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Details for Benchmark: HV8783

N 38° 55.733 W 077° 06.983 (NAD 83)

Altitude: 51.27

Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)

Location:
In ARLINGTON county, VA View Original Datasheet
Designation:
52 34
Marker Type:
triangulation station disk
Setting:
retaining walls, concrete ledge, etc.
Stability:
May hold, but of type commonly subject to surface motion.

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Found as described by Artman and BDT.

[Photos:]
photoCloseup of Station.
I counted 46 "indentations" on the disk.

Hard to see how the NGS could have placed this bench mark in Arlingwood, as stated in the 1990 description. The county name, of course, is Arlington. The station is located at the west (Virginia) end of Chain Bridge, just south of the end of the bridge. (Traveling between Virginia and DC would seem to be a north-south proposition, but actually the bridge orientation is closer to east-west.) The station is about 2 feet from Vepco pole EJ62, which has a streetlight at its top.

The stamping, which is also the designation, apparently refers to the elevation in feet, although the adjusted height of this first order vertical station is slightly different - 51.27 feet.

One mystery about the disk: the surface is covered with about 45 depressions small, round, irregularly-spaced depressions of unknown origin.

[Photos:]
photoCloseup of HV8783, Arlington, VA
photoView toward Chain Bridge, Arlington, VA
52 34 is indicated by yellow arrow

The triangulation station was found as described.

The disk is rather unusual. It is very thick, when viewed from the side. Also, the monumentation date is unknown to the NGS. I would guess it was from the 1930's, when the bridge was built. The marking on it, and its NGS designation, is 52 34, which I belive to be a stamped elevation of 52.34 feet. The elevation on the PID sheet is 51.27 feet, but the difference is probably due to geoid modeling differences.

[Photos:]
photoStation 52 34 in Arlington County, Virginia
The disk. The elevation stamped on it is 52.34 feet.
photoat station 52 34 in Arlington County, Virginia
The disk has a red arrow pointing to it. In the lower right of the picture is the Potomac River. The view on the left past the bridge railing is Maryland. The historical marker explains the history of Chain Bridge. The current structure was built around 1936, according to the sign.
photoat station 52 34 in Arlington, Virginia
A red arrow points out the disk's location. A yellow arrow shows where a surveyor spray painted the station's designation on the metal girder On the right side of the picture is the Virginia shore of the Potomac River and a stone structure that may be part of a former version of Chain Bridge.

Documented History (by the NGS)

Unknown by USGS (MONUMENTED)
04/10/1990 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1990 IN ARLINGWOOD, AT THE INTERSECTION OF CHAIN BRIDGE ROAD (STATE ROUTE 123) AND GLEBE ROAD (STATE ROUTE 120), IN THE SOUTH END OF THE SOUTHWEST CONCRETE WINGWALL OF CHAIN BRIDGE SPANNING THE POTOMAC ROVER, 70.3 M (230.64 FT) EAST OF THE EXTENDED CENTERLINE OF CHAIN BRIDGE ROAD, 6.5 M (21.33 FT) SOUTH-SOUTHWEST OF THE CENTER OF NORTH GLEBE ROAD, 0.7 M (2.30 FT) NORTHWEST OF UTILITY LIGHT POLE NUMBER EJ62, AND 0.6 M (1.97 FT) SOUTH-SOUTHWEST OF THE SOUTHWEST END OF THE CHAIN BRIDGE PARAPET WALL.

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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