Synopsis
		sftahfilter < in.rsf > out.rsf filter_file=filter_file.rsf filter= verbose=1 filt_indx_t0=0

tah is the abbreviation of Trace And Header. Madagascar programs
that begin with sftah are a designed to:
1- read trace and headers from separate rsf files and write them to
standard output (ie sftahread)
2- filter programs that read and write standard input/output and
process the tah data (eg sftahnmo, sftahstack)
3- read tah data from standard input and write separate rsf files for
the trace and headers data (ie sftahwrite)

These programs allow Seismic Unix (su) like processing in Madagascar.
Some programs have su like names.

Some programs in this suite are sftahread, sftahgethw, ftahhdrmath,
and sftahwrite.

The sftahfilter program is designed to apply a filter. Trace and
header data (tah) are read from from standard input (usually a pipe).
A filter is read from the command line or from a file. If the filter
is read from a file, it can be a single filter, or one filter for each
trace. Future enhancements would be to use trace headers to define
a location in the filter file and read that filter or even interpolate
a filter. That would support shot or receiver dependent filter for
surface consistant decon. Another enhancement would be to add
frequency domain bandpass filters.

EXAMPLE:

sftahsort input=shots-receivers-23900_headfix.rsf \
sort="xline:600,601 offset" \
| sftahfilter filterfile=dephase.rsf \
| sftahmakeskey pkey=xline skey=cdpt \
| sftahwrite \
verbose=1 \
label2=cdpt o2=1 n2=100 d2=1 \
label3=xline o3=600 n3=1 d3=1 \
output=dephasecmps.rsf \
>/dev/null

sfgrey
In this example a deterministic dephase filter is applied to a prestack
datafile.

The shot organized prestack data, shots-receivers-23900_headfix.rsf
are read in xline offset order by sftahsort program. The headers are
in the file shots-receivers-23900_headfix_hdr.rsf, the headers
parameter default. The headers are merged with the trace amplitudes
and the tah data sent down the pipe to apply a filter.

The sftahfilter program applies a filter contained in the dephase.rsf
file.

The program sftahmakeskey is used to create a secondary key used
in the following sftahwrite to define the location to wrte the trace
in the output file. Sftahmakeskey makes a secondary key (skey=cdpt)
the count the traces starting in the a primary key gather (pkey=xline).
The input traces gathered by xline by sftahsort. Sftahmakeskey sets
cdpt to 1 when the trace has a new xline. If the trace has the same
xline as the previous trace cdpt is incremented

sftahwrite writes the trace data to dephasecmp.rsf and the headers
are written to the file dephasecmp_hdr.rsf. The order of the data in the
file is defined by the cdpt and xline trace headers, so the data order
is (time,cmpt,xline). Finally, the output volume is displayed using
sfgrey.

Parameters
		int filt_indx_t0=0 indx to time 0 in the filter. Must be in the range [0,numfilter)   floats filter= A list of floats that is the filter to convolve on the input traces. [numfilter]   string filter_file= name of the rsf file containing the filter(s) (auxiliary input file name)   int verbose=1 flag to control amount of print 0 terse, 1 informative, 2 chatty, 3 debug

Used In
		DATA          seam-phase1-2d/filter