ABOUT_SANDWELL is the jdata module of jLab.

 ABOUT_SANDWELL  One minute resolution topography data from Smith and Sandwell. 
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    SANDWELL.MAT and SANDWELL.NC contain nearly-global topography data from 
    the Smith and Sandwell database version 18.1, at its full, 
    approximately one minute resolution.
 
    SANDWELL.MAT is a Matlab version, while SANDWELL.NC is a NetCDF 
    version. These both contain identical data.
 
    SANDWELL is distributed as a part of JDATA, a supplement to the 
    software toolbox JLAB, and is available at http://www.jmlilly.net.
 
    In Matlab, LOAD SANDWELL for the Matlab version, or NCLOAD SANDWELL for 
    the NetCdf version, leads to a structure containing the following fields
 
        sandwell.about     Pointer to this document  
        sandwell.lat       Array of latitudes         [17280 x 1] 
        sandwell.lon       Array of longitudes        [21600 x 1]
        sandwell.topo      Matrix of topography       [17280 x 21600]
 
    Typing 'use sandwell' maps these fields into variables in the current
    workspace.
 
    TOPO is a matrix of topography in units of kilometers and is positive 
    for above sea level, and negative for below sea level. 
 
    LAT and LON output are *grid-centered*, that is, they indicate 
    midpoints of the topography cells. LON is uniformly spaced, but LAT is 
    non-uniformly spaced, with bin sizes decreasing poleward.
 
    Note that the Smith and Sandwell database is defined only for latitudes
    between -80.738 and 80.738.  Topography at higher northern latitudes is
    found in the IBCAO dataset, see ABOUT_IBCAO.
 
    JTOPO.MAT, a 1/6th degree version of SANDWELL merged with high-latitude
    data from the International Bathymetric Chart of the Arctic Ocean 
    (IBCAO), is distributed with JLAB; see ABOUT_JTOPO for details.
 
    Forming regional datasets is more convenient by directly accessing the 
    original binary file, topo_18.1.img.  This can be read using READTOPO.
    READTOPO and topo_18.1.img are distributed together with SANDWELL.
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    Data and documentation
 
    The original location for the Smith and Sandwell Global Topography
    Dataset v. 18.1, file 'topo_18.1.img' is
 
        http://topex.ucsd.edu/WWW_html/mar_topo.html.
 
    The reference for the Smith and Sandwell Database is
 
       Smith, W. H. F., and D. T. Sandwell, Global seafloor topography 
       from satellite altimetry and ship TOPO soundings, Science, v. 277, 
       p. 1957-1962, 26 Sept., 1997.
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    License and Copyright 
 
    The data file topo_18.1.img is distributed with JDATA for RESEARCH AND 
    NON-PROFIT USE ONLY, in accordance with the copyright statement for the
    Smith and Sandwell dataset.  For details, type 'help topo_copyright'.
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    Dataset creation
 
    For completeness, the m-file ABOUT_SANDWELL also contains steps used in 
    the creation of SANDWELL.MAT and SANDWELL.NC. If you wish to do this 
    yourself, typing 'about_sandwell --create' with JLAB installed and with 
    topo_18.1.img on your search path will recreate SANDWELL. 
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    See also ABOUT_IBCAO, and JTOPO, REGIONPLOT, and TOPOPLOT in JLAB.
 
    'about_sandwell --f' generates the sample figure shown above.
 
    Usage: about_sandwell
           about_sandwell --create
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2015--2019 J.M. Lilly --- type 'help jlab_license' for details

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