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In KINGS county, NY
view original datasheet

N 40° 40.350 W 073° 58.100  (NAD 83)
Altitude: 146.37
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)

Designation: S 347
Marker Type: bench mark disk
Setting: massive structures
Stability: Probably hold position/elevation well.



Nearest:Benchmarks, Geocaches

Write note 3/21/2006 Papa-Bear-NYC posted a note for KU1296 (NGS Benchmark)   [visit log]
Historical Note:

In 1909, the New York City Board of Estimate and Apportionment (abbreviated NYBE+A) commisioned a survey of all five boroughs of New York City. This was the first city-wide survey to be done after the consolidation of the five boroughs into the City of New York in 1898. The survey would replace numerous incompatible systems in use by many city agencies, such as the highway department, the water department, the Department of Docks, etc. There were over 1000 benchmaks set in all, and the marks in Brooklyn go from #178 (at Fort Hamilton) to #504 (at the bulkhead on Newtown Creek at Manhattan Avenue, across from Queens), or 327 marks in all for Brooklyn. Of these, just 23 (that I know of) were put into the NGS database in 1952. You can tell if you get one of these Brooklyn marks if the designation is a number between 178 and 504.

The whole project and descriptions of each mark can be found in the volume Precise Leveling in New York City by Frederick W. Koop, published in 1914 and available in the New York Public Library. Mr. Koop was head of the surveying team that set the marks.

A number of these historic marks are lost, but many are still around if you just know where to look. Three of the bench marks from this original 1909 survey survive just across Flatbush Avenue from this station. Two (#381, a disk, and #382, a chiseled cross) are on the arch (the Soldiers and Sailors Monument) in the center of the Plaza and the third (#387, a copper bolt) is on the step of the round granite structure directly across the street.

#381 is particularly noteworthy. It is a 2 inch brass disk inscribed "BD. OF EST. & AP.". There were fewer than 20 of these disks used in the entire city, and this one is in the best condition of any I have found. These are the only bench marks used that are what we would immediatly recognize as a "Bench Mark Disk".

I have included pictures and directions to these marks. They're not in the NGS database, so if you find them, you get "extra credit" or you can waymark them. Have fun!


[This entry was edited by Papa-Bear-NYC on Thursday, March 23, 2006 at 1:39:42 PM.]

Photos:
photo NYBE+A #381 & #382, Grand Army Plaza, Brooklyn NY
View of the Soldiers and Sailors Monumental Arch from the southwest on the Prospect Park side of Grand Army Plaza. #381 is on the west face and #382 is on the east face (out of site).
photo NYBE+A #381, Grand Army Plaza, Brooklyn NY
View of the west face of the arch showing the location of the mark.
photo NYBE+A #381, Grand Army Plaza, Brooklyn NY
There were less than 20 of these disks set and this one is in the best condition of any I have found.
photo NYBE+A #382, Grand Army Plaza, Brooklyn NY
This is the door on the east face of the arch. The mark is a chiseled cross on the door sill.
photo NYBE+A #382, Grand Army Plaza, Brooklyn NY
The chiseled cross on the door sill.
photo NYBE+A #387, Grand Army Plaza, Brooklyn NY
This is the circular granite structure on the left side (east) of the main entrance to Prospect Park at Grand Army Plaza. It is right across Flatbush Avenue from the Library (visible in the background). The mark is a 7/8" copper bolt in front of the granite column on the left side of the entrance to the structure.
photo NYBE+A #387, Grand Army Plaza, Brooklyn NY
The 7/8" copper bolt on the step of the structure.
 
Found it 2/16/2006 Papa-Bear-NYC found KU1296 (NGS Benchmark)   [visit log]
Found as described. The construction is still in progress. The mark is at the "Staff" entrance on the Eastern Parkway side, just past the wooden construction fence.
Photos:
photo KU1296 "S 347" setting, Brooklyn Library
View from the corner of Eastern Parkway and Flatbush Avenue. The "Staff" entrance is past the left end of the wooden construction fence, just out-of-site from this angle.
photo KU1296 "S 347" setting, Brooklyn Library
The "Staff" entrance. This is serving as the general public entrance during the construction. The mark is outlined by a yellow rectangle.
photo KU1296 "S 347", Brooklyn Library, Brooklyn NY
 
Found it 7/11/2005 LeoGeo found KU1296 (NGS Benchmark)   [visit log]
It's there, and still visible despite the construction on the plaza in front of the library. It's just outside the construction fence. The library is designed to look like an open book standing up; the main entrance is the (curved) spine of the book, and this wing of the building is the back cover (or, if the book opens the other way as a book in Arabic or Hebrew or other right-to-left language would, the front cover). The wing paralleling Flatbush Ave. is the other cover.
 

Documented History (by the NGS)

1/1/1952 by CGS (MONUMENTED)
DESCRIBED BY COAST AND GEODETIC SURVEY 1952 AT NEW YORK. AT NEW YORK, IN BOROUGH OF BROOKLYN, AT GRAND ARMY PLAZA, AT NORTH CORNER OF PROSPECT PARK, AT EASTERN PARKWAY AND FLATBUSH AVENUE, SET VERTICALLY IN NORTH FACE OF BROOKLYN PUBLIC LIBRARY, 5 FEET WEST OF CENTER OF STAFF ENTRANCE TO BASEMENT, 0.8 FOOT ABOVE BASEMENT ENTRANCE CURBING AND 1 1/2 FEET ABOVE LEVEL OF SIDE WALK.

Control Text

  • The horizontal coordinates were scaled from a topographic map and have an estimated accuracy of +/- 6 seconds.
  • The orthometric height was determined by differential leveling and adjusted by the National Geodetic Survey in June 1991.
  • The geoid height was determined by GEOID99.
  • The dynamic height is computed by dividing the NAVD 88 geopotential number by the normal gravity value computed on the Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 degrees latitude (g = 980.6199 gals.).
  • The modeled gravity was interpolated from observed gravity values.

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