What is a lighthouse?

With today's automated navigation aids, the definition of a lighthouse has blurred a bit. GPS Point of Interest (POI) files include several "lighthouses" that are not really lighthouses, but rather automated pier lights or navigation lights. (See my post dated November 18, 2008.) Even some of the older "lighthouses" fall into this distinction. For instance, would you consider the Calumet Harbor Light in Indiana to be a lighthouse? Calumet Harbor Light Photo. Would you want to spend all day driving around trying to find this "lighthouse" only to find out it can barely be called a structure, let alone a "lighthouse"? Sure it "houses" a light, but let's really stop and think about this for a moment.

Accroding to Merriam-Webster, a "lighthouse" is defined as "a structure with a powerful light for guiding sailors."(1) What kind of definition is that? A "lighthouse" was suppose to designate an actual residence that provided a home for the lighthouse keeper. The house and light did not have to be part of the same structure, but they had to be relatively close to each other. This makes even some skeleton tower lighthouses suspect to the definition of a "lighthouse".

For me, lights like Calumet Harbor, Indiana Harbor (Photo), and Bluffington Harbor (Photo) are hard to define as lighthouses. (Sorry, Indiana - I am not picking on you. You'll always be my home, no matter where I go).

So, for my readers, what actually does consitute a "lighthouse"? In your opinion, how would you define a "lighthouse"?

Notes:
1. Merriam-Webster Dictionary. Merriam-Webster: Springfield. 1997. p.430.