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Details for Benchmark: MG0088

N 41° 28.833 W 090° 20.950 (NAD 83)

Altitude: 585.46

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

Location:
In HENRY county, IL View Original Datasheet
Designation:
RV 9
Marker Type:
rivet
Setting:
massive structures
Stability:
Probably hold position/elevation well.

Must Read!

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N 41° 28.852 W 090° 20.935

These coordinates were my best average reading of the mark.

Great area! Didn't know it existed. Got out of car to hear the sound of roaring water and discovered a small dam in the old locks of the Hennepin canal nearby. Crossed the footbridge and made my way towards the RR bridge. This time I'd actually brought the description and so knew what corner of the bridge to search.
Once I knew where to look, it was easy to find, though if it hadn't been for the paint around it, I don't know if I would have spotted it.

[Photos:]
photoHmmm
This is the first thing I saw once I got on the RR bridge. I stood my ground and the train backed down. (cough)
photoEast
View east down the tracks. I had thought that the other nearby benchmark might be at the bridge over the Green River in the distance, but after looking over a map after I got home, I see that is not the case.
photoHennepin Locks
photoHennepin lock 2
photothe benchmark
Benchmark on bridge support with canal about 30 ft below
photoMG0088
Close-up
N 41° 28.858 W 090° 20.938

Found easily, area around and including rivet has be painted with orange spray paint.

Found @ 1:04 pm, coordinats were off some, mine were N .853 W .931

Documented History (by the NGS)

Unknown by RIRR (MONUMENTED)
01/01/1935 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1935 AT COLONA. AT COLONA, HENRY COUNTY, ON THE CHICAGO, ROCK ISLAND AND PACIFIC RAILWAY, AT A BRIDGE OVER THE ILLINOIS-MISSISSIPPI CANAL, OPPOSITE CANAL LOCK 28, AND IN THE TOP OF THE SOUTHWEST END OF THE NORTHWEST CONCRETE ABUTMENT. A STANDARD MONEL-METAL RIVET.
07/17/1996 by USPSQD (GOOD)
RECOVERY NOTE BY US POWER SQUADRON 1996 RECOVERED IN GOOD CONDITION.

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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