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We applied the currently most comprehensive version of thestatistical-parallax technique to derive kinematical parameters of the masersample with 136 sources. Our kinematic model comprises the overall rotation ofthe Galactic disk and the spiral density-wave effects. We take into account thevariation of radial velocity dispersion with Galactocentric distance. The bestdescription of the velocity field is provided by the model with constant radialand vertical velocity dispersions, $(\sigma U0, \sigma W0) \approx (9.4 \pm0.9~, 5.9 \pm 0.8)~ km/s$. We compute flat Galactic rotation curve over theGalactocentric distance interval from 3 to 15 kpc and find the local circularrotation velocity to be $ V_0 \approx (235-238)$~ km/s $\pm 7$~ km/s. We alsodetermine the parameters of the four-armed spiral pattern (pitch angle $i\approx (-10.4 \pm 0.3)^\circ$ and the phase of the Sun $\chi_0 \approx (125\pm 10) ^\circ$). The radial and tangential spiral perturbations are about $f_R\approx (-6.9 \pm 1.4)$~km/s, $f_\Theta \approx (+2.8 \pm 1.0$) ~km/s. Thekinematic data yield a solar Galactocentric distance of $R_0 \approx (8.24 \pm0.12)~kpc$. Based on rotation curve parameters and the asymmetric drift weInfer the exponential disk scale $H_D \approx (2.7 \pm 0.2)$ ~kpc underassumption of marginal stability of the intermediate-age disk, and finally weestimate the minimum local surface disk density, $\Sigma (R_0) > (26 \pm 3) ~M_\odot pc^{-2}$.

Galactic masers: kinematics, spiral structure and the disk dynamic state