Sunday, March 29, 2009

How Tall?

Isle au Haut, by Peter M. Mason,
from Maine Lighthouses Illustrated Map & Guide

How tall is a lighthouse?

You're probably thinking: Well, duh...It's the distance from the bottom to the top.

That's what I thought, till I decided it would be a good idea--easy too!--to include the stats for each lighthouse in its description on the back of our new Maine Lighthouses map. Then I discovered that there are probably as many ways to measure a lighthouse as there are to skin a cat.

For example, take the Isle au Haut light. As you can see in the illustration above, the building is composed of a granite block base, a white-painted brick cylinder and a black lantern room with deck.

According to this website, the tower height is 40 feet. Does that mean:
  1. the entire structure, from block base to pointy top?
  2. the block base & brick cylinder?
  3. just the brick cylinder?
  4. the brick cylinder to pointy top?
And that's just one of the 79 lighthouses detailed in the guide.

So how do you know whether lighthouse heights are measured consistently?

According to our researcher, Maine lighthouse expert Peter Dow Bachelder, you don't. You go by guess and by God, then get over it.

So I did.


  1. I can't resist the opportunity to be first commenter. As a former cartographer who just got his first book deal, I'm surprised and pleased to find someone else with the same two professional interests. Your maps look great; the watercolors are splendid. I'll do my part getting the word out.

  2. Thanks, Stephen, and congrats on your book deal! Honored to have you be the first here.