SUMIGPS - MIGration by Phase Shift with turning rays

sumigps <stdin >stdout [optional parms]

Required Parameters:
None

Optional Parameters:
dt=from header(dt) or .004 time sampling interval
dx=from header(d2) or 1.0 distance between sucessive cdp's
ffil=0,0,0.5/dt,0.5/dt trapezoidal window of frequencies to migrate
tmig=0.0 times corresponding to interval velocities in vmig
vmig=1500.0 interval velocities corresponding to times in tmig
vfile= binary (non-ascii) file containing velocities v(t)
nxpad=0 number of cdps to pad with zeros before FFT
ltaper=0 length of linear taper for left and right edges",
verbose=0 =1 for diagnostic print


tmpdir= if non-empty, use the value as a directory path
prefix for storing temporary files; else if the
the CWP_TMPDIR environment variable is set use
its value for the path; else use tmpfile()

Notes:
Input traces must be sorted by either increasing or decreasing cdp.

The tmig and vmig arrays specify an interval velocity function of time.
Linear interpolation and constant extrapolation is used to determine
interval velocities at times not specified. Values specified in tmig
must increase monotonically.

Alternatively, interval velocities may be stored in a binary file
containing one velocity for every time sample. If vfile is specified,
then the tmig and vmig arrays are ignored.

The time of first sample is assumed to be zero, regardless of the value
of the trace header field delrt.

Credits:
CWP: Dave Hale (originally called supsmig.c)

Trace header fields accessed: ns, dt, d2