PROCESS UFILTR


Document Date: 11 November 1982

PROCESS UFILTR applies user given filter points to every seismic trace.
The filtering is done as convolution in the time domain. The user may 
specify the time origin of the filter by specifying the amount of shift
to apply after convolution.  Zeroes are inserted before and after the
data trace so that full convolution is performed without program buffer
edge effects.

One use of process ufiltr is in applying a single compensation filter
to all data.  Another use is in applying a Hilbert transform or first
derivative filter (1,-1).

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

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

FILPTS - A list of filter points, each value separated from the other
         by a blank.  The points may be given on as many lines as
         necessary. When the values are given in an exponential format,
         positive exponents must have a + rather than a blank.
         Required. e.g. filpts .5 .5

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

LNO    - The last shot (rp) number to apply the filter to.  LNO must be
         larger than FNO in each list and must increase list to list.
         Default=fno

NSHIFT - The number of samples to shift the data after convolution.  A
         negative shift moves the data to the left and NSHIFT data 
         values are dropped from the beginning.  A positive shift moves
         the data to the right and NSHIFT zeroes are inserted at the
         beginning of data.  A zero phase filter should have a shift of
         -nfpts/2.
         Preset=0. e.g. nshift -15

END    - Terminates each parameter list.


Written and copyrighted (c) by:
Paul Henkart, Scripps Institution of Oceanography, November 1982 
ALL RIGHTS RESERVED.