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Details for Benchmark: HV4519

N 38° 53.535 W 077° 02.009 (NAD 83)

Altitude: 6

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

Location:
In DISTRICT OF COLUMBIA county, DC View Original Datasheet
Designation:
15 CON
Marker Type:
survey disk
Setting:
setting not listed - see description
Stability:

Reference Points

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No luck - may still be covered..

Good references (incl the chiseled X on the manhole cover), but no disk.

The various landmarks - including the Pepco manhole X - were located, but not the disk itself. Possibly it is destroyed, or perhaps it is under the large concrete planter/security barrier pictured in the second photo.

[Photos:]
photoX on rim of manhole as mentioned in description of 15 Con, Washington, DC
photoProbable site of missing 15 Con, Washington, DC
If it still exists, the survey disk is probably under this large concrete planter. The manhole with the X on its rim is to the right, near the curb. The SUVs are driving west along Constitution Avenue, crossing 15th Street. Of course, that's the Washington Monument in the distance.

Documented History (by the NGS)

01/01/1981 by CANDA (MONUMENTED)
DESCRIBED BY CERVANTES AND ASSOCIATES 1981 (GCC) THE SURVEY POINT IS A PUNCH HOLE LOCATED IN THE OPENING OF THE LETTER C IN A 3-1/2 INCH DIAMETER BRASS DISK. STATION IS LOCATED IN THE SIDEWALK ON THE NORTHEAST CORNER OF 15TH STREET N.W. AND CONSTITUTION AVE. N.W. STATION IS 12.94 FT NE OF X ON RIM PEPCO M.H. STATION IS 20.34 FT NW OF SIGNAL POST BASE ON CON. AVE. STATION IS 8.56 FT SE OF SIGNAL POST BASE ON 15TH STREET.

Control Text

  • The horizontal coordinates were established by classical geodetic methods and adjusted by the National Geodetic Survey in November 1994.
  • The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)
  • The Laplace correction was computed from DEFLEC99 derived deflections.
  • The geoid height was determined by GEOID99.

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