Details for Benchmark: JW1729
N 39° 41.767 W 079° 16.700 (NAD 83)
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)
- In GARRETT county, MD View Original Datasheet
- SHA 229
- Marker Type:
- survey disk
- massive structures
- 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 1.6 MI (2.6 KM) WEST OF KEYSERS RIDGE, 5.1 MI (8.2 KM) NORTH-NORTHEAST OF ACCIDENT, AND 10.8 MI (17.4 KM) EAST-NORTHEAST OF THE MARYLAND-WEST VIRGINIA STATE LINE. IT IS LOCATED ON THE INTERSTATE HIGHWAY 68 RIGHT-OF-WAY. TO REACH FROM A POINT WHERE U.S. HIGHWAY 219 PASSES OVER INTERSTATE HIGHWAY 68 NEAR KEYSERS RIDGE, GO WEST ON INTERSTATE HIGHWAY 68 FOR 1.75 MI (2.82 KM) TO A POINT ABOUT 0.15 MI (0.24 KM) NORTHWEST OF A HIGHWAY MILE MARKER NUMBERED 12 AND THE MARKER ON THE LEFT IN THE MOST NORTHERLY ONE OF TWO LARGE CONCRETE FOUNDATIONS FOR A HIGHWAY SIGN. THE POINT IS MARKED WITH A MARYLAND STATE HIGHWAY ADMINISTRATION SURVEY DISK, CEMENTED IN A DRILL HOLE IN THE NORTHWEST SIDE OF THE MOST NORTHERLY ONE OF TWO 3.0 FT (0.9 M) ROUND CONCRETE BASE FOR A LARGE HIGHWAY SIGN MARKING INTERSTATE HIGHWAY 68 EXIT NUMBER 14 AND FOOD. IT IS 35.0 FT (10.7 M) SOUTHWEST OF THE CENTER OF THE EASTBOUND LANES OF INTERSTATE HIGHWAY 68, 4.0 FT (1.2 M) SOUTHWEST OF THE CENTER OF A DRAINAGE DITCH, AND 212.0 FT (64.6 M) NORTHWEST OF THE CENTER OF A LONE DROP INLET. IT IS ABOUT 1.0 FT (0.3 M) LOWER 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.