The Bar and Spiral Structure Legacy (BeSSeL) Survey: Mapping the Milky
  Way with VLBI Astrometry
  Astrometric Very Long Baseline Interferometry (VLBI) observations of maser
sources in the Milky Way are used to map the spiral structure of our Galaxy and
to determine fundamental parameters such as the rotation velocity ($\Theta_0$)
and curve and the distance to the Galactic center (R$_0$). Here, we present an
update on our first results, implementing a recent change in the knowledge
about the Solar motion. It seems unavoidable that the IAU recommended values
for R$_0$ and $\Theta_0$ need a substantial revision. In particular the
combination of 8.5 kpc and 220 \kms\, can be ruled out with high confidence.
Combining the maser data with the distance to the Galactic center from stellar
orbits and the proper motion of Sgr\,A* gives best values of R$_0$ = 8.3 $\pm$
0.23 kpc and $\Theta_0$ = 239 or 246 $\pm$ 7 \kms, for Solar motions of V$_
\odot$ = 12.23 and 5.25 \kms, respectively. Finally, we give an outlook to
future observations in the Bar and Spiral Structure Legacy (BeSSeL) Survey.
