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Details for Benchmark: KU1645

N 40° 51.300 W 073° 57.650 (NAD 83)

Altitude: 283.02

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

Location:
In BERGEN county, NJ View Original Datasheet
Designation:
PALISADES RM 2
Marker Type:
reference mark disk
Setting:
in rock outcrop
Stability:
Most reliable and expected to hold position/elevation well.

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See Papa-Bear-NYC's superb essay, below. I concur with his conclusions. I think we confirmed that the stem is RM2 as well as could be expected from conscientious amateurs, and the metal detector found no other metallic objects in the immediate vicinity.

Today I met Seventhings and we had a closer look at this station. We did several things:

1) measured the mark
2) examined the rock ledge for erosion
3) measured the distance from station "PALISADES" with a tape
4) used my GPS averaging function to get as good a position and elevation of this mark as is feasible with a handheld GPS.

[b][u]1) Mark Measurements:[/u][/b] The stem was 5/8 inch in diameter and the top was 3/4 inch in diameter. See the first two photos. This is consistant with the dimensions of a 1930 CGS disk with the top cut off.

[b][u]2) Rock Erosion:[/u][/b] The ledge showed definite signs of erosion of a top layer about 1/4 to 1/2 inch thick which was flaking away. Several such flakes were sitting on the surface of the ledge. The 3rd photo shows a flake next to the mark (it was loose - we put it there) and shows an entire area around the mark which was light colored rock and which appears to have flaked away from the darker colored ledge (darker color rock is in upper right). This strongly implies that the mark's top was originally flush with the rock and the approximate 1/2 inch gap present now was caused by erosion of the ledge out from under the mark.

[b][u]3) Tape:[/u][/b] We measured the distance with tape from "PALISADES" to this mark. We measured 107' 2" compared to 104' 6" on the datasheet. The tape was not straight and had to go up and down and left and right through bushed. We thought the discrepancy of 2' 8" was reasonable, but in any case we carefully searched the ledge within 3 feet of the mark and there were no signs of any other possible marks (no holes, no imprints, etc.) We also scanned the whole area with a metal detector. We are satisfied that this is the mark described on the datasheet.

[b][u]4) GPS:[/u][/b] The Garmin 60CS was set to average for 500 samples. The results were:

[b]GPS Location:[/b] N 41:51:07.5 W073:57:39.3

Using the INVERSE program and computing from PALISADES gives
distance 32.53 meters
azimuth 197:47

Compared to the "box score"
distance 31.85 meters
azimuth 200:13

[b]GPS Elevation:[/b] 287 feet

The adjusted elevation from the datasheet is 283.02 feet

[b]GPS conclusion:[/b] The location and elevation of the mark are correct to well within the accuracy of the GPS. Furthermore, there are no other sites within the margin of error that has a mark or a remnant of a mark.

[u][b]Overall Conclusion:[/u][/b] The mark examined is at the position of this station and it is probably the stem of the original disk.

[Edit: fix a few typos and a misstyped distace measured by tape]

[This entry was edited by Papa-Bear-NYC on Friday, October 13, 2006 at 5:51:35 PM.]

[Photos:]
photoKU1645 "PALISADES RM 2", Fort Lee, NJ
Measurement showing a top diameter of 3/4 inch.
photoKU1645 "PALISADES RM 2", Fort Lee, NJ
Measurement showing a stem diameter of 5/8 inch.
photoKU1645 "PALISADES RM 2", Fort Lee, NJ
A rock flake found on the ledge placed next to the mark. Note the dark colored rock in the upper right which is presumed to be the original uneroded surface.

PALISADES RM 2 is of special interest. It was reported in 1930, when it was set as a reference mark for PALISADES (see [url=http://www.geocaching.com/mark/details.aspx?Pid=KU3890]KU3890[/url]), as a CGS Reference Mark Disk and recovered twice more in the 1930s as such. In 1956 it was used in a level line as a bench mark and given this PID, and again reported as a CGS Reference Mark Disk. But in 2001, the Port Authority reported that it was a brass plug, not a disk.

I looked very carefully and it seems to me that it is quite possibly the stem of a disk whose top has been cut off. Look at the close-up and you will see what look like hack saw marks coming from several directions. So I'm of the opinion that the original stem [i]may[/i] still be there after all. The PA reported a punch hole, but the close-up shows a little mass of broken brass in the center of the top, not a hole.

As a rererence mark it serves quite well. However it's value as a bench mark is clearly lost, whether it's a cut off disk, or a brass plug that replaced the disk.

Although the NGS prefers to count these as "Found, poor condition", as a practical matter no surveyor would use it, so as a bench mark it is destroyed.

[i]Logged with NGS on 10/2 as "Found, poor condition" with appropriate descriptions of what was observed.[/i]

[This entry was edited by Papa-Bear-NYC on Monday, October 02, 2006 at 1:53:03 PM.]

[Photos:]
photoKU1645 "PALISADES RM 2", Fort Lee, NJ
View of the location of the station. Walk along the path about 90 feet south of station KU3890, PALISADES and follow the herd path on the left towards the cliff.
photoKU1645 "PALISADES RM 2", Fort Lee, NJ
The rock ledge with the station mark.
photoKU1645 "PALISADES RM 2", Fort Lee, NJ
Close-up of mark. The top appears to show saw marks from several sides with a small mass near the center where the top was broken off. I suspect this may be the stem of the original disk which was possibly damaged and was cut away.

Found it.®

[Photos:]
photoKU1645

Found this one easily too, thanks to seventhings. Only the stem of the disk remains.

[Photos:]
photoKU1645
photoKU1645 View across the Hudson

Found as described by the Port Authority of NY & NJ in 2001 (see the current NGS datasheet). Handheld coordinates are N40-51.126 W073-57.656. See also KU3890.

[Photos:]
photoKU1645 PALISADES RM2
photoKU1645 in Fort Lee, Bergen Co., NJ
Looking east, the plug is at the white notebook, center.

Documented History (by the NGS)

Unknown by CGS (MONUMENTED)
01/01/1956 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1956 2.5 MI S FROM ENGLEWOOD CLIFFS. 0.15 MILE EAST ALONG PALISADES AVENUE FROM THE MUNICIPAL BUILDING AT ENGLEWOOD CLIFFS, THENCE 2.35 MILES SOUTH ALONG HUDSON AVENUE, ABOUT 200 METERS SOUTH OF GEORGE WASHINGTON BRIDGE, ON PROPERTY OF PORT OF NEW YORK AUTHORITY, SET IN TOP OF A ROCK OUTCROP, ABOUT 45 PACES SOUTHEAST OF THE SOUTHEAST CORNER OF A TWO STORY STUCCO HOUSE, 17 FEET NORTH OF THE SOUTHEAST CORNER OF A FENCE, 9 FEET EAST OF THE NORTH-SOUTH IRON FENCE.

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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