Details for Benchmark: HS4129
N 37° 42.150 W 121° 44.683 (NAD 83)
Coordinates may not be exact. Altitude is VERTCON and location is SCALED. (more info)
- In ALAMEDA county, CA View Original Datasheet
- E 1259
- Marker Type:
- bench mark disk
- copper-clad steel rod
- Probably hold position/elevation well.
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Documented History (by the NGS)
|01/01/1974 by NGS (MONUMENTED)
|DESCRIBED BY NATIONAL GEODETIC SURVEY 1974
0.6 KM (0.35 MI) WEST FROM LIVERMORE. 0.35 MILES WEST ALONG INTERSTATE HIGHWAY 580 FROM THE STATE HIGHWAY 84 (FIRST STREET) OVERPASS IN LIVERMORE, AT AN ANGLE IN THE SOUTH FREEWAY RIGHT OF WAY FENCE, 53 FEET SOUTH OF THE SOUTH MOST CENTERLINE OF THE EAST BOUND HIGHWAY LANES, 98.5 FEET WEST OF THE NORTHEAST END OF THE SOUTHEAST CONCRETE HEADWALL OF A TRIPLE CONCRETE BOX CULVERT, 2.0 FEET NORTH OF THE FENCE, 1.5 FEET EAST OF A METAL WITNESS POST, ABOUT 2 FEET LOWER THAN THE HIGHWAY, AND A DISK ON THE TOP OF A COPPER COATED ROD DRIVEN TO GRADUAL REFUSAL AT A DEPTH OF 19 FEET. THE DISK IS 0.3 FOOT UNDERGROUND AND IS PROTECTED BY A 4-INCH PLASTIC PIPE WHICH PROJECTS 0.2 FOOT AND IS ENCASED IN CONCRETE.
- The horizontal coordinates were scaled from a topographic map and have an estimated accuracy of +/- 6 seconds.
- The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.) The vertical order pertains to the superseded datum.
- The geoid height was determined by GEOID99.