Subject: Re: Distance to the horizon
Date: Fri, 06 Aug 2000 12:03:37 -0700
From: David L. Arnett

Tom and Alex,

Reading your question reminds me of my days as a sailor. We had a slightly easier formula (though not quite as accurate) that worked well for approximating distances using the range of heights you are talking about. I have modified it to take a height input in feet, and give an answer in (5,280') miles:

distance = 1.29*sqrt(height)

This is the distance to the horizon from a given height. If you want to know about seeing another object, just do the calculation twice and add the numbers.

For a 5'9" man and a 200' island, this would give:

1.29*sqrt(5.75)+1.29*sqrt(200) = 21.3 miles

It's not as exact as the Pythagorean Theorem, but it gives an (easier?) answer which can be used for practical purposes such as navigation. Just don't forget to add the height of whatever your standing on!

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