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Details for Benchmark: HT1855

N 37° 49.667 W 122° 12.717 (NAD 83)

Altitude: 637.4

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

Location:
In ALAMEDA county, CA View Original Datasheet
Designation:
M 1253
Marker Type:
bench mark disk
Setting:
abutments and piers of large bridges
Stability:
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 2.7 KM (1.70 MI) SOUTH FROM OAKLAND. 1.7 MILES SOUTH ALONG STATE HIGHWAY 13 FROM THE JUNCTION OF STATE HIGHWAY 24, AT A PEDESTRIAN OVERPASS, IN TOP OF THE EAST CORNER OF THE CONCRETE FOUNDATION FOR THE SOUTH-WESTERN MOST STEEL LEG FOR A SUPPORT PIER, 23.5 FEET SOUTHWEST OF THE CENTERLINE OF THE SOUTH BOUND LANES OF THE HIGHWAY, 0.5 FOOT EAST OF THE EAST CORNER OF THE CONCRETE FOUNDATION FOR A STEEL LEG, ABOUT 3 FEET HIGHER THAN THE HIGHWAY.

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  • The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.) The vertical order pertains to the superseded datum.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