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Details for Benchmark: NJ0540

N 42° 01.767 W 091° 33.517 (NAD 83)

Altitude: 807.05

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

Location:
In LINN county, IA View Original Datasheet
Designation:
T 80
Marker Type:
bench mark disk
Setting:
massive structures
Stability:
Probably hold position/elevation well.

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A topo map shows the railroad as being elevated at least 19 feet where it crosses the creek. The rail bed can be seen on the east side of the creek and a mound on the west side, but a lot of dirt in between has been removed. There is nothing left of the bridge except possibly some pieces of concrete pushed off to the side, none as big as an abutment. The creek may not be exactly where it used to be, but is presently at about N42 01.794 W091 33.563, about 170 ft NW of published coordinates, which is a typical offset and direction around here for scaled coordinates.

[This entry was edited by Bill93 on Tuesday, September 21, 2004 at 6:33:15 PM.]

[Photos:]
photoNJ0540_20040930_A.jpg

Documented History (by the NGS)

01/01/1934 by CGS (MONUMENTED)
DESCRIBED BY COAST AND GEODETIC SURVEY 1934 2 MI E FROM MARION. 2.0 MILES EAST ALONG THE CHICAGO, MILWAUKEE, ST. PAUL AND PACIFIC RAILROAD FROM THE STATION AT MARION, LINN COUNTY, AT MILEPOST 225, AT A 30-FOOT CONCRETE ARCH BRIDGE, IN THE TOP OF THE SOUTH END OF THE EAST CONCRETE ABUTMENT, 10 FEET SOUTH OF THE CENTERLINE OF THE SOUTH TRACK, AND 2 FEET LOWER THAN THE TRACK. A STANDARD DISK, STAMPED T 80 1934.
05/04/1994 by USPSQD (MARK NOT FOUND)
RECOVERY NOTE BY US POWER SQUADRON 1994 MARK NOT FOUND.

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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