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Details for Benchmark: AA3903

N 41° 32.017 W 091° 32.617 (NAD 83)

Altitude: 637.6

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

Location:
In KEOKUK county, IA View Original Datasheet
Designation:
8 RESET
Marker Type:
vertical control disk
Setting:
setting not listed - see description
Stability:
Mark of questionable or unknown stability.

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Found 8 RESET 1975 in good condition at handheld coordinates N41 10.575 W092 23.248, 4.2 miles west of Main St in Hedrick, about 295 feet east of highway station post 65, about 145 feet west of a field driveway and old fence, 77 feet south of present highway center, 3 feet east southeast of power pole, 1 foot east of witness post, immediately north of a piece of concrete lying diagonally under surface, and 8 inches below surface. Sky visibility is clear except for power pole.

The two railroads which have passed through Hedrick are now gone and the depot has been moved from the south end of town to sit near the highway.

Disk is about 2 feet lower than road with handheld GPS elevation 801 feet (NAD 83). Topo map shows elevations just over 800 in the general vicinity.

The listed coordinates are for MG0512 Designation 8 (listed as Destroyed but USPSQD and I found it) in Johnson county and the listed elevation may relate to that mark as it does not appear reasonable here. I have been unable to find a listing for the (destroyed) PID in Keokuk county of the mark it replaced.

NGS has changed the coordinates for this mark to my handheld values (rounded).

[This entry was edited by Bill93 on Tuesday, January 22, 2008 at 3:21:45 PM.]

[Photos:]
photoAA3903_20040916_A.jpg
.
photoAA3903_20040916_C.jpg
photoMG0512_20040828_A the mark it was confused with
.
photoMG0512_20040828_C the mark it was confused with
.

Documented History (by the NGS)

1/1/1975 by NGS (MONUMENTED)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1975 (CLN) 4.25 MILES (6.84 KM) WEST ALONG STATE HIGHWAY 149 FROM THE RAILROAD CROSSING AND STATION IN HEDRICK, 94 FEET (28.7 M) SOUTH OF THE CENTER OF THE HIGHWAY, 3 FEET (0.9 M) WEST OF A POWER POLE AND 1 FOOT (0.3 M) EAST OF A METAL WITNESS POST, SET FLUSH WITH THE GROUND SURFACE.

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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