PROCESS WEIGHT (TRACE WEIGHTING, KILLING, REVERSING)

Parameters, alphabetically:
fno       hdr       ihdr      inverse   lhdr      lno
lprint    twp       type      w         weight    xwp

Document Date: 7 January 2007
Modifications:
    June 2006 - Add parameter TYPE and weighting by inverse standard deviation.
    Nov. 2005 - Change LNO to default to FNO (set to FNO on every list)

PROCESS WEIGHT weights individual traces by multiplying the entire trace
by a constant (scalar multiply).
     A weight of 1. Results in no amplitude change on the trace.
     A weight of 0. Results in the trace being killed.
     A weight of -1. Results in the trace being reversed in polarity.

All traces have a default weight of 1.  This means that only those
traces specified by the user will be weighted.  Weights are not
spatially varied, thus only those shots actually specified will be 
weighted.

Each parameter list must be terminated with the word END.  The entire
set of weight parameters must be terminated by the word END.


THE PARAMETER DICTIONARY
--- --------- ----------

FNO    - The first shot (or rp) to apply the weights to.  Shot (rp)
         numbers must increase monotonically.
         Preset = 1

LNO    - The last shot (rp) number to apply the weights to.  LNO must be
         larger than FNO in each list and must increase list to list.
         Default = FNO  (reset to FNO on each list unless LNO is given).

XWP    - Range-weight-pairs.  A list of range and weight pairs.  XWP
         must be given with increasing ranges.  The program computes the
         absolute value of both user ranges and data ranges.  
         e.g. xwp 1000 3.0 2000 0. - Traces with ranges exactly equal to
         1000 will be multiplied by 3, and traces with a range of
         exactly 2000 will be multiplied 0. (i.e. killed).  All other 
         traces will not be multiplied.
         Default = all 1.

TWP    - Trace number-weight-pairs. A list of trace numbers (of a shot
         or rp) and weights (listed in pairs).  ONLY THOSE TRACES
         SPECIFIED WILL BE WEIGHTED.  Trace numbers must increase
         within each list.   e.g.  twp 4 -1. 20 0. indicates that trace
         4 will be inverted in polarity and trace 20 will be killed.
         Default = all 1.

WEIGHT - The multiplier for all traces of the specified shot/rp (fno).
         The default value is 1., which means that the weight is applied
         to shot FNO to LNO, then reset to 1. (the default value).
         Default = 1.             e.g.    FNO 1234 weight 0 end

W      - An abbreviation for weight.  Equivalent to weight.
         Default = 1.       e.g. fno 1234 w -1 end

HDR    - Specifies the index of the SEG-Y trace header floating point word
         as the trace scalar multiplier.  Each trace is independent.
         e.g. hdr 55   causes every amplitude to be multiplied by the
         contents of the 55th floating point word in the SEGY trace header.

LHDR   - Specifies the index of the 32 bit integer SEG-Y trace header word
         as the trace scalar multiplier.  Each trace is independent.

IHDR   - Specifies the index of the 16 bit integer SEG-Y trace header word
         as the trace scalar multiplier.  Each trace is independent.

INVERSE - A YES/NO switch indicating that the inverse or reciprocal of
          the given weight should be used.  i.e. the multiplier becomes
          a divisor.
          Preset = no      e.g.  inverse yes

TYPE   - The type of weight to apply.
       = SDEV, The inverse of the standard deviation is used as a scalar
         multiplier for each trace.  
         Preset = not given (use w or weight)     e.g.  type sdev

LPRINT - Programmer's debug switch.
       = 8, The weight applied to each trace is printed.
       = 16, All the statisics are printed when TYPE SDEV is given.

END    - Terminates each parameter list.

Note *****
1)   In order to apply the same set of weights to all shots (rps), LNO
     must be set to a very large number. e.g.  LNO 32767
2)   a maximum of 100 twp or xwp pairs may be given.
3)   If multiple weights are give a a trace, they are multiplied together
     before the trace multiplication is performed.  E.G. if w 2 and type sdev
     results in a weight of 15, the total weigth applied is 30.


Example 1:
     process weight
          fno 0 lno 999999 xwp 1228 -1 1408 0 end
     end
Will reverse the polarity of all traces having a range of 1228, and will
kill all traces with a range of 1408, on shots (rps) 1 through 32767.

Example 2:
   Weight by offset (ala GECO)
procs  ....  header weight .....
header
   r60 = l10 + 6100    # 6100 is the far offset
   r59 = l10 / r60
   end
end
weight
   fno 0 lno 99999 hdr 59 end
end

Example 3:
   Weight by inverse standard deviation.
weight
   fno 0 lno 999999 type sdev end    # apply to ALL records 0-999999
end


Copyrighted (c) by:
Paul Henkart, Scripps Institution of Oceanography, November 1980
ALL RIGHTS RESERVED.