  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.
