Comparison between line-luminosity estimates based on mapping data from the literature and equivalent estimates using sampling observations. The blue circles represent CO(1−0) luminosities of California, Perseus, and Orion A from Lewis et al. (2022), the red circles the CO(2−1), ¹³CO(2−1), and C¹⁸O(2−1) luminosities of Orion A from from Nishimura et al. (2015), the green circles the CO(1−0) and¹³ CO(1−0) luminosities of Perseus from Ridge et al. (2006), and the yellow circle the HCN(1−0) luminosity of Perseus from Dame & Lada (2023). The dashed line marks the locus of equal estimates, and the dotted lines correspond to differences of 50%. All estimates assume the cloud distances given in Sect. 1.