Central Park West Between 77th St and 75th St

The large looming buildings of the New York Historical Society and the American Museum of Natural History dominate this area of Central Park West. Because of it's popularity, plenty of street vendors call this area of town home. While it's true for practically any of the areas surrounding Central Park, I'm always a fan of the contrast between the park and the large buildings directly across the street. 

Can someone explain to me the signs that are posted near standpipes which indicate that a standpipe is nearby? Usually they're so close that the sign may as well be directly above it, rather than 12 feet to the left. Is there some legal requirement I'm unaware of?

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