Name

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KDM_NORTH

Purpose

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  This procedure puts a North arrow (and letter N) on a map
  indicating which way is North.

Category

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  Map, Imaging

Calling Sequence

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  KDM_NORTH

Keyword Parameters

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  LON: The desired longitude of the tail of the arrow
  LAT: The desired latitude of the tail of the arrow

Side Effects

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  Draws an arrow and the letter "N" on the current map display

Restrictions

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  Must have a map projection set up (for example, with MAP_SET)

Procedure

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  1) Find the lat/lon bounds of the map
  2) If no lat/lon for arrow tail specified, then use the point at
    (0.2, 0.8) (where (0,0) is the bottom left and (1,1) is the top
    right corner of the map)
  3) Calculate an offset so the arrow is 10% of the map
  4) Convert the head and tail to a great circle path (map_2points)
  5) Plot it, add the arrow, and add the letter "N"

Example

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  MAP_SET, /MOLLWEIDE, 40,-50, /GRID, SCALE=75e6,/CONTINENTS
  map_continents
  map_grid, glinestyle=0, color=254
  kdm_north, color=253, thick=4, charth=4 ; default location
  KDM_NORTH, lon=0, lat=0 ; at (0,0)

Modification History

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  Written by: Ken Mankoff, 2009-02.
  2010-02-02: KDM Added documentation. Fixed bug where setting lat=0
                  or lon=0 used default location instead.