Nosy Neighbor: What’s This Thing Embedded in the Sidewalk?

I hope it’s new or else I really need to work on my powers of observation. What is it? —D.

I was at the intersection of Church and Leonard when I first noticed one: a marker, about the diameter of a tennis ball, embedded in the sidewalk. I was pretty sure I’d never seen one before. Poking around online, I found someone to email about it: Hector Rivera, Topographical Bureau Associate at the Manhattan Borough President’s Office. Here’s what he wrote back:

“This is a Manhattan Monument, used by surveyors to identify property lines. I have attached a PDF of the Manhattan Borough Survey Map, which shows the coordinates for that monument. There are two types of markers throughout the city. You have your Monuments that have longitude and latitude. Then you have the Bench Marks, also throughout the city, that will give you the elevation about sea level based on Manhattan Datum. Theses items have been in use for years and are still in use even with GPS equipment, especially in Manhattan (because of all the tall buildings, GPS equipment can only provide a correct read at certain times of the day when the GPS equipment has a straight uninterrupted signal to the satellite in space).”

Pictured below is a detail from the Survey Map (of the Church/Leonard intersection); I added the arrow to indicate where the Monument I noticed is. The map has black dots—which Rivera said indicate Monuments—all over. So how come I don’t see them everywhere? “Some of the markers are below grade and have square covers,” said Rivera.

Survey mapNote: D.’s question is recent, but the answer is mainly the same as from this 2011 post.

Got a question? Email tribecacitizen@gmail.com.

Previous Nosy Neighbor posts:
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Is Distilled now a café during the day?
Wasn’t the World Trade Center Greenmarket supposed to be open by now?
What’s the YogaSmoga townhouse on Greenwich?
Why are these people gathering on Broadway?
What are those things at Warren and Church?
Who were those people marching?
Why does 3 World Trade Center have tailpipes?
What’s that thing on 60 Hudson’s roof?
Why is this statue behind a fence?
Why does 1 World Trade Center look so unfinished at night?
Why do Brookfield Place’s escalators run that way?
What is Stadium Goods?
Why is the Duane Park flag almost always at half-staff?
What is Maison di Prima?
Where can I get breakfast in Tribeca?
Who are the Goatsingers?
Why was this cornice removed?
What’s coming to the Cosmopolitan Hotel’s storefronts?
What’s this two-year subway construction project?
What are those doodads on 60 Vestry?
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What’s that new building next to 30 Park Place?
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How come film shoots have a trailer with doors marked “Lucy” and “Desi”?

 

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