I think they apply all of those things, redshift, blueshift, exc...to arrive at a more precise analysis. But the method I hear of the most is we use the distance to a globular cluster to calibrate the distances to a number of other globular clusters. By determining the center of their distribution, we get an estimate of the distance to the center of the Galaxy.
http://heasarc.gsfc.nasa.gov/docs/co...yway_info.html http://www.astro.washington.edu/labs...er_galaxy.html http://fuse.pha.jhu.edu/outreach/kit1/trig.html
Hope that helps.
