  The sensitivity and versatility of SKA will provide microarcsec astrometric
precision and high quality milliarcsec-resolution images by simultaneously
detecting calibrator sources near the target source. To reach these goals, we
suggest that the long-baseline component of SKA contains at least 25% of the
total collecting area in a region between 1000 to 5000 km from the core SKA. We
also suggest a minimum of 60 elements in the long-baseline component of SKA to
provide the necessary (u-v) coverage. For simultaneous all-sky observations,
which provide absolute astrometric and geodetic parameters, we suggest using
ten independent subarrays each composed of at least six long-baseline elements
correlated with the core SKA. We discuss many anticipated SKA long-baseline
astrometric experiments: determination of distance, proper motion and orbital
motion of thousands of stellar objects; planetary motion detections; mass
determination of degenerate stars using their kinetics; calibration of the
universal distance scale from 10 pc to 10 Mpc; the core and inner-jet
interactions of AGN. With an increase by a factor of 10 in absolute astrometric
accuracy using simultaneous all sky observations, the fundamental quasar
reference frame can be defined to <10 microarcsec and tied to the solar-system
dynamic frame to this accuracy. Parameters associated with the earth rotation
and orientation, nutation, and geophysical parameters, can be accurately
monitored. Tests of fundamental physics include: solar and Jovian deflection
experiments, the sky frame accuracy needed to interpret the gravity
wave/pulsar-timing experiment, accurate monitoring of spacecraft orbits which
impacts solar system dynamics.
