Program:	tracks

Purpose:	Plots the track of a number of snips for a number
		of detectors.

Category:	IRAS

File:		tracks.c

Author: 	Fred Lahuis

Keywords:

	first the inputs on what should be displayed

    **IRSET=/IRDS=
		IRDS to be displayed.

(**)SNIP=	Snips to be displayed if none are		[all]
		entered via subsets.

(**)SDET=	Detectors to display if none are		  [0]
		entered via subsets.
		The default (0) corresponds to boresight.
		The boresight (0) cannot be entered via subsets,
		so if the boresight is wanted along with one or
		more detectors it has to be entered with SDET.

    COOR=	Coordinate system.			  [IRDS-coor]

    PROJ=	Projection type.			     [GNOMON]
		Entering an unknown type gives a list of possible
		projection types.

    POS=	Positions to be plotted, in		       [none]
		the coordinate system given at COOR.

  **CENTRE=/CENTER=
		lon & lat of plot center.		[IRDS-center]
		If a position is entered by the user it must be
		given in the coordinate system as given by COOR.

  **PRCEN=	Projection center.			[plot centre]

  **SIZE=	lon & lat size of the irds plate	  [IRDS-size]
		to be plotted, with respect to the plot centre.

	inputs on what the physical plot should look like

    GRDEVICE=	Graphics device.		     [list of options]

  **BOX=	The area out of the irds-plate		       [N/[Y]]
		at the chosen plot centre and size is drawn in the
		plot.

  **CHARSIZE=	Character sizes of the different	    [defaults]
		items in the plot.
		The defaults are given in the output area.
		The entries are in order:
			axis labels, coordinate labels,
			track labels, IR_Gipsy vignet,
			program id., info text.

  **FIRSTPOS=	The value of the first coordinate tick (the coordinate
		with the lowest value). The coordinates should be entered
		as e.g. 3d15m30 or 3h15m30.
		If one value is entered it is used as the first position
		for both x-axis. If two are entered the first is used
		for both x-axes and the second for both y-axes. If three
		are entered the last is used for both y-axes.

  **LINEW=	Width of the lines in units of pgplot's        [1,1,1]
		default linewidth. The first entry is used for the box,
		the second for the tracks and the last for all
		printed text.

  **LOOP=	Default TRACKS loops over	       [sdet/snip/no]
		the detectors if more than one snip is given,
		or one snip and one detector, i.e. that for each
		detector all given snips are plotted in a separate
		plot.
		If one snip is given and more than one detector
		the detectors for the snip are plotted, unless
		`sdet` is given as the argument for LOOP.
		If `sdet` is entered all snips are plotted for each
		detector in a single plot.
		If `snip` is entered the given detectors are plotted
		for each snip.
		IF `no` is entered all tracks for all given snips and
		detectors are plotted in one single plot.

  **NTICK=	Number of coordinate ticks for each	[4,4,4,4]
		axis. The first two are for the both longitude axes
		and the last two for both latitude axes.
		If two values are entered the first is assumed to
		be for the longitude axes and the second for both
		latitude axes.


  **PLOTEDGE=	Offset in cm of the lower and left axis with respect
		to the sides of the plot.

  **PLSIZE=	Size of the plot in centimeters.	     [default]
		The size corresponds to the area defined by SIZE,
		which is plotted as a dotted box if BOX=y.
		If a value is given here SCALE has no effect.

  **PROMPT=	Ask the user to plot the next page every time	N/[Y]
		during a loop (NEXTPAGE=).
		This keyword can be entered and thus changed at any
		time during a loop.
		See also LOOP.

(**)SCALE=	Scale of the plot in			 ['lon','lat']
		arcseconds per millimeter for longitude and latitude
		in the plate coordinate system.
		This keyword is not asked and has no effect if a
		physical size for the plot has already been given
		with PLSIZE.

  **TICK=	Separation between ticks (in the chosen coordinate
		system). The calculated defaults are shown in the
		output area. The separation should be entered
		as e.g. 3d15m30 or 3h15m30 or 3.5d or 3d10.5m.

  **VIGNET=	Plot an IR-Gipsy vignet.		       [Y/(N)]

  **FILENAME=	Give name for (CPLOT) recall file:	     [No file]
		Store start and end points (in degrees)
		of the plotted tracks in a file. This Ascii file can
		be used as a recall file for the CPLOT keyword PLLINE=
		CPLOT does not clip lines, so let TRACKS take care of
		the the right center (CENTER=) and size (SIZE=).

Description:

Comments:	Coordinates:
		      If an area near the pole is used, the plotted
		      coordinates are not to be trusted.
		Inputs:
		      Details on the input format of physical
		      coordinates can be found in the documentation of
		      the subroutine userangle.
		Track numbering:
		      The snip and or sdet numbers are plotted at the
		      start of each track.

Updates:	Jan  8 1992: FL  Document created.
		Sep 29 1992: FL  Minor changes and update documentation.
		Nov 13 1992: FL  Coordinate labeling highly improved.
		Jan 20 1993: VOG Keyword FILENAME= added.
		Mar  9 1993: FL  Correct direction longitude coordinates.
		Sep 17 1993: FL  Bug in coordinate plotting on HP's
				 localized and killed.
		Apr 14 1994: FL  HP bug fixed.
		Jul 20 1999: DK  Cstring[12] extended to 1000; they were
				 too short. Thanks Tin Kam Ho