PRO overlay_map_vec :Description: Draw lines from a start point [lat0,lon0] with a direction [dlat,dlon] and arclength in degree on the plot window set up by sd_map_set. :Params: lat0: latitude of the start point [deg] lon0: longitude of the start point [deg] dlat: the latitudinal component of the vector to be drawn (positive: north) dlon: the longitudinal component of the vector to be drawn (positive: east) arclength: length of the vector in degree with which the vector is drawn. dlat and dlon are normalized by this value. Thus the absolute values of dlat and dlon are ignored. Only the ratio is concerned. :Keywords: linethick: Set a value of line thickness color: Set a value of color table with which the lines are drawn :Examples: ex) overlay_map_vec, 65., 270., 1.,-3, 18., linethick=1.5 :History: 2013/10/02: Initial release :Author: Tomo Hori (E-mail: horit at stelab.nagoya-u.ac.jp) $LastChangedBy: jwl $ $LastChangedDate: 2014-02-10 16:54:11 -0800 (Mon, 10 Feb 2014) $ $LastChangedRevision: 14265 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/erg/ground/radar/superdarn/overlay_map_vec.pro $