2003ApJ...587..701F

The Very Large Array was used to observe H I absorption against 20 compact and ultracompact H II (UC H II) regions, thereby resolving the kinematic distance ambiguity to these sources. Combining these results with other sources whose distances were resolved through H I absorption, the half-width at half-maximum of the distribution of source height above and below the Galactic plane is found to be 35±2 pc within the solar circle. The vertical height distribution is used to investigate the predictive accuracy of the Galactic latitude in resolving the kinematic distance ambiguity to UC H II regions without the need for H I observations. For a large difference between far and near kinematic distances, high accuracy can be achieved by choosing the kinematic distance closer to 1.84|b|^–1 kpc, where b is the Galactic latitude in degrees.