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                        Program OVERLAY

Date:  May 1999

   Usage:   overlay -pv inputfile fno [dot_color dot_size ltr] < overlay-file 
   -p = travel time picks
   -v = sioseis style vtp velocities

   Overlay a SIOSEIS plotfile with travel-time curves or "picks".

   SIOSEIS plotfiles are simply a sequential series of raster lines.
A raster is a dot made by a pen.  A raster line is a series of rasters
in the direction the pen moves, which in seismic plots is "down the
trace".  There are dpi dots per inch, where dpi is defined by the
SIOSEIS parameter NIBS.

   SIOSEIS rasterfiles have a limited header so the user must redefine
several plot parameters.  The sense of a seismic trace is missing
from rasterfiles.  Rasterfiles have raster lines rather than seismic
traces and the annotation of the seismic plot is lost.  The seismic
plot vertical scale (VSCALE) is retained, as is the horizontal scale

   In order to associate raster lines with the seismic travel-times or
picks, each raster line is numbered starting with FNO.  Successive 
raster lines are calculated using the horizontal scale retained from
the raster file.  HSCALE is used if it was given, otherwise TRPIN is
used.  E.G.  If the HP DesignJet is used, then there is a raster line 
every 1/300 inches (dots per inch = 300).  When physically in front
of the DeisgnJet, with the front control panel to your right, then
the right side on the plotter is "the top" and the left side is the
bottom.  The first trace plotted is then on the right hand side of
the paper as the paper is moved through the plotter.

   Program OVERLAY reads STDIN for the overlay parameters, thus the
above notation "< overlay-file" means that the overlay parameters will
be read from a file named "overlay-file".

inputfile - The SIOSEIS rasterfile to be overlaid.  The rasterfile
      may be overlain multiple times.

fno - The first number.  The raster line of the center of the first
      plot trace is numbered FNO.  Subsequent raster lines are
      numbered by DPI/TRPIN or DPI/HSCALE.  The pick or velocity value
      associated with the raster line is obtained from STDIN (the

dot_color - The color or the overlay.  Allowable colors are:
      Preset = BLACK

dot_size - The width of each point in the overlay.
     Preset = 3

ltr - If the sioseis plot parameter DIR LTR was given, then this
      parameter must be used in program overlay.  The default SIOSEIS
      plot is when the right side of the seismic plot is plotted first
      or from right to left.  Refraction or OBS/OBH plots use parameter
      LTR so that time is reversed from reflection plots.

overlay -p part1 41480 black 8 ltr < ryan

where file ryan is:
fno 41531 picks 0.042 end
fno 41532 picks 0.064 end
fno 41533 picks 0.082 end
fno 41534 picks 0.114 end
fno 41535 picks 0.136 end
fno 41536 picks 0.168 end
fno 41537 picks 0.197 end
fno 41538 picks 0.224 end
fno 41539 picks 0.256 end
fno 41540 picks 0.280 end
fno 41541 picks 0.299 end


------- --- -------
    The VTP overlay creates a velocity vs time plot from a
file containing a set of velocity-time pairs (VTPS) in the 
SIOSEIS style used by NMO.  The entire NMO script may be used
since overlay scan for the keyword VTP.
    Time and spatial variation is performed, so the resulting
plot is very dense.
    The overlay parameters are similar to those used by SIOSEIS
process NMO.  An entire SIOSEIS script file may be used!

FNO - The trace number associated with VTP.  The plot distance is
      computed using (FNO - fno), where the lowercase fno is the
      number given on the overlay program line.