Face-on view of the number of components with distance results that cause an absolute v_LSR deviation of more than 10 km s⁻¹ compared to the Galactic rotation curve model for the BDC results obtained with (left) and without (right) the spiral arm prior. The values are binned in 10 × 10 pc cells and the values were summed up along the z_gal axis. The position of the Sun and Galactic centre are indicated by the Sun symbol and black dot, respectively. When displayed in Adobe Acrobat, it is possible to show the spiral arm positions, hide the curves of constant projected v_LSR, and show the grid.