Correlation between Type 1 and Type 2 CO maps at 115 GHz (left column) and 230 GHz (right column) in the Taurus (top), Orion (middle) and Polaris (bottom) molecular clouds. The best linear fits (orange solid line) have been computed between 2 and 15 K km s^-1 at 115 GHz and between 1 and 15 K km s^-1 at 230 GHz, where bulk of the data lie and avoiding the noise around zero. The best-fit slopes and uncertainties are: a)1.12 ± 0.03; b) 1.14 ± 0.01; c) 1.10 ± 0.04; d) 1.07 ± 0.01; e) 1.07 ± 0.06; and f) 1.17 ± 0.04. The intercepts are compatible with zero within error bars. The orange dot-dashed lines in the bottom panels correspond to the recalibration uncertainty due to the contribution of the J = 3 → 2 line in the Type 2 J = 2 → 1 product. See text for detail.