The Norma spiral arm: large-scale pitch angle
  In the inner Galaxy, we statistically find the mean pitch angle of the
recently mapped Norma arm in two galactic quadrants (observed tangentially at
galactic longitudes near l=328 degrees and near l=20 degrees), using the
twin-tangent method, and obtain -13.7 +/-1.4 degrees. We compared with other
measurements in the literature.
  Also, using the latest published data on pitch angle and the latest published
data on the radial starting point of the four arms (RGal = 2.2 kpc) in each
galactic quadrant, a revised velocity plot of the Norma spiral arm is made,
along with other spiral arms in the Milky Way, in each Galactic quadrant.
