Deciview is a unit of visibility. It is proportional to the logarithm of the atmospheric coefficient. The atmospheric coefficient in this case is the ratio of a measured physical quantity to a reference value. This creates a scale that is approximately linear with respect to changes as perceived by human senses
Source: Malm, William C. 1999. Introduction to visibility. Cooperative Institute for Research in the Atmosphere. NPS Visibility Program, Colorado State University, Fort Collins, CO: 79 p. As cited in: Hardy, Colin C., Ottmar, Roger D., Peterson, Janice L., Core, John E., and Seamon, Paula. 2001. Smoke Management Guide for Prescribed and Wildland Fire 2001 Edition. Produced by the National Wildfire coordinating Group Fire Use Working Team.
IMRPOVE Newsletter. 1993 Improve monitoring update. Vol. 2 No.1 April 1993. Pgs 1-4.