# Horizon distance

From AMS Glossary

## horizon distance

The distance, at any given azimuth, to the point on the earth's surface constituting the horizon for some specified observer.

In the particularly simple case of an observer at sea, the horizon distance which holds to a good degree of approximation as long as both

*s*in miles corresponding to an observer whose eye is at a height*h*feet above sea level, is given by the relation*s*and*h*are small compared to the earth's radius.