Details for Benchmark: HV1835
N 38° 53.367 W 077° 01.767 (NAD 83)
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)
- In DISTRICT OF COLUMBIA county, DC View Original Datasheet
- J 5
- Marker Type:
- bench mark disk
- galvanized steel pipe
- Probably hold position/elevation well.
Benchmarks may be on private property or in dangerous locations. Obey local laws. By using the services on Geocaching.com you agree to this disclaimer.
Documented History (by the NGS)
|01/01/1971 by NGS (MONUMENTED)
|DESCRIBED BY NATIONAL GEODETIC SURVEY 1971
AT WASHINGTON. AT WASHINGTON, D.C., ABOUT 0.1 MILE SOUTH OF THE MAIN ENTRANCE TO THE MUSEUM OF HISTORY AND TECHNOLOGY AT THE SMITHSONIAN INSTITUTE, IN THE MALL BETWEEN WASHINGTON DRIVE AND ADAMS DRIVE, 42.8 FEET EAST OF THE EAST EDGE OF A CONCRETE CURB OF SW 13TH STREET, 78.8 FEET SOUTH AND ACROSS WASHINGTON DRIVE FROM A LIGHT POLE, 64.2 FEET NORTH-NORTHEAST OF THE CENTER OF A METAL MANHOLE COVER, 38.5 FEET SOUTHWEST OF THE SOUTHWEST CORNER OF A CONCRETE FOUNDATION AROUND A LARGE METAL MANHOLE, 21.5 FEET EAST OF THE EAST EDGE OF A SIDEWALK, 20.9 FEET SOUTH OF THE SOUTH EDGE OF THE SOUTH CONCRETE CURB OF WASHINGTON DRIVE, AND ON THE TOP OF A COPPER COATED ROD WHICH IS 5 INCHES BELOW THE SURFACE OF THE GROUND AND IS PROTECTED BY A 6-INCH PIPE WHICH IS 4 INCHES BELOW THE SURFACE OF THE GROUND. THE ROD WAS DRIVEN TO REFUSAL AT A DEPTH OF 23 FEET.
- 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.