm trying to write a test for code that works with hycom netcdf global ocean circulation data. The source file 2 subdatasets:</div>
<div><br>
</div>
<div>gdalinfo <a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">
hycom_glb_911_2015110200_t000_uv3z.nc</a> | grep _NAME</div>
<div> SUBDATASET_1_NAME=NETCDF:"<a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">hycom_glb_911_2015110200_t000_uv3z.nc</a>":water_u</div>
<div> SUBDATASET_2_NAME=NETCDF:"<a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">hycom_glb_911_2015110200_t000_uv3z.nc</a>":water_v</div>
<div>With 40 depth bands:</div>
<div><br>
</div>
<div>gdalinfo NETCDF:hycom_glb_911_<a href="tel:2015110200" value="+12015110200" target="_blank">2015110200</a>_t000_uv3z.nc:water_u | grep '^Band' | head -3</div>
<div>Band 1 Block=4500x1 Type=Int16, ColorInterp=Undefined</div>
<div>Band 2 Block=4500x1 Type=Int16, ColorInterp=Undefined</div>
<div>Band 3 Block=4500x1 Type=Int16, ColorInterp=Undefined</div>
<div>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.</div>
<div><br>
</div>
<div>Trying with GDAL:</div>
<div><br>
</div>
<div>gdal_translate --version # At head -> r31584</div>
<div>GDAL 2.1.0dev, released 2015/99/99</div>
<div><br>
</div>
<div>gdal_translate <a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">
hycom_glb_911_2015110200_t000_uv3z.nc</a> <a href="http://hycom_glb_911_2015110200_t000_uv3z-try2.nc" target="_blank">
hycom_glb_911_2015110200_t000_uv3z-try2.nc</a> -of netcdf -co compress=deflate</div>
<div>Input file contains subdatasets. Please, select one of them for reading.</div>
<div>The originals are quite a bit large for tests:</div>
<div><br>
</div>
<div>ls -lh <a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">
hycom_glb_911_2015110200_t000_uv3z.nc</a></div>
<div>-rw-r----- 1 schwehr group 1.4G Nov 19 09:13 <a href="http://hycom_glb_911_2015110200_t000_uv3z.nc" target="_blank">
hycom_glb_911_2015110200_t000_uv3z.nc</a></div>
</div>
<div><br>
</div>
<div>Thanks,</div>
<div>-kurt</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<div><br>
</div>
-- <br>
<div class="gmail_signature">--
<div><a href="http://schwehr.org" target="_blank">http://schwehr.org</a></div>
</div>
</div>
</div>
</div>
</div>
</body>
</html>