Synopsis
		sfshoot2 < vel.rsf > out.rsf shotfile=shots.rsf vel=y order=4 nt=nx*nz nr=1 r0=x0 dr=dx tol=0.01

Parameters
		float dr=dx receiver increment   int nr=1 number of recievers   int nt=nx*nz Maximum number of time steps   int order=4 Interpolation order   float r0=x0 first receiver   string shotfile= file with shot locations (auxiliary input file name)   float tol=0.01 Shooting tolerance (in degrees)   bool vel=y [y/n] If y, the input is velocity; if n, slowness