NAME

     xytrp  - interpolate an X-Y grid of data (in USP format)

SYNOPSIS

     xytrp [ -Nntap ] [ -Ootap ]  [  -dxidxi  ]  [  -dxodxo  ]  [
     -dyidyi  ] [ -dyodyo ] [ -oxioxi ] [ -oyioyi ] [ -oxooxo ] [
     -oyooyo ] [ -B ] [ -I ] [ -Z ] [ -vel ] [ -V ] [ -? ]

DESCRIPTION

     xytrp takes X-Y gridded data, e.g. time slices, and interpo-
     lates  the  amplitudes  onto  a new grid. A grid of data (an
     input record) is defined in terms of lines (for  each  trace
     all samples) which is aligned with the X-axis and crosslines
     (for each sample all traces) which is aligned  with  the  Y-
     axis.  If you display a time slice using xsd then the X-axis
     is vertical (samples) and the Y-axis is horizontal (traces).
     The cell dimensions are given by dy (spacing between traces)
     and dx (spacing between samples). The number of output  sam-
     ples  and  traces  is  computed  by multipling the number of
     input samples (or traces) by the ratio of the input to  out-
     put cell dimensions then subtracting 1 (the outer boundaries
     of the survey are fixed  and  new  points  are  interpolated
     between the old).

     The default interpolation mode is a 2D sinc function but the
     user can specify a slightly cruder but faster bilinear mode.
     Also the reciprocal sample values can be interpolated rather
     than the sample values.

     xytrp gets both its data and  its  parameters  from  command
     line  arguments.  These arguments specify the input, output,
     the input and output cell dimensions, and verbose  printout,
     if desired.

  Command line arguments
     -N ntap
          Enter the input 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 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).

     -dxi dxi
          Enter the X-dimension of an input cell (spacing between
          samples). No default.

     -dxo dxo
          Enter  the  X-dimension  of  an  output  cell  (spacing
          between samples). No default.

     -dyi dyi
          Enter the Y-dimension of an input cell (spacing between
          traces). No default.

     -dyo dyo
          Enter  the  Y-dimension  of  an  output  cell  (spacing
          between traces). No default.

     -oxi oxi
          Enter the input X origin. Default = 0.0

     -oyi oyi
          Enter the input Y origin. Default = 0.0

     -oxo oxo
          Enter the output X origin. Default = 0.0

     -oyo oyo
          Enter the output Y origin. Default = 0.0

     -B   Enter the command line argument '-B' to  use  the  bil-
          inear  interpolator (faster) rather than the sinc func-
          tion. This type of interpolator works better for nonse-
          ismic  data sets line velocities, Qs, gravity/mag maps,
          etc.

     -I   Enter the command line argument '-I' to interpolate the
          reciprocal  sample  values.  Useful  for  interpolating
          velocity and Q fields.

     -Z   Enter the command line argument '-Z' to  zero  out  the
          edges of the interpolated field.

     -vel Enter the command line argument '-vel'  to  interpolate
          nonseismic  data  sets like velocities, Qs, gravity/mag
          maps, etc"

     -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.

EXAMPLE

     To run the interpolation on time slice data we need to slice
     the original volume:

     ttds3d -Nindata -NDtxy -ODxyt -Ttmp -Otidata

     where indata is the stacked 3D  volume  and  tidata  is  the
     resulting  time  slice  data  and where we have used the MBS
     data transpose program ttds3d to do the  slicing  (we  could
     have  also  used  the faster USP slicer fqdslice). Now we do
     the interpolation:

     fkkstrip -Ntidata -l3 -pass |\
     xytrp -dxi200 -dyi200 -dxo100 -dyo100 -Oodata -B

     where we have gone from a cell size of  200x200  to  a  cell
     size  of  100x100.  We  have pre-filtered the 2D slices with
     fkkstrip to minimize the effects of aliasing. We could  also
     have used fftxy|polymute|fftxy -R in place of fkkstrip where
     the polymute is less intrusive than the 3x3 bessel filter of
     fkkstrip.

     Consider the flow

     ttds3d -Nindata -NDtxy -ODxyt -Ttmp1 -M32 |\
     xytrp  -dxi200 -dyi200 -dxo100 -dyo100 |\
     ttds3d -NDxyt -ODtxy -Ttmp2 -M32 |\
     editt  -U -t1 -u1 |\
     li_di  -ildm100 -cldm100 -x10 -y10 -x215000 -y20 \
            -x315000 -y315000 -x40 -y415000 -stk -BRI -Oodata

     which shows a complete run from  an  input  stacked  volume,
     through  slicing, interpolation using the sinc function, and
     then unslicing. The editt renumbers  the  record  and  trace
     numbers  (RecNum  &  TrcNum)  starting  from the appropriate
     values and the li_di recomputes the bin center XYs based  on
     these numbers and the input survey extents.

BUGS

     does not internally reindex the LIs and DIs; nor does it put
     in the new bin center XYs.

SEE ALSO

     ttds3d, qdslice

AUTHOR

     Paul Gutowski (socon 422-3146)

COPYRIGHT

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