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FIXED_MAP_GRID

FIXED_MAP_GRID

Name


  FIXED_MAP_GRID

Purpose


      The MAP_GRID procedure draws the graticule of parallels and meridians,
  according to the specifications established by MAP_SET. MAP_SET must be called
  before MAP_GRID to establish the projection type, the center of the
  projection, polar rotation and geographical limits.

Category


  Mapping.

Calling Sequence


      MAP_GRID

Inputs


  NONE

Optional Inputs


  NONE

Keyword Parameters



  BOX_AXES: Surround the map window with a "box" style axes with
        annotations, outside the box, where the parallels intersect the
        sides, and the meridians intersect the bottom and top edges of the
        box. The border of the box is drawn in alternating foreground and
        background colors, with color changes at each intersection with
        a parallel or meridian. This keyword determines the thickness of
        the box's border, in millimeters. If LABEL is not explicitly
        specified, it defaults to 1 when this keyword is present. If this
        feature is selected, be sure to leave enough room around the map
        window for the annotation, usually by specifying the XMARGIN and
        YMARGIN keywords to MAP_SET. See the example below.
  CHARSIZE: The size of the characters used for the labels. The default is 1.
      COLOR: The color index for the grid lines.
FILL_HORIZON: Fills the current map_horizon.
    HORIZON: Draws the current map horizon.
  INCREMENT: Determines the spacing between graticle points.
  GLINESTYLE: If set, the line style used to draw the grid of parallels and
            meridians. See the IDL User's Guide for options. The default is
            dotted.
  GLINETHICK: The thickness of the grid lines. Default is 1.
      LABEL: Set this keyword to label the parallels and meridians with their
            corresponding latitudes and longitudes. Setting this keyword to
            an integer will cause every LABEL gridline to be labeled (i.e,
            if LABEL=3 then every third gridline will be labeled). The
            starting point for determining which gridlines are labeled is the
            minimum latitude or longitude (-180 to 180), unless the LATS or
            LONS keyword is set to a single value. In this case, the starting
            point is the value of LATS or LONS.
  LATALIGN: This keyword controls the alignment of the text baseline for
            latitude labels. A value of 0.0 left justifies the label,
            1.0 right justifies it, and 0.5 centers it.
    LATDEL: The spacing in degrees between parallels of latitude in the grid.
            If not set, a suitable value is determined from the current map
            projection.
      LATS: The desired latitudes to be drawn (and optionally labeled). If
            this keyword is omitted, appropriate latitudes will be generated
            with consideration of the optional LATDEL keyword. If this
            keyword is set to a single value, drawn (and optionally labeled)
            latitudes will be automatically generated as
            [...,LATS-LATDEL,LATS,LATS+LATDEL,...] over the extent of the
            map. The single valued LATS is taken to be the starting point
            for labelling (See the LABEL keyword).
    LATLAB: The longitude at which to place latitude labels. The default is
            the center longitude on the map.
  LATNAMES: An array specifing the names to be used for the latitude labels.
            By default, this array is automatically generated in units of
            degrees. This array can be a string array or numeric, but should
            not be of mixed type. When LATNAMES is specified, LATS must also
            be specified, but the number of elments in the two arrays need not
            be equal. Extra LATNAMES are ignored, while LATNAMES not supplied
            are automatically reported in degrees. LATNAMES can be used when
            LATS is set to a single value. It this case, the LATS used will
            start at the specified latitude and progress northward, wrapping
            around the globe if appropriate. Caution should be used when
            using LATNAMES in conjunction with a single LATS, since the
            number of visible latitude gridlines is dependent on many factors.
  LONALIGN: This keyword controls the alignment of the text baseline for
            longitude labels. A value of 0.0 left justifies the label,
            1.0 right justifies it, and 0.5 centers it.
    LONDEL: The spacing in degrees between meridians of longitude in the grid.
            If not set, a suitable value is determined from the current map
            projection.
    LONLAB: The latitude at which to place longitude labels. The default is
            the center latitude on the map.
      LONS: The desired longitudes to be drawn (and optionally labeled). If
            this keyword is omitted, appropriate longitudes will be generated
            with consideration of the optional LONDEL keyword. If this
            keyword is set to a single value, drawn (and optionally labeled)
            longitudes will be automatically generated as
            [...,LONS-LONDEL,LONS,LONS+LONDEL,...] over the extent of the map.
            The single valued LONS is taken to be the starting point for
            labeling (See the LABEL keyword).
  LONNAMES: An array specifing the names to be used for the longitude labels.
            By default, this array is automatically generated in units of
            degrees. This array can be a string array or numeric, but should
            not be of mixed type. When LONNAMES is specified, LATS must also
            be specified, but the number of elments in the two arrays need not
            be equal. Extra LONNAMES are ignored, while LATNAMES not supplied
            are automatically reported in degrees. LONNAMES can be used when
            LONS is set to a single value. It this case, the LONS used will
            start at the specified longitude and progress eastward, wrapping
            around the globe if appropriate. Caution should be used when
            using LONNAMES in conjunction with a single LONS, since the number
            of visible longitude gridlines is dependent on many factors.
  MAP_STRUCTURE: Set this keyword to a !MAP structure, as returned from
      MAP_PROJ_INIT. If this keyword is set then the gridlines are passed
      through MAP_PROJ_FORWARD and the resulting lines are drawn using
      Cartesian coordinates. If this keyword is not set then it is assumed
      that MAP_SET has been called to set up a map projection.
  NO_GRID: Set this keyword if you only want labels but not gridlines.
ORIENTATION: Specifies the clockwise angle in degrees from horizontal
            of the text baseline that the labels should be rotated. Note,
            that the rotation used in MAP_SET is also clockwise, but XYOUTS
            is normally counterclockwise.
  T3D: Set this keyword to indicate that the generalized transformation
      matrix in !P.T is to be used. If not present, the user-supplied
      coordinates are simply scaled to screen coordinates.
  ZVALUE: Sets the Z coordinate, in normalized coordinates in the
        range of 0 to 1, at which to output the continents.
      Note - This keyword has effect only if keyword T3D is set and the
        transformation is stored in !P.T

Outputs


        Draws gridlines and labels on the current map.

Example


    map_set,10,20,23.5,/cont,/ortho,/horizon ; establish a projection
        lats=[-65,-52,-35,-20,-2.59,15,27.6,35,45,55,75,89]
                    ; choose the parallels to draw
        map_grid,lats=lats,londel=20,lons=-13,label=2,lonlab=-2.5,latlab=7
                    ;draw the grid
  Make a map with a grid surrounded by a box style axis:
  map_set, /STEREO, 40, -90,scale=50e6,/CONTINENTS, XMARGIN=3, YMARGIN=3
  map_grid, /BOX_AXES, COLOR=3, CHARSIZE=1.5 ;

Modification History


  Written by: SVP, May, 23 1996.
  DMS, Feb, 1996 Note that this version plots all gridlines
          unless a 4 element LIMIT was specified to MAP_SET.
      SVP, Nov 1996 Changed over !map1 (new IDL5 maps)
  SVP, May 1996 Map_Grid used to live inside of map_set.pro, now
                      it lives here.
      SVP, May 1996 Changed LABEL to determine the skip between labelled
                      gridlines.
                      Also, added the LATS and LONS keywords to give complete
                      control over where the labels go.
      SVP, Sept 1996 Added LATNAMS,LONAMES, and ORIENTATION keywords
  DMS, Nov, 1996 Rev 2 of maps.
  DMS, Jul, 1997 Added Box Axes
  CT, Jan 2004: Added MAP_STRUCTURE keyword.
  Renamed the function FIXED_MAP_GRID with fixed at lines 555-556 and
      664-665 as described here: http://www.dfanning.com/map_tips/missinggrid.html.
      This is required to get proper grid output in some applications, but
      it breaks other code.



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