PROCEDURE/FUNCTION sd_latlt_grid :DESCRIPTION: Draw the latitude-longitude mesh with given intervals in Lat and LT. :KEYWORDS: dlat: interval in Latitude [deg]. If not set, 10 deg is used as default. dlt: interval in local time [hr]. If not set, 1 hour is used as default. :EXAMPLES: sd_map_set, /nogrid ;sd_map_set automatically calls sd_latlt_grid unless nogrid keyword is set. sd_latlt_grid, dlat=10., dlt=2. :AUTHOR: Tomo Hori (E-mail: horit@stelab.nagoya-u.ac.jp) :HISTORY: 2011/01/11: Created $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/sd_latlt_grid.pro $