  We present a 0.16% precise and 0.27% accurate determination of R0, the
distance to the Galactic Center. Our measurement uses the star S2 on its
16-year orbit around the massive black hole Sgr A* that we followed
astrometrically and spectroscopically for 27 years. Since 2017, we added
near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a
direct measurement of the separation vector between S2 and Sgr A* with an
accuracy as good as 20 micro-arcsec in the best cases. S2 passed the pericenter
of its highly eccentric orbit in May 2018, and we followed the passage with
dense sampling throughout the year. Together with our spectroscopy, in the best
cases with an error of 7 km/s, this yields a geometric distance estimate: R0 =
8178 +- 13(stat.) +- 22(sys.) pc. This work updates our previous publication in
which we reported the first detection of the gravitational redshift in the S2
data. The redshift term is now detected with a significance level of 20 sigma
with f_redshift = 1.04 +- 0.05.
