Ground-Based Astrometry 2010-2020
  We discuss the opportunities for astronomical discovery via ground-based
astrometry carried out in the United States during the 2010-2020 decade. We
describe imminent scientific breakthroughs that can be achieved at both classic
astrometric scales -- narrow angle astrometry done by individual groups and
large A*Omega astrometry carried out by consortia. The two most compelling
questions to be addressed are (1) What is the composition of the stellar and
substellar population near the Sun? and (2) What are the shape, size, and mass
of the Milky Way? We provide a short list of five recommendations that we
believe will allow us to take best advantage of the intellectual and financial
investments made for what some have called "The Decade of Astrometry." The most
important recommendation is to provide the educational foundation required so
that a new generation of astrometrists can make best use of the rich datasets
that will arrive in the coming decade.
