NAME

     davc - apply an automatic gain control to trace data

SYNOPSIS

     davc [ -Nntap ] [ -Ootap ] [ -nsns ] [ -nene ] [ -rsirs ]  [
     -reire  ]  [  -sscale  factor  ]  [  -wwindow ] [ -tsist ] [
     -teiste ] [ -mute ] [ -uiend ]  [  -vvel  ]  [  -ppoly  ]  [
     -fitype ] [ -didec ] [ -rpnramp ] [ -agc ] [ -rms ] [ -M ] [
     -V ] [ -? ]

DESCRIPTION

     davc applies an automatic gain control to trace  data  based
     on average absolute amplitude in a sliding window.

     Davc gets both its data and its parameters from command line
     arguments.   These  arguments specify the input, output, the
     amplitude scale factor , and the operator length in ms.

  Command line arguments
     -Nntap
          Enter the input data set name or file immediately after
          typing  -N;  entering  nothing  specifies a stdin pipe.
          This input put file should include  the  complete  path
          name  if  the  file  resides  in a different directory.
          Example -n/b/vsp/dummy tells the program  to  look  for
          file 'dummy' in directory 'vsp' stored on the 'b' disk.

     -Ootap
          Enter the output data  set  name  or  file  immediately
          after typing -O.  This output file is not required when
          piping the output to another process.  The output  data
          set also requires the full path name (see above).

     -rs irs
          (integer) First record to process (default = 1)

     -re ire
          (integer) Last record to process (default = all)

     -ns ns
          First trace in record to process (default = 1)

     -ne ne
          Last trace in record to process (default = all)

     -sscale factor
          Enter the scale factor that specifies  what  percentage
          of  2047  you  want  the  average  absolute  amplitude.
          (default = 15%)

     -wwindow
          Enter the window in ms to  compute  the  AGC  operator.
          (default = 500ms)

     -tsist
          Enter the scaling start time in ms for the first  input
          record.   No scaling will be done before this time, and
          the gain curve will be  set  to  1  before  this  time.
          Default = 0ms.  This parameter and the one below can be
          used to linearly interpolate the scaling  window  start
          times  from the starting record of the input data (irs)
          to the ending record (ire).

     -tsist
          Enter the scaling start time in ms for the  last  input
          record.   No scaling will be done before this time, and
          the gain curve will be  set  to  1  before  this  time.
          Default = scaling start time for first record.

     -uiend
          Enter the scaling end time in ms.  No scaling  will  be
          done after this time, and the gain curve will be set to
          1 after this time.  Default = end of trace.

     -vvel
          Enter the scaling start time velocity  in  ft  or  m/s.
          This  is used with the ist start and end times above to
          compute the actual trace gain window following a  first
          break or water velocity.  Default = 99999

     -mute
          Enter the command line argument '-mute' to force  scal-
          ing  start  time  to  follow the first break mute line.
          This assumes  a  first  break  mute  has  already  been
          applied  to  the  data  and that there are zeroes above
          this line.   The scaling end time will also follow  any
          off  type mute applied to the data.  This option causes
          the -ts[] -te[] start time option to be ignored.

     -ppoly
          Enter the order of polynomial to fit to the gain curves
          (< 10).  (default = 0 or no polynomial fitting).

     -fitype
          Enter the type of function to  apply.   There  are  two
          choices:   itype  =0  is  an nth order polynomial in X;
          itype =1 is an nth order  polynomial  in  the  gaussian
          function exp(x**2).  Default = 0

     -rms Enter the command line argument '-rms' to use  the  rms
          value  gain  curve  rather  than the average value gain
          curve.


     -agc Enter the command line argument '-agc'  to  output  the
          gain curves only.  These will be in the form of seismic
          traces which have the exact same headers as  the  input
          traces  from  which they were computed.  Application of
          these curves can be done with vmult

     -M   Enter the command line argument '-M' to use the  median
          to compute gain curve; otherwise the average is used.

     -didec
          If median curve is requested enter the window increment
          (ms) for the data in the sliding window used to compute
          median.  The larger this value the faster the  computa-
          tion but the rougher the gain curve.  Default = 100ms

     -rpnramp
          If median curve is requested enter the mute line  ramp.
          If  there  is a mute zone at the start of the data that
          is longer than 1/2 the gain window the median  calcula-
          tion  will  suffer  large transients unless a ramp onto
          the live data is provided.  Default = 48 ms

     Note: use of median calculation can result in ratty  looking
     gain curves which when applied to the data result in "holes"
     in the output.  Use the polynomial curve fitting  option  to
     suppress this tendency, i.e. ipoly=4, itype=0

     Also note that use of long  windows  with  this  option  can
     result in long execution times.

     -V   Enter the command line argument '-V' to get  additional
          printout.

     -?   Enter this (or '-?' if you are running in  c-shell)  to
          get  online  help.   The  program  will terminate after
          printing this.

BUGS

     Unknown

AUTHOR

     Paul Gutowski, TRC x3146

COPYRIGHT

     copyright 2001, Amoco Production Company
               All Rights Reserved
          an affiliate of BP America Inc.