Ahoy, there!
I know this wont be of interest to all you Pirate Legends out there; because you all doubtless know the Sea of Thieves like the backs of your craggy, weather-beaten hands.
But for the rest of you: All of you that find yourself looking a Gold Hoarders "X marks the spot" treasure map, and then dragging the ship's table map hither and yon, trying to find which island you have a map for, I have a tool for you!
If you have an unfamiliar treasure map, simply go to http://www.surveyorpete.fun/Tools/WhatIsland, answer a few basic questions about the general appearance of the island you are looking for, and get presented with a handy list of likely candidates. Beneath each map thumbnail, there is the name of the island, and its (new) map reference!
If you disagree with some of my categorisations of the appearance of the island, let me know below. Note, however, some of the categorisations are deliberately "fuzzy" to give people the best chance of getting a match. For example, Lagoon of Whispers may be presented regardless of which "dominant terrain" you suggest: Sand or Rock or Vegetation. This is because that island has all three in equal measure.
-- Providing yet another advantage to PC players :-)

