Visual range

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visual range

(Or daytime visual range.) The distance, under daylight conditions, at which the apparent contrast between a specified type of target and its background becomes just equal to the threshold contrast of an observer; to be distinguished from the night visual range.

The visual range is a function of the atmospheric extinction coefficient, the albedo and visual angle of the target, and the observer's threshold contrast at the moment of observation. Only in the so-called meteorological range does one have a visibility figure dependent only upon the extinction coefficient.
See visual-range formula;
compare visibility.

Middleton, W. E. K. 1952. Vision through the Atmosphere. 104–122.

Johnson, J. C. 1954. Physical Meteorology. 79–90.

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