Program sfspiralsort | Sort microseismic surface array recording traces with a given epicenter along a spiral shape R = r0 + d(a-a0). 
[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
[DIRECTORY]
user/yunzhi
