Synopsis
		sfspiralsort < in.rsf x=x_file.rsf y=y_file.rsf > out.rsf dist=dist_file.rsf theta=theta_file.rsf epi_x= epi_y= radius0=1.0 angle0=0.0 dr=

Parameters
		float angle0=0.0 Starting angle of spiral.   file dist= auxiliary output file name   float dr= Spiral interval parameter.   float epi_x= referenced epicenter coordinate x.   float epi_y= referenced epicenter coordinate y.   float radius0=1.0 Starting radius of spiral.   file theta= auxiliary output file name   file x= auxiliary input file name   file y= auxiliary input file name