Expert: Ned Dolan - 10/28/2006

Question
Hello Mr. Dolan,

Would you happen to know the basic formula to find the distance seen per elevation?

Thanks in advance!

Rob.

Answer
Hi Rob, no I don't, but the following is from "Piloting, Seamanship and small boat handling"

The distance a light can be seen from a height of 15 feet above the surface is decreased by 1.8 miles if the height is lowered by 10 feet and is decreased by .8 miles if decreased by 5 feet. It is increased by .7 miles if the height is increased by 5 feet.

You may get more info at the following web site.
http://cnx.org/content/m0538/latest/

Hope this helps.  Ned