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EQPOLE_GRID

EQPOLE_GRID

Name


      EQPOLE_GRID

Purpose


      Produce an equal area polar projection grid overlay

Explanation


      Grid is written on the current graphics device using the equal area
      polar projection. EQPOLE_GRID assumes that the output plot
      coordinates span the x and y ranges of -90 to 90 for a region that
      covers the equator to the chosen pole. The grid is assumed to go from
      the equator to the chosen pole.

Calling Sequence



      EQPOLE_GRID[,DLONG,DLAT,[/SOUTHPOLE, LABEL = , /NEW, _EXTRA=]

Inputs



      DLONG = Optional input longitude line spacing in degrees. If left
                out, defaults to 30.
      DLAT = Optional input lattitude line spacing in degrees. If left
                out, defaults to 30.

Input Keywords



      /SOUTHPOLE = Optional flag indicating that the output plot is
                        to be centered on the south rather than the north
                        pole.
      LABEL = Optional flag for creating labels on the output
                        grid on the prime meridian and the equator for
                        lattitude and longitude lines. If set =2, then
                        the longitude lines are labeled in hours and minutes.
      CHARSIZE = If /LABEL is set, then CHARSIZE specifies the size
                        of the label characters (passed to XYOUTS)
      CHARTHICK = If /LABEL is set, then CHARTHICK specifies the
                        thickness of the label characters (passed to XYOUTS)
      /NEW = If this keyword is set, then EQPOLE_GRID will create
                        a new plot, rather than overlay an existing plot.
      Any valid keyword to OPLOT such as COLOR, LINESTYLE, THICK can be
      passed to AITOFF_GRID (though the _EXTRA facility) to to specify the
      color, style, or thickness of the grid lines.

Outputs


      Draws grid lines on current graphics device.

Example


      Create a labeled equal area projection grid of the Galaxy, centered on
      the South pole, and overlay stars at specified Galactic longitudes,
      glong and latitudes, glat
      IDL> eqpole_grid,/label,/new,/south ;Create labeled grid
      IDL> eqpole, glong, glat, x,y ;Convert to X,Y coordinates
      IDL> plots,x,y,psym=2 ;Overplot "star" positions.

Copyright Notice



      Copyright 1992, The Regents of the University of California. This
      software was produced under U.S. Government contract (W-7405-ENG-36)
      by Los Alamos National Laboratory, which is operated by the
      University of California for the U.S. Department of Energy.
      The U.S. Government is licensed to use, reproduce, and distribute
      this software. Neither the Government nor the University makes
      any warranty, express or implied, or assumes any liability or
      responsibility for the use of this software.

Author And Modifications



      J. Bloch 1.4 10/28/92
      Converted to IDL V5.0 W. Landsman September 1997
      Create default plotting coords, if needed W. Landsman August 2000
      Added _EXTRA, CHARTHICK, CHARSIZE keywords W. Landsman March 2001



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