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Details for Benchmark: HS4126

N 37° 41.950 W 121° 47.117 (NAD 83)

Altitude: 439

Coordinates may not be exact. Altitude is VERTCON and location is SCALED. (more info)

Location:
In ALAMEDA county, CA View Original Datasheet
Designation:
C 1259
Marker Type:
bench mark disk
Setting:
light structures
Stability:
Mark of questionable or unknown stability.

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Documented History (by the NGS)

01/01/1974 by NGS (MONUMENTED)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1974 4.0 KM (2.50 MI) WEST FROM LIVERMORE. 2.5 MILES WEST ALONG INTERSTATE HIGHWAY 580 FROM THE STATE HIGHWAY (FIRST STREET) OVERPASS IN LIVERMORE, AT THE PORTOLA AVENUE OVERPASS, 66.5 FEET SOUTH OF THE SOUTH MOST CENTERLINE OF THE EAST BOUND HIGHWAY LANES, 140 FEET NORTHEAST OF THE CENTERLINE OF A FREEWAY EXIT ROAD, 52.9 FEET SOUTHEAST OF PADDLE BOARD ALA 13.21, 9.2 FEET SOUTHEAST OF THE SOUTHEAST CORNER OF A 3-BY 4-FOOT CONCRETE FOUNDATION OF A CATCH BASIN, AND A DISK ON THE TOP OF A 4-FOOT LENGTH OF COPPER COATED ROD WITH A BASE PLATE ATTACHED. THE DISK IS 0.2 FOOT UNDERGROUND AND IS PROTECTED BY A 4-INCH PLASTIC PIPE WHICH PROJECTS 0.1 FOOT AND IS ENCASED IN CONCRETE.

Control Text

  • 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  • The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.) The vertical order pertains to the superseded datum.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.

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