ABOUT_DRIFTERS is the jdata module of jLab.

 ABOUT_DRIFTERS  Global surface drifter dataset from the Global Drifter Program. 
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    DRIFTERS.MAT and DRIFTERS.NC contain the global surface drifter dataset 
    from NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML)
    Global Drifter Program (GDP) Drifter Data Assembly Center, online at
 
        http://www.aoml.noaa.gov/phod/dac/index.php
 
    This data differs from AOML's version in that all gaps up to two days 
    have been filled with linear interpolation, trajectory segments have 
    been split at any gaps longer than two days, and only drifter records 
    with at least one week of data are returned.  
 
    DRIFTERS.MAT is a Matlab version, and DRIFTERS.NC is a NetCDF version.
 
    DRIFTERS is distributed as a part of JDATA, a supplement to the 
    software toolbox JLAB, and is available at http://www.jmlilly.net.
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    Matlab version
 
    LOAD DRIFTERS loads the structure DRIFTERS, with the following fields:
 
        drifters.about     Pointer to this document            
        drifters.id        Drifter ids                 [22058 x 1 array] 
        drifters.buoy      Drifter buoy type           [22058 x 1 array] 
        drifters.num       Date in DATENUM format      {22058 x 1 cell} 
        drifters.lat       Latitudes                   {22058 x 1 cell} 
        drifters.lon       Longitudes                  {22058 x 1 cell} 
        drifters.u         Eastward velocity in cm/s   {22058 x 1 cell}   
        drifters.v         Northward velocity in cm/s  {22058 x 1 cell}   
        drifters.t         Temperature in centigrade   {22058 x 1 cell} 
        drifters.flag      Drogue presence flag        {22058 x 1 cell}   
        drifters.filled    True if data was filled     {22058 x 1 cell}   
 
    NUM, LAT, LON, U, V, T, and FLAG are all cell arrays, with one drifter 
    per cell.
 
    BUOY, FLAG and FILLED are metadata information described below.
 
    A number of routines are available in JLAB to work directly with such
    cell arrays, see JCELL.  In particular, CELLPLOT will plot such data.
 
    After 'load drifters', type 'use drifters' to map the structure fields 
    into named variables in the workspace--id, num, lat, lon, etc.
 
    To plot the entire drifter dataset, as in the above figure, type 
 
       load drifters, use drifters, cellplot(380,lon,lat), topoplot
 
    where 380 specifies the right-hand axis of the plot, chosen to be 
    the longitude of the southern tip of Africa.
 
    To convert the cell arrays into one long column vector, with a NAN 
    separating each drifter, type 'cell2col(num,lat,lon,u,v,t);'.
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    Metadata
 
    The fields BUOY and FLAG give metadata information. BUOY is the drifter
    design type according to the following code:
 
       1=SVP,  2=SVPB, 3=SVPC, 4=SVPBS, 5=SVPW, 6=SVPBW.
 
    FLAG is true when the drifter's drogue is estimated to be present, and
    false otherwise. 
 
    FILLED is true for data points that have been filled with linear 
    interpolation.  This is done for all gaps up to two days.
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    NetCDF version
  
    The NetCDF version is basically the same as the mat-file version, but
    having all the cell array fields stored as column arrays with 
    separating NaNs, see COL2CELL.
 
    Use the JLAB routine NCLOAD to load the NetCDF file and convert all the
    NaN-separated columns into cells, i.e. 'ncload drifters'.
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    Dataset creation
 
    The files on which DRIFTERS is based are available for download at 
 
        http://www.aoml.noaa.gov/envids/gld/FtpInterpolatedInstructions.php
 
    For completeness, the m-file ABOUT_DRIFTERS also contains the 
    processing steps used in the creation of DRIFTERS.MAT and DRIFTERS.NC.  
 
    If you wish to do this yourself, with JLAB on your search path, 
    'about_drifters --create' will recreate DRIFTERS.MAT and DRIFTERS.NC
    by reading in the original downloaded data.  This will take a while.
 
    As of January 2019, the AOML drifter dataset consists of eight files:
    
            buoydata_1_5000.dat
            buoydata_5001_10000.dat
            buoydata_10001_15000.dat
            buoydata_15001_jun18.dat
            dirfl_1_5000.dat
            dirfl_5001_10000.dat
            dirfl_10001_15000.dat
            dirfl_15001_jun18.dat
 
    You'll need to make sure to put the directory containing the files on
    your Matlab search path using ADDPATH, e.g. 'addpath ~/Data/aoml'.
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    See also JDATA, ABOUT_FLOATS.
 
    'about_drifters --f' generates the sample figure shown above.
 
    Usage: about_drifters
           about_drifters --create     
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2007--2019 J.M. Lilly --- type 'help jlab_license' for details

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