[Nuttyman54]

342.24 as an elevation measurement....
342.24 inches = 28.52 feet
342.24 cm = 11.23 feet

the elevation of Boston is ~19 feet above sea level, so either one of those is plausible for the ground level of Copley Square

EDIT: Copley Sq is about 16 feet above sea level, so it's not the ground elevation. HOWEVER, if you look at the satelite view in Google Maps, it appears to be pointing DIRECTLY at a statue or post of some sort. This could be the elevation of the top of the statue, a plaque on the statue....anyone want to go take a look? (I would, but I'm in California at the present time)

EDIT #2: Statue appears to be of John Singleton Copley, the square's namesake. Famous for his paintings, parents were traders. Theres more on his wiki page. Hint could also just as easily involve the physical statue attributes, or his name (Singletons anyone?)

EDIT#3: Copley Square is the official finish line for the Boston Marathon (Credit to Ruth of 1735 for this one)