Top Menu

Almost three years ago, while our boat was shrink-wrapped on land, suffering through her last cold winter, I posted about how to calculate the maximum distance that you can see across the water. The formula that I shared in that post can be used when you are searching for a light on land and want to determine how far from the light you will be when it first comes into view. In order to calculate this, you’ll need to take note of the height of the light which should be recorded on the chart or in the List of Lights as well as how high off the water you are. Nice to know but, to tell the truth, we have never actually put this into practice.

The other day though I came across this post on Yachting Magazine which shares a very practical application of what is essentially the same formula. By having previously determined your “height of eye” when standing at your helm, or any other point on your boat, you will automatically know how far away the horizon is.

As an example, when standing at our helm we are approximately 8 feet off the water. Using the formula shared in that post we can calculate that the horizon is approximately 3.3 miles away. This is worth knowing. How high is your “height of eye” when standing at your helm? Don’t guess, get out a tape measure like we did!

For those who are mathematically handicapped, Greg Hannah shared the following on our Facebook Page:

Height (ft) above Water >> Miles to Horizon

  • 6 >> 2.87
  • 7 >> 3.10
  • 8 >> 3.31
  • 9 >> 3.51
  • 10 >> 3.70
  • 11 >> 3.88
  • 12 >> 4.05
  • 13 >> 4.22
  • 14 >> 4.38
  • 15 >> 4.53
  • 16 >> 4.68
  • 17 >> 4.82
  • 18 >> 4.96
  • 19 >> 5.10
  • 20 >> 5.23
  • 21 >> 5.36

The lighthouse on Chacachacare Island is reportedly the second highest in the world.

8 Comments

  1. I did it! I finally did it! I started at the very beginning of your blog and to day at 9:12 am I finally got caught up… This makes me very happy as I can now keep constant with you . Thanks for being so consistent in your writings and in your pursuits. Iwill now look far ward to a daily read…
    Thanx Dan

  2. Thanks for doing the math. I’m keeping this list, it’ll be good to know from everywhere on the boat.

  3. Another practical application all sailors know: stand on the beach (not elevated) and look at the horizon. If it is flat, it’s not too rough out even though the wind seems strong, if there are large waves visible on the horizon and you can see them moving, it’s going to be bumpy. A larger more seaworthy boat? Pick a sighting position that is just a little higher. The point is that you will see the waves that are 1-2 miles distant poking above the horizon ONLY if they are about 1/2 your height.

    Still seeing waves at the horizon from a 2nd story balcony? Roll over and go back to sleep.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

Close