SUKFILTER - radially symmetric K-domain, sin^2-tapered, polygonal filter

sukfilter <infile >outfile [optional parameters]

Optional parameters:
k=val1,val2,... array of K filter wavenumbers
amps=a1,a2,... array of K filter amplitudes
d1=tr.d1 or 1.0 sampling interval in first (fast) dimension
d2=tr.d1 or 1.0 sampling interval in second (slow) dimension

Defaults:
k=.10*(nyq),.15*(nyq),.45*(nyq),.50*(nyq)
amps=0.,1.,...,1.,0. trapezoid-like bandpass filter

The nyquist wavenumbers, nyq=sqrt(nyq1^2 + nyq2^2) is computed
internally.

Notes:
The filter is assumed to be symmetric, to yield real output.

Because the data are assumed to be purely spatial (i.e. non-seismic),
the data are assumed to have trace id (30), corresponding to (z,x) data

The relation: w = 2 pi F is well known for frequency, but there
doesn't seem to be a commonly used letter corresponding to F for the
spatial conjugate transform variables. We use K1 and K2 for this.
More specifically we assume a phase:
-i(k1 x1 + k2 x2) = -2 pi i(K1 x1 + K2 x2).
and K1, K2 define our respective wavenumbers.


Credits:
CWP: John Stockwell, June 1997.

Trace header fields accessed: ns, d1, d2