Maser Astrometry with VLBI and the SKA
  We discuss the unique opportunities for maser astrometry with the inclusion
of the Square Kilometre Array (SKA) in Very Long Baseline Interferometry (VLBI)
networks. The first phase of the SKA will enable observations of hydroxyl and
methanol masers, positioning the latter to an accuracy of 5 microarcseconds,
and the second phase may allow water maser observations. These observations
will provide trigonometric distances with errors as small as 1%. The unrivalled
sensitivity of the SKA will enable large-scale surveys and, through joint
operations, will turn any VLBI network into a fast astrometry device. Both
evolved stars and high mass star formation regions will be accessible
throughout the (Southern) Milky Way, completing our understanding of the
content, dynamics and history of our Galaxy. Maser velocities and proper
motions will be measurable in the Local Group of galaxies and beyond, providing
new insights into their kinematics and evolution.
