NavList:

Thanks, Gary. That's very useful. May I ask, is this a Google Maps overlay that you created?

In the image that you included, there's a "pin" marking a location just to the west of my phantom seamount as "Reef reported in 1954 per H.O. 126". This is probably connected in some way with the underlying data source that generated this non-existent seamount but it seems that it must be a rather indirect connection. The rectangular shallow area is very large (about a hundred square miles) and the "reef reported" location is actually outside of the rectangle.

Of course, phantom "reefs" have been a problem in ocean charts since the earliest times. A deepsea eruption, a decomposing whale, or even a huge shoal of fish under attack by a bunch of sharks can create the illusion of waves breaking over a reef in mid-ocean. Historically (though very unlikely as late as 1954), many phantom reefs were simply errors in longitude. A real reef at some latitude and longitude would often be double-plotted at nearly the same latitude but a degree or more to the east or west.

By the way, the same plot that you posted indicates another "uncharted reef" about sixty miles south. This one is at least consistent with the gravity deflection map. There is definitely an extension of that small island group visible in the gravity data extending it further to the east so there could easily be a reef at some relatively shallow depth.

Robin, the misplaced label for that island in Boston Harbor is a more common, and I would say completely understandable, issue for Google Maps, since it's a cultural marker. The island is in the right place in all the data layers and in all versions of the basic Google mapping product that I looked at. The label is in a (more) correct location in other versions of the product. The managers of Google Maps allow a certain amount of "crowd-sourcing" in map labels. Occasionally users will move a label to an incorrect location. Then months later it will shift to some other spot. But that's cultural, not physical data.

-FER

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