Abstract
We are testing a method to solve for the distances of a sample of ultra-compact (UC) HII regions with IRAS colors and CS(J=2-1) detection. The ambiguity in their kinematical distances is solved using Monte-Carlo simulations. We simulated heliocentric longitude-Radius (l-R) on Galactic plane distributions, and their respective longitude-Velocity_{LSR} (l-V_{LSR}) projections using synthetic associated molecular clouds. The best Galactic distribution is selected by comparison with observed CO maps. Preliminary results for the Galactic quadrant IV are presented.
