Name

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KDM_MAP_SCALE

Purpose

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  Provide a scale (legend) for a map

Category

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  Map, Imaging

Calling Sequence

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  KDM_MAP_SCALE

Keyword Parameters

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  X: location (in units [0,1]) of X position of scale
  Y: location (in units [0,1]) of Y position of scale
  HIGHLIGHT: Set this keyword to try to make the text stand out
              against the background of the map

Restrictions

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  Map coordinates must be defined (with, for example, MAP_SET)

Procedure

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  1) pick a point at (0.1, 0.1) from south west corner of map
  2) convert /norm coordinates to lat/lon
  3) pick a point at (0.3, 0.1) due east of first point
  4) convert /norm to lat/lon
  5) get distance between points in m
  6) find nearest round number of format [1-9][0*]
  7) find error between measured distance rounded goal number
  8) adjust second point by error
  9) repeat untill err < err_limit
  10) draw line from (x0,y0) to newly determined (x1,y0) location
    equal to nice round distance
  11) add legend

Example

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  map_set, 41, -74.5, /ortho, scale=3e6 ; near NY
  map_continents, /hi, /states, /US, color=254
  kdm_map_scale, x=0.1 ; explicitely set the X location
  OR
  map_set, /ortho, /iso ; the whole globe!
  map_continents
  kdm_map_scale, x=0.1, y=0.4 ; select X and Y locations

Modification History

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  Written by: Ken Mankoff, 2009.
  2010-02-02: KDM Added documentation.