GDPLOT2 draws contour lines through scalar grids and/or wind
        barbs or arrows or streamlines through vector grids.
	Multiple sets of contours, vectors and/or streamlines
	can be generated for each frame.

INPUT PARAMETERS
 
    GDFILE    Grid file
    GDATTIM   Grid date/time
    GLEVEL    Grid level
    GVCORD    Grid vertical coordinate
    PANEL     Panel loc/color/dash/width/regn
    SKIP      Skip_cntr/skip_plt_x;skip_plt_y
    SCALE     Scalar scale / vector scale
    GDPFUN    Scalar grid or vector grid function
    TYPE      GDPLOT2 function processing type
    CONTUR    Subbox/smooth
    CINT      Contour interval/min/max
    LINE      Color/type/width/label/smth/fltr/scflg
    FINT      Fill interval/min/max
    FLINE     Fill colors/fill types
    HILO      Color/symbol/rng/rad/cnt/intp
    HLSYM     HILO txt size/posn/font/wdth/hw
    CLRBAR    Color/ornt/anch/x;y/ln;wd/freq|text_info
    WIND      Wind symbol/siz/wdth/typ/hdsz
    REFVEC    Mag;x;y;txtsiz/font/wdth/HW;labl
    TITLE     Title color/line/title
    TEXT      Size/fnt/wdth/brdr/N-rot/just/hw flg
    CLEAR     Clear screen flag
    GAREA     Graphics area
    IJSKIP    Iskp;Istrt;Istp/Jskp;Jstrt;Jstp
    PROJ      Map projection/angles/margins|drop flag
    MAP       Map color/dash/width/filter flag
    MSCALE    fgc;bgc;mask/units/lat;hide/values/anch/x;y/ln;wd/freq|text_info|t
    LATLON    Line color/dash/width/freq/inc/label/format
    DEVICE    Device|name|x size;y size|color type
    STNPLT    Txtc/txt attr|marker attr|stnfil#col
    SATFIL    Satellite image filename(s)
    RADFIL    Radar image filename(s)
    IMCBAR    Color/ornt/anch/x;y/ln;wd/freq
    LUTFIL    Enhancement lookup table filename
    STREAM    lines/arrows/stop/slow/scale
    POSN      Position / Text format
    COLORS    Color list
    MARKER    Marker color/type/size/width/hw
    GRDLBL    Grid point label color
    FILTER    Filter data factor
 
 

PROGRAM DESCRIPTION
 
    GDPLOT2 draws contours through scalar grids and streamlines
    wind barbs or arrows at grid points for vector grids.  Plots
    are generated for any field computed using the GEMPAK grid
    diagnostic functions.  The program can generate multiple
    sets of scalar and vector plots for each frame.

    GDPLOT2 can also generate plots for multiple times.  The
    list of times may be given in GDATTIM allowing animation.

    Exclamation points are used in GDPFUN to delimit multiple overlays
    of scalar and vector fields, respectively.  All other parameters
    (except DEVICE, CLEAR and LUTFIL) may contain exclamation points
    to delimit specifications for the fields defined by GDPFUN.  If
    any parameter contains more specifications than the maximum number of
    plots specified in GDPFUN or GDFILE, they will be ignored.  Positions
    between exclamation points may be left blank.  Most parameters
    will replace the blank with the previous value (repeat).  A trailing
    exclamation point will be treated as a blank.  If there is no
    trailing exclamation point, the last specification will be repeated
    for subsequent plots.

	SCALAR QUANTITIES

    Scalar contours may be displayed as lines or as a color fill.
    If TYPE is C, contour lines are drawn using input from CINT
    and LINE.  If TYPE is F, filled contours are drawn using
    specifications from FINT and FLINE. Both contour lines and
    filled contours are drawn if TYPE is F/C or C/F.

    Scalar grid point values may also be plotted by specifying TYPE
    to be P.  If TYPE M is also specified, then markers will be plotted
    at the grid point locations according to the MARKER parameter.
    The value's location relative to the actual grid point location
    is set by the POSN parameter.

    All scalar types ( C, F and P) may be requested at
    one time, e.g., TYPE=C/F/P.  The order is irrelevant, however,
    contour fills (F) will be done first followed by contour
    lines (C), the map background, grid point indices (M), markers (G)
    and values (P).

    The attributes of the contour lines, including the color,
    line type, line width, and label frequency are specified
    in LINE.  The four attributes must be separated with slashes;
    semicolons separate the values for each attribute.  If the
    line type is set to a single negative number, negative
    contour values will have the absolute value of the line type
    and positive values will be solid.  If the label type is set
    to a single number, n, then every nth value will be labeled.

    The contour fill intervals are specified in FINT; the attributes
    for the fill are specified in FLINE.  The first color specified
    in FLINE fills values less than the first level; while the
    last color fills values greater than the last level.  Therefore,
    n levels require n+1 colors.

    A range of colors may be specified in either FLINE or LINE by
    specifying starting, ending and increment values in that order
    separated by dashes.  If the increment is missing, a default
    of 1 is used.

    The fill type may be set to 1 (solid), 2 (slanted dash) or 3
    (slanted line).  If fill type is set to 0, solid fill is used.
    If the fill type is set to a single negative number, negative
    values will use the absolute value of the fill type, and positive
    values will be solid.

    For contours, SKIP specifies the number of grid points to skip
    in generating contours.  For example, if SKIP = 1, every other
    point is used to generate the contours.

    The HILO and HLSYM parameters control marking and labeling the
    values of relative maxima and minima.  CLRBAR allows a color bar
    to be added for color fill contours. IMCBAR allows a color bar
    to be added for images.

	VECTOR QUANTITIES

    Vector grids may be displayed as either a field of wind barbs
    or arrows, or as a streamline display.  If TYPE is A, wind arrows
    will be displayed; if TYPE is B, wind barbs will be displayed.
    If both A and B are specified, B will prevail.
    If TYPE is N and neither A nor B is also indicated, then non-unit
    wind barbs will be assumed.  If TYPE is N in combination with either
    A or B, then non-unit arrows or barbs, respectively, will be plotted.
    If TYPE is S, streamlines will be drawn.

    As with scalar functions, the order of the TYPE values is irrelevant.
    The order of plotting is the map background, grid point indices (G),
    markers (M), vector arrows/barbs (A or B) and streamlines (S).

    Winds will be displayed in m/s, unless the KNTV operator has been
    specified in GDPFUN, in which case the winds will be displayed
    in knots.

    For vectors, SKIP specifies the number of points to skip in both
    coordinate directions.  For example, SKIP = /1;2 will display winds
    at every other grid point in the x direction and every third grid
    in the y direction.  SKIP = /0 displays winds at every grid point.
    Wind barbs or arrows can also be staggered by specifying negative
    values for SKIP.

    The FILTER parameter filters gridded wind arrows/barbs in the same
    way as it filters station models in the program SFMAP.  If
    FILTER=yes, the default filter value is set to 1.0.  If FILTER=no,
    then the SKIP parameter is used to filter the winds.  Otherwise
    FILTER is expected to be a numeric value greater than zero which
    controls the density of plotted winds.

	MISCELLANEOUS

    Grid point markers may be plotted by setting TYPE=M along with
    either a scalar TYPE or vector TYPE and valid GDPFUN.
    Marker attributes will be determined via the MARKER parameter.

    Grid index values ( row and column numbers ) may be plotted by
    setting TYPE=G along with either a scalar TYPE or vector TYPE and
    valid GDPFUN.  Attributes will be determined via the GRDLBL parameter.

    Station locations and identifiers may be plotted using the
    STNPLT parameter.


EXAMPLES
 
    1.  Plot the 700 mb temperature, dewpoint and wind barbs.  Plot the
	temperature in color 3 and the dewpoint in color 17.  For both
	sets of contours, the lines of negative value are drawn in
	pattern 3 and the those of positive value are solid.  Every other
	contour is labeled.  The wind barbs are plotted in m/s in color 6
	and are filtered according to the FILTER value.
	The display area is an enlarged area centered on New York.

	GDFILE	 =  $GEMPAK/data/hrcbob.grd
	GDATTIM	 =  f24
	GLEVEL	 =  700
	GVCORD	 =  pres
	PANEL	 =  0
	SKIP	 =  0
	SCALE	 =  0
	GDPFUN	 =  tmpc        ! dwpc       ! wnd
	TYPE	 =  C           !            ! B
	CONTUR	 =  3
	CINT	 =  2           ! 5
	LINE	 =  3/-3/3/2    ! 17/-3/2/2
	FINT	 =  0
	FLINE	 =  10-20
	HILO	 =
	HLSYM	 =
	CLRBAR	 =
	WIND	 =  bm6//2
	REFVEC	 =  10
	TITLE	 =  1/-2/~  @  TEMPERATURE, DEWPOINT AND WIND ! 0
	TEXT	 =  1/22//hw
	CLEAR	 =  yes
	GAREA	 =  ny-
	PROJ	 =  mer
	MAP	 =  1/7
	LATLON	 =  2/10/1/1/5;5
	DEVICE	 =  xw
	STNPLT   =
	SATFIL	 =
	RADFIL   =
	IMCBAR   =
	FILTER   =  1.2

    2.  Draw fills and contours of the magnitude of the wind (knots),
	contours of height and wind barbs (knots) at 250 mb and
	plots the value of the wind magnitude at the grid points.
	Winds are filtered according to the FILTER value.
	The contour and fill intervals are specified in CINT and FINT.
	The display area is the entire grid on a stereographic map.

	GDFILE	 =  $GEMPAK/data/hrcbob.grd
	GDATTIM	 =  f24
	GLEVEL	 =  250
	GVCORD	 =  pres
	PANEL	 =  0
	SKIP	 =  0/1
	SCALE	 =  0                       ! -1
	GDPFUN	 =  knts(mag(wnd))          ! hght      ! kntv(wnd)
	TYPE	 =  c/f/p                   ! c         ! b
	CONTUR	 =  1
	CINT	 =  30;50;70;90;110;130;150 ! 12
	LINE	 =  27/5/2/1                ! 20/1/2/1
	FINT	 =  70;90;110;130;150
	FLINE	 =  0;25;24;29;7;15
	HILO	 =
	HLSYM	 =
	CLRBAR	 =  1
	WIND	 =  bk18//1
	REFVEC	 =
	TITLE	 =  5/-2/~  @  HEIGHTS, ISOTACHS AND WIND (KTS) ! 0
	TEXT	 =  1/21//hw
	IMCBAR   =
	CLEAR	 =  yes
	GAREA	 =  grid
	PROJ	 =  str/90;-105;0
	MAP	 =  1
	LATLON	 =  0
	DEVICE	 =  XW
	STNPLT   =
        SATFIL   =
        RADFIL   =
        IMCBAR   =
	FILTER   =  yes

ERROR MESSAGES
 
    [GDPLOT2  +2]   The requested scalar/vector cannot be computed.
    [GDPLOT2  +1]   WARNING.  There are no contour levels.
    [GDPLOT2  -1]   Fatal error initializing TAE.
    [GDPLOT2  -2]   Fatal error reading TAE parameters.
    [GDPLOT2  -3]   Fatal error initializing GEMPLT.
    [GDPLOT2  -4]   Grid requested is not available.
    [GDPLOT2  -5]   Error setting grid navigation for file ....
    [GDPLOT2  -6]   There are no grids in grid file.