  There are many fundamental aspects of Galactic structure and evolution which
can be studied best or exclusively with high quality three dimensional
kinematics. Amongst these we note as examples determination of the orientation
of the stellar velocity ellipsoid, and the detection of structure in
velocity-position phase space. The first of these is the primary limitation at
present to reliable and accurate measurement of the Galactic gravitational
potential. The second is a critical test of current standard models of Galactic
formation and detection of structure in velocity-position phase space. The
first of these is the primary limitation at present to reliable and accurate
measurement of the Galactic gravitational potential. The second is a critical
test of current standard models of Galactic formation and evolution.
