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Details for Benchmark: GQ0012

N 36° 43.867 W 112° 05.633 (NAD 83)

Altitude: 6504.67

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

Location:
In COCONINO county, AZ View Original Datasheet
Designation:
M 51
Marker Type:
bench mark disk
Setting:
in rock outcrop
Stability:
Most reliable and expected to hold position/elevation well.

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N 36° 43.891 W 112° 05.721

Recovered in good condition.

After making several (6 or 7)attempts for this mark I decided to do what I suggest to others. I chose 2 points that I knew the listed mileage from Houserock was correct and then measured the required distances from them. L 51 was the closest benchmark that we had found and the distance was 1 1/2 miles from it. It matched up with the measurement from the other point exactly.

After determining where the mark should be located I grabbed the metal detector and headed over to the outcrop that looked the most promising. After a sweep of that first area I move towards the east scanning for exposed bedrock. I saw one area about 50 feet away and moved over to it. Before even reaching the exposed rock I could see the epoxy used to hold the benchmark. At this point the only thing that went through my mind was "sh--, I didn't even need the metal detector!". It was in plain sight and had only a few pine needles on it.

The mark's location is visible from the highway if you look in the right place (see our pictures).

[Photos:]
photoM 51 in Northern Coconino County
photoM 51 looking easterly
Arrow points to the mark.
photoM 51 looking southernly
Arrow points to the mark.
photoM 51 parking spot
Arrow points to the mark just out of view to the right.
photoM 51 view from the highway
photoM 51 view from the highway 2
photoM 51 view from the highway close up
Camera zoomed all the way in. Picture taken from the truck parking spot.

Did a final search for it on 10/12/09. Tried metal detecting in a couple more likely looking spots but came up empty handed. I did find some evidence that I was in the correct area, such as a PK nail, a broken light bulb, some wooden slats and nails,but it was not to be.

I met up today with half of 2OF to search for for M 51. Highway improvements have wiped out the referenced culvert but the described distance from the centerline does point to an obvious ridge between two washes, one flowing SE parallel to the highway and the other flowing east. We searched several areas where the limestone is exposed, and John ran the metal detector over some of the soil covered areas, but were unable to come up with the find. I agree with him that the mark is probably still here but has been hidden away by the forces of nature.

Documented History (by the NGS)

01/01/1934 by CGS (MONUMENTED)
DESCRIBED BY COAST AND GEODETIC SURVEY 1934 4.5 MI W FROM HOUSE ROCK SPRINGS. 4.5 MILES WEST ALONG U.S. HIGHWAY 89 FROM HOUSE ROCK SPRINGS, COCONINO COUNTY, 100 FEET SOUTHWEST OF AN 18-INCH CORRUGATED-IRON PIPE CULVERT, 108 FEET SOUTH OF THE CENTERLINE OF THE HIGHWAY, AT A RAMP LEADING DOWN INTO A WASH, AND IN THE TOP OF A LIMESTONE OUTCROP FORMING A RIDGE BETWEEN TWO INTERSECTING WASHES. A STANDARD DISK, STAMPED M 51 1934.

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 1992. * This is a POSTED BENCH MARK height. Code A indicates a distribution rate of 0.0 thru 1.0 mm/km.
  • 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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