NAME

     zmapvel2sis  - convert gridded zmap or Bfile velocity  func-
     tions into 3D velocity volume

SYNOPSIS

     zmapvel2sis [ -Nntap ] [ -Ootap ] [ -vminvmin ] [  -vmaxvmax
     ]  [  -tmintmin  ]  [  -tmaxtmax  ]  [ -sisi ] [ -vitagi ] [
     -votago ] [ -floorfloor ] [ -ceilceil ] [ -B ] [ -V ] [ -? ]

DESCRIPTION

     zmapvel2sis takes a special zmap or  Bfile  format  file  of
     velocity  functions  on a regular grid corresponding to hor-
     izons and converts this to a 3D velocity volume  where  each
     trace  in  the  volume  has a velocity at every sample.  The
     sparse velocity functions in  the  zmap  file  are  linearly
     interpolated  onto  a equal time grid. The traces comprising
     the volume will have the original line  number  assigned  to
     the  RecNum  record  number  and  the  original trace number
     assigned to the TrcNum trace number.

     Conversions between input average, rms,  and  interval,  and
     output average, rms, and interval velocities are allowed.

     The zmap option is for a scheme due  to  Teresa  Becker  and
     Andrew  Robinson  (OBU)  to convert gridded average velocity
     surfaces (which have been derived for key horizons  using  a
     V0,  K  depth conversion routine in ZNAP+) into a 3D seismic
     trace volume so that it can be imported  into  the  Landmark
     workstation.   Once  in  the  workstation  environment,  the
     interpreter can extract average velocity for any interpreted
     time  horizon  or  time slice in the same way that one would
     extract amplitude for a time horizon.   This  velocity  file
     can be gridded using faults as constraints and multiplied by
     the one-way time grid to get a depth map quickly.   Building
     the input file for zmapvel2sis requires some manipulating to
     get the time-velocity pairs from  multiple  surfaces  refer-
     enced  to  line/trace  locations so cal Andrew or Teresa for
     details.

     The Bfile option is  for  more  general  applications  where
     velocity volume building is required.

     zmapvel2sis gets both its data and its parameters from  com-
     mand  line  arguments.   These  arguments specify the input,
     output, start and end times and velocities, sample interval,
     and verbose printout, if desired.

  Command line arguments
     -N ntap
          Enter the zmap gridded velocity data set name  or  file
          immediately  after typing -N unless the input is from a
          pipe in which case the -N entry must be omitted.   This
          input 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 '/b/vsp'.

     -O otap
          Enter the output velocity data set name or file immedi-
          ately  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).

     -vmin vmin
          Enter the velocity (ft,m/s) at the  minimum  time  (see
          below) of each trace. Default = 4850. Most of the Bfile
          files have a velocity at the surface so be sure to  put
          a -vmin[] that is equal to this. Two minimum velocities
          that are the save don't hurt but if there is a  surface
          velocity  in  each  function of 1500m/s and you default
          the -vmin[] the first velocity in each function will be
          4850ft/s and the seconf will be 1500m/s - bad news.

     -vmax vmax
          Enter the velocity (ft,m/s) at the  maximum  time  (see
          below)  of the trace. Default = maximum velocity in the
          input file.

     -tmin tmin
          Enter the minimum time (ms) of  the  trace.  Default  =
          sample interval

     -tmax tmax
          Enter the maximum time (ms) of  the  trace.  Default  =
          maximum time in the input file.

     -si si
          Enter the sample interval (ms). Default = 4

     -vi tagi
          Enter R for rms velocity input input,  I  for  interval
          velocity  input,  or  A  for  average  velocity  input.
          Default = R

     -vo tago
          Enter R for rms velocity output output, I for  interval
          velocity  output,  or  A  for  average velocity output.
          Default = R

     -floor floor
          Enter the value below which a time or a  velocity  will
          be considered null, i.e. no entry. Default = -0

     -ceil ceil
          Enter the value above which a time or a  velocity  will
          be considered null, i.e. no entry. Default = 1.E10

     -B   Enter the command line argument '-B' for  Bfile  format
          input  velocity  functions,  else sorted zmap functions
          are assumed.

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

     -?   Enter the command line  argument  '-?'  to  get  online
          help.   The program terminates after the help screen is
          printed.

BUGS

     unknown

EXAMPLE

     (1) Using a sorted zmap file called velsort.dat

     zmapvel2sis -Nzmap_file -vmin4850 -vmax10000 -tmax6000 -si4

     | sis2segy -Ovelocity_volume

     This example shows the creation of a  segy  velocity  volume
     ready  for import into an interpretive workstation. The sur-
     face velocity is pinned to 4850ft/s; the bottom velocity  at
     the maximum trace time of 6000ms is pinned to 10000ft/s. The
     sample interval is 4ms.

     (2) Using a BFILE called u4e.stkvbase

     zmapvel2sis -Nu4e.stkvbase -si4 -vmin1500 -Ovels

     where the minimum velocity has been explicitly  input  since
     this  BFILE already has a surface velocity of 1500m/s. If we
     hadn't put it in the first velocity of each  function  would
     have  been  4850ft/s and the second velocity would have been
     1500m/s.

AUTHOR

     Teresa  Becker,   zthb02@orl.amoco.com;   Andrew   Robinson,
     zawr02@orl.amoco.com; Paul Gutowski, zprg03@trc.amoco.com

COPYRIGHT

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