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  The program uses files from the Globally Self-consistent Hierarchical High-resolution Shoreline
  (GSHHS) data base to draw shorelines in the manner of MAP_CONTINENTS. In other words,
  it is assumed that a map coordinate data space has been established prior to calling
  this routine. See the example below. The GSHHS data files are
  `available for downloading <http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html>`.
  An `article describing how to use this program <http://www.idlcoyote.com/map_tips/gshhs.html>`
  is also available.
  Note, the authors of the GSHHS software *continually* change the header
  structure, which you MUST know to read the data file. There are are now
  at least four different structures in common use. Please find the one
  you need from the commented list in the code itself. The current code uses the structure
  for the 2.2 version of the GSHHS software.


    Graphics, Map Projections


    filename: in, optional, type=string
      The name of the GSHHS file to open. If not provided, the user will
      be asked to select the file with a file selection tool.


    addcmd: in, optional, type=boolean, default=0
        If this keyword is set, the object is added to the resizeable graphics
        window, cgWindow. Note that a map projection command must be
        added to the window before this command is added to be effective.
    color: in, optional, type=string, default="opposite"
        The name of the drawing color.
    fill: in, optional, type=boolean, default=0
        Set this keyword to draw filled outlines.
    land_color: in, optional, type=string, default="tan8"
        The name of the land color (for FILL).
    level: in, optional, type=integer, default=2
        The polygon LEVEL. All polygons less than or equal to this value
        are drawn. 1-land, 2-lakes, 3-island in lake, 4-pond in island.
        By default, 2 (land and lake outlines).
    map_structure: in, optional, type=varies
        A map projection structure (as created from MAP_PROJ_INIT) or a map coordinate
        object (i.e., cgMap). If using a map projection structure, a map coordinate system
        must be set up for the entire display window.
    minarea: in, optional, type=float, default=500
        The minimum feature area in square kilometers. Features with area below
        the minimum area will not be drawn on the map.
    noclip: in, optional, type=boolean, default=0
        Normally the polygons and outlines are clipped to the plot boundaries.
        Set this keyword to turn this feature off.
    outline: in, optional, type=boolean
        Set this keyword to draw outlines on filled polygons. Set to 1, by default,
        if FILL=0. Set to zero to not draw outlines on filled polygons.
    thick: in, optional, type=integer, default=!P.Thick
        Set this keyword to the thickness of the lines that are drawn.
    water_color: in, optional, type=string, default="sky blue"
        The name of color to draw water features in.


    David W. Fanning
    1645 Sheely Drive
    Fort Collins, CO 80526 USA
    Phone: 970-221-0438 <
    E-mail: david@idlcoyote.com
    Coyote's Guide to IDL Programming: http://www.idlcoyote.com


    Example using cgMAP_SET to set up the map coordinate space::
        datafile = 'gshhs_h.b'
        cgDisplay, 500, 350
        pos = [0.1,0.1, 0.9, 0.8]
        cgMap_Set, -25.0, 135.0, Position=pos, /Mercator, Scale=64e6, Color='black'
        cgColorfill, [pos[0], pos[0], pos[2], pos[2], pos[0]], $
                      [pos[1], pos[3], pos[3], pos[1], pos[1]], $
                      /Normal, Color='sky blue'
        cgMap_GSHHS, datafile, Fill=1, Level=3, Color='black', /Outline
        cgText, 0.5, 0.85, 'Australia', Font=0, Color='black', /Normal, Alignment=0.5
        cgPlotS, [pos[0], pos[0], pos[2], pos[2], pos[0]], $
                  [pos[1], pos[3], pos[3], pos[1], pos[1]], $
                  /Normal, Color='black', Thick=2
    Example using MAP_PROJ_INIT to set up the map coordinate space::
        datafile = 'gshhs_h.b'
        map = Obj_New('cgMap', "Lambert Azimuthal", Limit=[40, -95, 50, -75], $
            Center_Lat=45, Center_Lon=-85)
        map -> SetProperty, Position=[0.1, 0.1, 0.90, 0.75], /Draw
        cgMap_GSHHS, datafile, /Fill, Level=3, Map_Structure=map, $
            Water='DODGER BLUE'
        cgMap_Grid, /Label, /Box, Color='charcoal', Map_Structure=map
        cgMap_Continents, /USA, Map_Structure=map
        cgText, 0.5, 0.85, 'Great Lakes Region', Font=0, Color='charcoal', $
            /Normal, Alignment=0.5


Modification History

        Written by David W. Fanning, from Map_GSHHS_Shoreline program, 12 November 2011.
        Added THICK keyword. 28 Dec 2011. DWF.
        Modified so you can pass a map object with the MAP_STRUCTURE keyword and not
          have it change the object to a structure. 5 April 2012. DWF.


    Copyright (c) 2011, Fanning Software Consulting, Inc.

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