UVPLOT


UVPLOT is a program to plot the u,v coverage of a real observation  in
a  format  similar to a HAZI plot (q.v.).  One dot is plotted for each
(non-deleted) data point in a MERGE-format file.  Both MERGE-formats 1
and 2 are accepted.  Contours of visibility amplitude (computed from a
source model) can be superimposed on the (u,v)-tracks.


Example

The following examples produce a PostScript plot file.

$! VMS                            # UNIX
$ UVPLOT                          uvplot <<EOD
  Input = [TJP.MAR79]1633.MRG       Input = tjp/mar79/1633.mrg
  Plotf = uvplot.ps/vps             Plotf = uvplot.ps/vps
  Umax = 150e6  Vmax = 150e6        Umax = 150e6   Vmax = 150e6
  Label                             Label
  /                                 /
$ PRINT/Q=LW UVPLOT.PS            EOD
                                  lpr -Pps uvplot.ps



Parameters

All the parameters except INPUT are optional.  The parameter names can
be  abbreviated  (minimum  match).   End the list of parameters with a
slash (/) or end-of-file (control-Z in VMS, control-D in UNIX).

INPUT = "filename" :  the filename of  the  input  MERGE-format  file.
          This parameter must be specified.

PLOTFILE = "device/type" :  any valid  graphics  device  specification
          may be supplied, e.g., "TTA4:/TEK" for a Tektronix terminal,
          "/G" for a Grinnell, "/VT" if  your  terminal  is  a  VT125,
          "UVDIST.PLT/VPS"   for  a  LaserWriter  file.   The  default
          destination for the plot file is the  logical  name  TEKTERM
          which is defined in the VLB LOGIN.COM file.  The plot can be
          suppressed entirely by specifying PLOTFILE=/NULL.

UMAX = 2E8 :  sets the maximum value for the u-axis,  in  wavelengths.
          If UMAX is not supplied, it is taken from the data.

VMAX = 1.6E7 :  sets the maximum value for the v-axis, in wavelengths,
          like UMAX.  UMAX and VMAX can be used to control how much of
          the (u,v)-plane is plotted.

LABEL :   If specified, UVPLOT marks the first point on each  baseline
          with a label (the initial letters of the two stations).

MARK = 12 :  Specifies the symbol to be used for plotting  each  (u,v)
          point.   The  default  is -1, which gives a single dot.  See

UVPLOT                                                            Page 2


          PGPLOT documentation for the full symbol repertoire.

NOINVERT :   If  specified,  suppresses  the  plot  of  the  conjugate
          (u,v)-points.

MODEL = "file" :   Specify  the  name  of  a  model  file  from  which
          visibility contours will be computed.

CONTOURS = x1,x2,...  :  Specify up  to  20  contour  levels  for  the
          visibility  amplitude  contours, in Janskys.  If no contours
          are specified, none will be plotted.

LINEWIDTH = n :  use this parameter to draw heavier  lines,  e.g.,  on
          the  Versatec plotter.  The default line-width is 1 (pixel);
          values up to 21 are allowed.  LINEWIDTH=3 usually gives good
          results on the Versatec plotter.

FONT = n :  specifies the character font to be used for labelling  the
          graph.   The  default (1) gives a simple font; other options
          are 2 (roman), 3 (italic), and 4 (script).

DOTSIZE = n :  Specify the pen size for drawing the symbols  used  for
          each (u,v)-point.  If DOTSIZE is not specified, the pen size
          specified by LINEWIDTH is used.

COUNT :   If specified, the number of datapoints on each  baseline  is
          typed out after the total number of points and mean epoch.

COLORS = n1, n2, n3, n4, n5  :   This  optional  parameter  gives  you
          complete  control  over  the  colors used when plotting on a
          color device.  The  parameters  are  "color  indices"  (0  =
          background  color, 1 = black [white on TVs], 2 = red, etc.):
          see the PGPLOT documentation for more details.   n1  is  the
          color  used  for the box and axes (default 5 = cyan), n2 for
          the annotation (default 5 = cyan),  n3  for  the  visibility
          points  (default 3 = green), n4 for the conjugate visibility
          points (default 2 = red), and  n5  for  the  model  contours
          (default 4 = blue).

NOTEXT :  If specified, the file name and modification date  will  not
          be written on the plot.


Model Contours

The (u,v) plane is the conjugate (Fourier transform) of the sky plane.
When you request contours of a model, UVPLOT computes the amplitude of
the model, i.e., the model visibility, at a number  of  gridpoints  in
the  (u,v)  plane,  and contours the resulting function.  The contours
are lines of equal model  visibility  amplitude  (or  correlated  flux
density).   This  may  or may not be useful!  If you plot contours of,
say, a double model, you should be able to  identify  the  crests  and
troughs  of  the  visibility  function running across the (u,v) plane:
where these intersect the plotted (u,v) tracks is a good place to look
for maximum or minima in the data (using VISPLOT).  Usually it is more

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useful to use VISPLOT to compare data and  model,  but  sometimes  the
contouring  option  in  UVPLOT  is  useful,  e.g., to see if important
features in the model visibility coincide with  unsampled  regions  in
the (u,v) plane.


Limitations

The program accepts input files containing (a) 40 or  fewer  stations,
(b)  50,000  or fewer (non-deleted) u,v-points.  These limits can only
be changed by re-compiling the program.


History

Version 1.0:  1979 Sep 22 - new program (T.J. Pearson).
Version 1.1:  1980 Mar 13
Version 1.2:  1980 Jun 30 - extended to 15 stations (TJP).
Version 1.3:  1980 Oct 17 - parameters UMAX, MARK added (TJP).
Version 2.0:  1981 May 21 - adopt Fortran 77 standards, new plot
                            format (uses PGPLOT package), new
                            parameter NOINVERT (TJP).
Version 3.0:  1981 Jun 12 - add model amplitude contours (TJP).
Version 3.1:  1982 Jun  8 - new graphics devices (TJP).
Version 3.2:  1982 Oct  7 - LINEWIDTH parameter (TJP).
Version 4.0:  1983 Jul  5 - extend to include MERGE-format 2 and
                            orbiting VLBI stations (D.L. Meier).
Version 4.2:  1983 Aug 19 - add per baseline count to output (TJP).
Version 4.3:  1983 Sep 20 - increase to 20 stations; increase MAXP to
                            50,000 UV points (DLM).
Version 4.4:  1984 Mar 29 - make missing coordinates non-fatal (TJP).
Version 4.5:  1984 Oct  1 - Issue an explicit message if there are no
                            data in the dataset, instead of crashing
                            (TJP).
Version 4.6:  1984 Nov 28 - Add COLORS parameter (TJP).
Version 4.7:  1986 Jan  7 - Update to reflect latest PGPLOT (TJP).
Version 4.8:  1986 Feb 17 - Show file modification date on plot (TJP).
Version 5.0:  1986 Nov 14 - All input is now parameters (TJP).
Version 5.1:  1987 Jan 14 - Fix bug in LIST option (TJP).
Version 5.2:  1987 Aug 29 - Prompt before drawing plot if plotting on
                            user's terminal (TJP).
Version 5.3:  1988 Apr  2 - Minor changes for Convex (TJP).
Version 5.4:  1988 Jun 24 - Add NOTEXT parameter (Tasso Tzioumis) and
                            use VLBOPE routine (TJP).
Version 5.5:  1988 Jul 19 - Choose frequency unit intelligently; use
                            GETCOM routine (TJP).
Version 6.0:  1989 Mar 22 - Remove LISTFILE option; add LABEL option
                            (TJP).
Version 6.1:  1989 Dec 20 - Correct dimension error (TJP).
Version 6.2:  1991 Mar 21 - Increase to 40 stations (TJP).