Chart Essay


A NOAA chart of Spectacle before the Big Dig fill. The round drumlins north and south and the narrow middle gave the island its "spectacle" shape and name. Note the two range markers at the north end, now gone, which used to define a line into the harbor.

from NOAA Coastal Map/EVS

This image is derived from the electronic version of paper charts (raster charts) published during the Big Dig. It seems to imagine a "biggest case scenario" in which dry landfill extends out to the old 6 foot contour. Charts like this were still in wide circulation in 2006, but the island never got this big.


Aerial photo of Spectacle in 2005, several years after filling was completed. The length of the island is little changed, but the narrow middle has thickened substantially. Detail has been removed from the water regions of this image (eg Sculpin Ledge is not visible), but the green areas along the east (right) coast correspond closely to the intertidal zone in the old chart.


In this image the land portion of the aerial photo is superimposed on the old chart, suggesting that the new landmass, while thicker in the middle than before, doesn't completely cover the old intertidal zone.


This shows the landmass (yellow), intertidal (green) and 6 foot contour (light blue) from NOAA's 2007 ENC (Electronic Navigation Chart, vector format) superimposed on the old chart. Here the landmass agrees with the aerial photo, while the intertidal around the north half of the island extends out to the old 6 foot contour.


NOAA's 2007 RNC (Raster Navigation Chart) also shows the enlarged intertidal zone around the north half of the island. The dashed border around green areas indicates they are insufficiently surveyed.

This composite image suggests how Spectacle approximately looks in 2007. The east side has long been surrounded by rocks and shallows, and it is not well charted following the Big Dig alterations to the island.