Readme for spiral_m2_147.dat 

Data are positions for two arms. The first four columns are R,phi,X,Y of arm1, followed by the same for arm 2. (R,phi) are galactocentric with phi in radians, (X,Y) are heliocentric. Length units are R_sun = 1. So, scale to your adopted Rsun by multiplying the R,X and Y columns by Rsun. 

Data generated by logspiral.pro with a pitch angle of 14.7 degrees,.. 