Details for Benchmark: JW1748
N 39° 39.400 W 079° 26.883 (NAD 83)
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)
- In GARRETT county, MD View Original Datasheet
- SHA 248
- Marker Type:
- survey disk
- in rock outcrop
- Most reliable and expected to 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 2.3 MI (3.7 KM) WEST-SOUTHWEST OF FRIENDSVILLE, 7.1 MI (11.4 KM) WEST-NORTHWEST OF ACCIDENT, AND 1.6 MI (2.6 KM) EAST-SOUTHEAST OF THE MARYLAND-WEST VIRGINIA STATE LINE. IT IS LOCATED ON THE INTERSTATE HIGHWAY 68 RIGHT-OF-WAY. TO REACH FROM A POINT WHERE INTERSTATE HIGHWAY 68 CROSSES THE MARYLAND-WEST VIRGINIA STATE LINE, GO EAST ON INTERSTATE HIGHWAY 68 FOR 1.55 MI (2.49 KM) TO THE MARKER ON THE LEFT ALONG THE NORTH SIDE OF THE WESTBOUND LANE OF INTERSTATE HIGHWAY 68. THE POINT IS MARKED WITH A MARYLAND STATE HIGHWAY ADMINISTRATION SURVEY DISK, CEMENTED IN A DRILL HOLE IN AN OUTCROP OF BEDROCK. IT IS 51.5 FT (15.7 M) NORTHEAST OF THE CENTER OF THE WESTBOUND LANE OF INTERSTATE HIGHWAY 68, 11.5 FT (3.5 M) NORTHEAST OF A CARSONITE WITNESS POST, 21.0 FT (6.4 M) NORTHEAST OF THE CENTER OF A DRAINAGE DITCH, AND 226.0 FT (68.9 M) NORTHWEST OF THE WEST END OF A METAL GUARDRAIL. IT IS ABOUT 8.0 FT (2.4 M) HIGHER THAN THE SURFACE OF INTERSTATE HIGHWAY 68.
- 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.