Details for Benchmark: JW1719
N 39° 41.383 W 079° 15.000 (NAD 83)
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)
- In GARRETT county, MD View Original Datasheet
- SHA 225
- Marker Type:
- survey disk
- abutments and piers of large bridges
- Probably hold position/elevation well.
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Documented History (by the NGS)
|01/01/1992 by MDSHA (MONUMENTED)
|DESCRIBED BY MARYLAND DOT HIGHWAY ADMINISTRATION 1992
THE MARKER IS LOCATED ABOUT 0.3 MI (0.5 KM) SOUTH-SOUTHWEST OF KEYSERS RIDGE, 5.1 MI (8.2 KM) WEST OF GRANTSVILLE, AND 5.6 MI (9.0 KM) NORTHEAST OF ACCIDENT. IT IS LOCATED ON INTERSTATE HIGHWAY 68 RIGHT-OF-WAY. TO REACH FROM A POINT WHERE STATE HIGHWAY 495 CROSSES OVER INTERSTATE HIGHWAY 68 NEAR GRANTSVILLE, GO WEST ON INTERSTATE HIGHWAY 68 FOR 5.25 MI (8.45 KM) TO AN EXIT RAMP NUMBERED 14-A LEADING TO SOUTHBOUND U.S. HIGHWAY 219. LEAVE INTERSTATE HIGHWAY 68 AND GO WEST ON THE EXIT RAMP FOR 0.5 MI (0.8 KM) TO THE MARKER ON THE RIGHT IN THE BRIDGE ABUTMENT. THE POINT IS MARKED WITH A MARYLAND STATE HIGHWAY ADMINISTRATION SURVEY DISK, CEMENTED IN A DRILL HOLE IN THE WEST END OF A BACKWALL WHICH IS PART OF THE NORTH ABUTMENT OF A BRIDGE NUMBERED 11049 WHERE SOUTHBOUND U.S. HIGHWAY 219 CROSSES OVER THE WESTBOUND LANE OF INTERSTATE HIGHWAY 68 NEAR KEYSERS RIDGE. IT IS 0.7 FT (21.3 CM) NORTH OF THE MOST NORTHERLY BRIDGE EXPANSION JOINT, 2.3 FT (0.7 M) EAST OF THE EAST EDGE OF THE MOST WESTERLY BRIDGE PARAPET WALL, 10.0 FT (3.0 M) SOUTH OF THE NORTH END OF THE MOST WESTERLY BRIDGE PARAPET WALL, 27.5 FT (8.4 M) WEST OF THE CENTER OF U.S. HIGHWAY 219, 90.0 FT (27.4 M) SOUTHWEST OF A HIGHWAY OVERHEAD LIGHT POLE NUMBERED 5B 48 250, AND 102.0 FT (31.1 M) SOUTH OF ANOTHER OVERHEAD HIGHWAY LIGHT POLE NUMBERED 7B 47 250. IT IS ABOUT THE SAME ELEVATION AS THE SURFACE OF THE HIGHWAY.
- 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 April 1995.
- 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.