visual - Puzzle Hunt 01: A cliched treasure map

This is my first puzzle, but strongly influenced in style by the type of puzzles you see monthly at Puzzled Pint. If you are fortunate enough to live in a city where they are hosted, I would really recommend going. Depending on how this one goes, it is planned to be the first of a series along the (deliberately clichéd) theme of a treasure hunt.

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This story begins like any good treasure island story, with a cliché!

Your widowered father is aging, and the family have decided to move him to a retirement home so he can get the care he needs. He has been living by himself for the past decade and has accumulated a lot of various items - to be brutally honest, mostly junk. Being the most limber you volunteer to clean out the attic. While scrambling around - being carefull not to put your foot through the ceiling - you come across an old backpack which contains a collection of paraphernalia one might expect to see for an old-timey exploerer, such as a gas lamp, rope, hard hat, and a scrap of paper. The paper catches your eye. You pocket it and head down for an explanation.

"What's this?" you ask.

"That's an old treasure map." He says, somewhat matter-of-factly.

"Go on..."

"It is back from when I was in the navy. We found this map, found the island too. Scoured it as best we could, but only had a couple of weeks we could spare. It was abandoned, but we certainly weren't the first there. Rumour was that a treasure of some fantastic nature was hidden somewhere on it. I was putting together a few things to go back and search for it, but that is when your mother passed and my priorities shifted a bit. Then I guess I just lost the enthusiasm."

You examine the map closely. It contains a coded message which might give some clue as to location or nature of the treasure. Or it might be meaningless twaddle, but it is a good a place as any to start.

Question: What is the message?

The handwriting on the map is not great, so a transcription of the coded phrase is given below if required.

B BBDAABBBCC CDDDAAA CCADDC

Answer

The message is:

X MARKS THE SPOT

The way to reveal it:

Each subset of letters leads to a location. A single A is A1, AA is A2, etc. Each respective square on the map refers to a letter: A1 is P(hilips), A2 is R (Arr!), A3 is E (Echo) and so on.