idlastro / Astronomical Utilities: EQPOLE_GRID

[Source code]

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
This software has been authored by an employee or employees of Los Alamos 
National Security, LLC, operator of the Los Alamos National Laboratory (LANL) 
under Contract No. DE-AC52-06NA25396 with the U.S. Department of Energy.  The U.S.
Government has rights to use, reproduce, and distribute this software.  The public
may copy, distribute, prepare derivative works and publicly display this software 
without charge, provided that this Notice and any statement of authorship are 
reproduced on all copies.  Neither the Government nor LANS makes any warranty, 
express or implied, or assumes any liability or responsibility for the use of this
software.  If software is modified to produce derivative works, such modified 
software should be clearly marked, so as not to confuse it with the version 
available from LANL.
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