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Details for Benchmark: MG0461

N 41° 26.017 W 091° 32.467 (NAD 83)

Altitude: 651.25

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

Location:
In WASHINGTON county, IA View Original Datasheet
Designation:
5
Marker Type:
NGS Benchmark
Setting:
setting not listed - see description
Stability:
Mark of questionable or unknown stability.

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Found in good condition, a small bronze disk cast with letters 'IHC BM' in center of west headwall at handheld coordinates N41 26.006 W091 32.501.

Culvert is just north of a farm field driveway, about 1/8 mile north of the large creek where bridge/culvert work is under way. Old Highway 218 is now a county road.

[Photos:]
photoMG0461_20040828_A.jpg
photoMG0461_20040828_C.jpg

Documented History (by the NGS)

1/1/1934 by IAHD (MONUMENTED)
DESCRIBED BY IOWA HIGHWAY DEPARTMENT 1934 7.2 MI N FROM RIVERSIDE. 7.2 MILES NORTH ALONG U.S. HIGHWAY 218 FROM THE OVERHEAD CROSSING OF THE CHICAGO, MILWAUKEE, ST. PAUL AND PACIFIC RAILROAD AT HASKINS, AT PAVEMENT STATION 1209, AT AN 8-1/2- BY 4-FOOT DOUBLE CULVERT, AND IN THE TOP OF THE WEST HEADWALL. A BRONZE PLUG.

Control Text

  • 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 June 1991.
  • 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.

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