ABOUT_JTOPO is the jOceans module of jLab.

 ABOUT_JTOPO  One-sixth degree global topography, from Smith and Sandwell + IBCAO.
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    JTOPO is a matfile containing smoothed one-sixth degree global 
    topography based on the Smith and Sandwell database version together 
    with the International Bathymetric Chart of the Arctic Ocean (IBCAO).
 
    LOAD JTOPO loads the structure JTOPO, with the following fields:
 
        jtopo.about     Pointer to this document  
        jtopo.lat       Array of latitudes         [1024 x 1] 
        jtopo.lon       Array of longitudes        [1 x 2160]
        jtopo.topo      Matrix of topography       [1024 x 2160]
 
    Typing 'use jtopo' maps these fields into variables in the current
    workspace, e.g. 'use jtopo, pcolor(lon,lat,topo), shading interp'.
 
    TOPO is in units of kilometers and is positive for above sea level, 
    and negative for below sea level.  
 
    LAT is uniformly spaced from -80.666 to  89.833, and LON is uniformly
    spaced from -180 to 179.8333.  These are *grid-centered* values, that 
    is, they indicate midpoints of the topography cells.
 
    JTOPO is distributed with JLAB, available at http://www.jmlilly.net.
 
    See also READTOPO, which reads in any region of the Smith and Sandwell 
    data, ABOUT_IBCAO, and TOPOPLOT, which makes simple plots using JTOPO.
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    Processing
 
    The one-minute Smith and Sandwell data, and 1/2 minute IBCAO data, are
    smoothed to one-sixth of a degree by averaging in 1/6 x 1/6 bins. 
 
    Smith and Sandwell is defined from -80.738 and 80.738, while IBCAO is 
    defined from 64 N to 90 N.  In the overlap region, from 64 to 84.738 N,
    the root-mean-square different between the two datasets is about 50 m.
 
    JTOPO uses a linear blend to resolve the small discrepencies in the 
    overlap region.  From 64 to 84.738 N, JTOPO transitions from being all
    Smith and Sandwell, to all IBCAO, with a weighted average in between.
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    Data and documentation
 
    This dataset is based on the Smith and Sandwell Global Topography 
    Dataset v. 18.1 and IBCAO v. 3.0, which are included with JDATA.
 
    The source and reference for the Smith and Sandwell dataset are
 
        http://topex.ucsd.edu/WWW_html/mar_topo.html
 
       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.
 
    The source and reference for the IBCAO dataset are
 
       http://www.ngdc.noaa.gov/mgg/bathymetry/arctic/grids/version3_0/
 
       Jakobsson, M., L. A. Mayer, B. Coakley, J. A. Dowdeswell, S. Forbes,
           B. Fridman, H. Hodnesdal, R. Noormets, R. Pedersen, M. Rebesco,
           H.-W. Schenke, Y. Zarayskaya A, D. Accettella, A. Armstrong, 
           R. M. Anderson, P. Bienhoff, A. Camerlenghi, I. Church, 
           M. Edwards, J. V. Gardner, J. K. Hall, B. Hell, O. B. Hestvik, 
           Y. Kristoffersen, C. Marcussen, R. Mohammad, D. Mosher, 
           S. V. Nghiem, M. T. Pedrosa, P. G. Travaglini, and 
           P. Weatherall, The International Bathymetric Chart of the Arctic
           Ocean (IBCAO) Version 3.0, Geophysical Research Letters, 
           doi: 10.1029/2012GL052219
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    License and Copyright 
 
    JTOPO.MAT 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, see TOPO_COPYRIGHT.
 
    No copyright or policy is specified in the IBCAO documentation. 
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    Dataset creation
 
    For completeness, the m-file ABOUT_JTOPO also contains the processing 
    steps used in the creation of JTOPO.MAT.  
 
    If you wish to do this yourself, with JLAB on your search path, 
    'about_jtopo --create' will recreate the JTOPO.MAT dataset by reading  
    in and averaging the two topographic datasets. This will take a while.
 
    For this to work you will need to have the JDATA folder containing
    file 'topo_18.1.img' and 'ibcao.mat' downloaded and on your Matlab 
    search path. 
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    See also READTOPO, TOPOPLOT, JDATA.
 
    'about_jtopo --f' generates the sample figure shown above.
 
    Usage: about_jtopo
           about_jtopo --create
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2014--2015 J.M. Lilly --- type 'help jlab_license' for details

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