Details for Benchmark: LX3064
N 41° 34.000 W 072° 38.750 (NAD 83)
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)
- In MIDDLESEX county, CT View Original Datasheet
- B 92
- Marker Type:
- bench mark disk
- abutments and piers of large bridges
- Probably hold position/elevation well.
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Documented History (by the NGS)
|01/01/1986 by NGS (MONUMENTED)
|DESCRIBED BY NATIONAL GEODETIC SURVEY 1986
1.2 KM (0.75 MI) WEST FROM PORTLAND. 1.2 KM (0.75 MI) WEST ALONG THE CONRAIL RAILROAD FROM THE STATE HIGHWAY 66 OVERPASS IN PORTLAND TO THE TRESTLE OVER THE CONNECTICUT RIVER AND THE MARK ON THE LEFT IN TOP OF THE SOUTHEAST END OF THE EAST ABUTMENT, 3.0 METERS (9.9 FT) SOUTH OF THE SOUTH RAIL. THE MARK IS 0.76 M BELOW RAIL.
- 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.