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[Staging #FJY-535537]: Blended SST retrieve - Doubt



Hi Ricardo,

re:
> This is the website I am trying to retrieve the data:
> 
> http://ourocean.jpl.nasa.gov:8080/thredds/dodsC/g1sst/sst_20100725.nc.html

OK, thanks.

There are two ways to do what you want:

- install OPeNDAP client software that will allow you to programmatically 
  request the data.  I just used the Unidata IDV to access the data off
  of the OPeNDAP server you provided and was able to plot the SST values
  and save the values plotted to a disk file.

- specify the subset of the data manually through the web page you reference
  above.

  This approach will be more difficult since the control for selecting a 
subdomain
  for the data is in index space, not LatxLon space.  The good news, however, is
  that the mapping from index space to LatxLon space appears straightforward:

             Index        Degrees
  Longitude: 0..35999     -180..180
  Latitude:  0..15999     -80..80

  So, there are 100 points per degree in both Latitude and Longitude.

- you can download this data as a netcdf file using ncdump from the current
  netcdf release (4.1.2)

  The following command would show how this file will look when accessed thru 
ncdump:

  ncdump -h ncdump ncdump 
"http://ourocean.jpl.nasa.gov:8080/thredds/dodsC/g1sst/sst_20100725.nc";

  This should produce the following output:

netcdf sst_20100725 {
dimensions:
        time = UNLIMITED ; // (1 currently)
        lat = 16000 ;
        lon = 36000 ;
variables:
        float time(time) ;
                time:unit = "hours since 1981-01-01 00:00:00" ;
        float lon(lon) ;
                lon:long_name = "longitude" ;
                lon:standard_name = "longitude" ;
                lon:axis = "X" ;
                lon:units = "degrees_east" ;
        float lat(lat) ;
                lat:long_name = "latitude" ;
                lat:standard_name = "latitude" ;
                lat:axis = "Y" ;
                lat:units = "degrees_north" ;
        short SST(time, lat, lon) ;
                SST:missingValue = -32768 ;
                SST:add_offset = 273.15 ;
                SST:scale_factor = 0.01 ;
                SST:_FillValue = -32768s ;
        byte data_days(lat, lon) ;
                data_days:missingValue = -99s ;
                data_days:_FillValue = -99b ;

// global attributes:
                :history = "Sun Sep 21 20:25:02 2008: ncatted -a 
fillValue,SST,d,, global_1km_02_short.nc\n",
                        "Sun Sep 21 20:16:06 2008: ncatted -a 
_FillValue,SST,c,s,-32768 global_1km_02_short.nc" ;
}

  We can access, say the variable SST within the specified bounding box by
  defining a constraint expression:
      ?SST[0:0][4000:8000][13000:15000]
  Remember that the dimensions are zero-based, so if the arithmetic is correct
  the lat range [-40,0] should correspond to the index range [4000,8000]
  and the lon range [-50,-30] should correspond to the index range 
[13000:15000].

  This subset of data can then be downloaded using ncdump using this command:
    ncdump 
"http://ourocean.jpl.nasa.gov:8080/thredds/dodsC/g1sst/sst_20100725.nc?SST[0:0][4000:8000][13000:15000]

As you can see, there are several options for getting the data.  The most useful
of these would probably be to adopt the use of an application that supports
direct, programmatic access to data hosted on OPeNDAP servers.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: FJY-535537
Department: Support THREDDS
Priority: Normal
Status: Closed


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