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Details for Benchmark: HS4127

N 37° 41.983 W 121° 46.417 (NAD 83)

Altitude: 463.6

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

Location:
In ALAMEDA county, CA View Original Datasheet
Designation:
A 446 B 1
Marker Type:
bench mark disk
Setting:
pavements (street, sidewalk, curb, apron, etc.)
Stability:
Mark of questionable or unknown stability.

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N 37° 41.973 W 121° 46.434

Found A446 as described and in good condition.

[Photos:]
photoHS4127 Environment
Looking north towards the 580 overpass.
photoHS4127

Found where described

[Photos:]
photofor reference
photoeye level
photomark
N 37° 41.976 W 121° 46.433

GPS readings showed within 17 feet of accuracy.
Located as described in 1974 description.

T&J (Scoobywatchers)

[Photos:]
photoA 446 B 1

Documented History (by the NGS)

01/01/1974 by CADH (MONUMENTED)
DESCRIBED BY CA DIV OF HIGHWAYS 1974 3.1 KM (1.95 MI) WEST FROM LIVERMORE. 1.85 MILES WEST ALONG INTERSTATE HIGHWAY 580 FROM THE STATE HIGHWAY 84 (FIRST STREET) OVERPASS IN LIVERMORE, THENCE 0.1 MILE SOUTH ALONG NORTH LIVERMORE AVENUE, AT A CONCRETE BRIDGE OVER ARROYO POSITAS, IN THE TOP OF THE WEST CONCRETE WALKWAY OF THE BRIDGE, 23.5 FEET NORTH OF THE SOUTHEAST CORNER OF THE WEST CONCRETE GUARDRAIL, 3.8 FEET EAST OF THE WEST CONCRETE GUARDRAIL, AND ABOUT 0.5 FOOT HIGHER THAN THE AVENUE.

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  • The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.) The vertical order pertains to the superseded datum.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