On the possibility of determining the distance to the Galactic center   from the geometry of spiral arm segments
  A new approach to determining the solar galactocentric distance, $R_0$, from the geometry of spiral-arm segments is proposed. Geometric aspects of the problem are analyzed and a simplified three-point method for estimating $R_0$ from objects in a spiral segment is developed in order to test the proposed approach. An estimate of $R_0 = 8.44 \pm 0.45$ kpc is obtained by applying the method to masers with measured trigonometric parallaxes, and statistical properties of the $R_0$ estimation from spiral segments are analyzed. 
I.I. Nikiforov, A.V. Veselova
astro-ph.GA