CGMAP_GSHHS

CGMAP_GSHHS
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.

Params

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.

Keywords

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.

Author

FANNING SOFTWARE CONSULTING::
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

Examples

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'
cgDisplay
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

History

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.