ABOUT_SANDWELL is the jdata module of jLab.

 ABOUT_SANDWELL  One minute resolution topography data from Smith and Sandwell. 
    SANDWELL.MAT is a matfile containing nearly-global topography data from 
    the Smith and Sandwell database version 18.1, at its full, 
    approximately one minute resolution.
    LOAD SANDWELL loads the structure SANDWELL, with the following fields:
        sandwell.about     Pointer to this document  
        sandwell.lat       Array of latitudes         [17280 x 1] 
        sandwell.lon       Array of longitudes        [1 x 21600]
        sandwell.topo      Matrix of topography       [17280 x 21600]
    Typing 'use sandwell' maps these fields into variables in the current
    TOPO is a matrix of topography in units of kilometers and is positive 
    for above sea level, and negative for below sea level.  LON is a row
    vector of longitudes and LAT a column vector of latitudes.
    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.
    SANDWELL.MAT is distributed with JLAB at http://www.jmlilly.net.
    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.MAT.
    Data and documentation
    The original location for the Smith and Sandwell Global Topography
    Dataset v. 18.1, file 'topo_18.1.img' is
    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.
    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'.
    Dataset creation
    For completeness, the m-file ABOUT_SANDWELL also contains steps used in 
    the creation of SANDWELL.MAT. If you wish to do this yourself, typing
    'about_sandwell --create' with JLAB installed will recreate 
    SANDWELL.MAT from source. 
    'about_sandwell --f' generates the sample figure shown above.
    Usage: about_sandwell
           about_sandwell --create
    This is part of JLAB --- type 'help jlab' for more information
    (C) 2015 J.M. Lilly --- type 'help jlab_license' for details

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