Synopsis
		sfpick2 < scn.rsf > pik.rsf slice=0 vel0=o2 rect1=1 rect2=1 niter=100 an=1. gate=3

Parameters
		float an=1. axes anisotropy   int gate=3 picking gate   int niter=100 number of iterations   int rect1=1 smoothing radius on the first axis   int rect2=1 smoothing radius on the second axis   int slice=0 if only one kind of slicing (1: inline, 2: time)   float vel0=o2 surface velocity