# Visual-range formula

From AMS Glossary

## visual-range formula

The formula for the daytime visual range where there is a contrast

*V*,*C*between the horizon target and its background viewed through an atmosphere of extinction coefficient σ by an observer whose momentary threshold contrast is ε.In practice, an important application of this formula is to the case of a black target (for which In calculations of the meteorological range, the threshold contrast is also assigned a constant value.

*C*= 1); hence