Owing to the frequency switching mode used for this survey, its velocity range is relatively small, -22 to 30 km/s. This range is
adequate to cover essentially all the CO emission at b < -5, but not so at higher latitudes closer to the Galactic plane. In
the range b = -5 to -2 it is better to use one of the second quadrant surveys (DHT17 or DHT18), which have wider velocity
coverage. The interpolated cube is recommended as it fills in a few missing spectra at random locations as well as the
1/4° sampling along the bottom.