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 is a matfile containing 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
 
    All gaps have been filled with linear interpolation, and only drifter
    records with at least one week of data are returned.  
 
    The current version of DRIFTERS.MAT contains data through Sept. 2016, 
    with all the data updated since AOML's major revision in March 2016.
 
    LOAD DRIFTERS loads the structure DRIFTERS, with the following fields:
 
        drifters.about     Pointer to this document            
        drifters.id        Drifter ids                 [20577 x 1 array] 
        drifters.buoy      Drifter buoy type           [20577 x 1 array] 
        drifters.num       Date in DATENUM format      {20577 x 1 cell} 
        drifters.lat       Latitudes                   {20577 x 1 cell} 
        drifters.lon       Longitudes                  {20577 x 1 cell} 
        drifters.t         Temperature in centigrade   {20577 x 1 cell} 
        drifters.cv        Velocity u+iv in cm/s       {20577 x 1 cell}   
        drifters.cvo       AOML velocity u+iv in cm/s  {20577 x 1 cell}   
        drifters.flag      Drogue presence flag        {20577 x 1 cell}   
 
    NUM, LAT, LON, T, CV, and FLAG are all cell arrays, with one drifter 
    per cell.
 
    BUOY and FLAG are metadata information described in more detail below.
 
    The two velocity fields CV and CVO differ in their computation.  CVO
    is the original velocity product distributed by AOML, whereas CV is 
    computed from the 6-hourly positions using LATLON2UV.
 
    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,t,cv);'.
 
    DRIFTERS.MAT 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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    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. 
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    Dataset creation
 
    The ASCII files on which DRIFTERS.MAT is based are available for 
    download from AOML 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 DRIFTER.MAT.  
 
    If you wish to do this yourself, with JLAB on your search path, 
    'about_drifters --create' will recreate DRIFTERS.MAT by reading in the
    original data as downloaded from AOML.  This will take a while.
 
    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'.
 
    As of March 2017, the AOML drifter dataset consists of three files:
    
            buoydata_1_5000.dat
            buoydata_5001_10000.dat
            buoydata_10001_sep16.dat
 
    These should placed in the directory specified above in order for 
    ABOUT_DRIFTERS.M to create DRIFTERS.MAT.
 
    Note that the velocity CV in DRIFTERS.MAT is computed from latitude,
    longitude, and time using LATLON2UV.  It is not quite the same as the
    velocity field produced by 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--2017 J.M. Lilly --- type 'help jlab_license' for details    

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