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Details for Benchmark: DY0926

N 33° 43.933 W 118° 05.083 (NAD 83)

Altitude: 35.17

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

Location:
In ORANGE county, CA View Original Datasheet
Designation:
F 978 RESET
Marker Type:
bench mark disk
Setting:
pavements (street, sidewalk, curb, apron, etc.)
Stability:
Mark of questionable or unknown stability.

Must Read!

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This is a "bike to" mark, or a pretty long walk. No parking nearby, unless you are very brave or very silly. Recovered as described in the NGS database.

Mark is also an Orange County Surveyor GPS Horizontal Control mark, and as such, it's position is [i]very[/i] accurately known. In HDDD MM SS.SSSSS format:
N033 43 56.35732
W118 05 06.44196
Here is the OCS webpage:
http://www.ocgeomatics.com/landrecords/GeodeticDetail.aspx?txtControlPointN=0944&txtIsVertical=horizontal

If you are going by, it's a good place to check your GPS accuracy. My Delorme PN-20 was pretty good!

[Photos:]
photoDY0926 disc in Seal Beach CA
photoDY0926 looking North up Pacific Coast Hwy
The bike is Klemmer's transport for the day. Ended up with about 10 miles for the day.
photoDY0926 Disc, looking Northwest toward Long Beach
The round dome on the horizon is the old Howard Hughes Spruce Goose geodesic dome, next to the Queen Mary. Now part of the cruise ship terminal, I think.
N 33° 43.941 W 118° 05.108

Out for a bike ride. Noticed this one and stopped. Recovered in good condition. This is my fist official benchmark find. I am thrilled! As is always the case, the coordinates are not correct. I took a reading and added to this report.

The disk was indeed painted white. A little work with a wirebrush cleared that problem right up. BM is painted on the bridge pointing at the benchmark.

[Photos:]
photoDY0926 - Closeup of disk - Seal Beach, CA
I had to clean the paint off to get this clear image.
photoDY0926 - Area around disk - Seal Beach, CA
The disk is mounted in the sidewalk of the bridge.

I'm pretty sure this is it. I was confused by all the descriptions relative to guard rail, centerline, etc. (PCH runs SE-NW here), but this is on the southbound side of the bridge, near the north end. It screams "benchmark" with all the markings on the concrete.

[Photos:]
photoBenchmark
Unfortunately, they got white paint on it.

Documented History (by the NGS)

01/01/1967 by CGS (MONUMENTED)
01/01/1969 by CA-059 (GOOD)
DESCRIBED BY ORANGE COUNTY CALIFORNIA 1969 1.5 MI SE FROM SEAL BEACH. 1.50 MILES SOUTHEAST ALONG THE PACIFIC COAST HIGHWAY (U.S. 101 ALT.) FROM THE POST OFFICE TO THE CONCRETE BRIDGE NO. 55-10-1967 OVER ANAHEIM BAY, 35.4 FEET SOUTHWEST OF THE CENTER LINE OF THE HIGHWAY, 2.50 FEET SOUTHWEST OF THE NORTHEAST EDGE OF A CONCRETE SIDEWALK ACROSS THE CONCRETE BRIDGE, 16.7 FEET SOUTHEAST OF THE NORTHWEST END OF THE WALK, 2.7 FEET NORTHEAST OF THE GUARD RAIL, SET IN THE TOP OF A CONCRETE WALK, 0.8 FOOT HIGHER THAN THE HIGHWAY.
01/01/1973 by CA-059 (GOOD)
RECOVERY NOTE BY ORANGE COUNTY CALIFORNIA 1973 RECOVERED IN GOOD CONDITION.
01/01/1978 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1978 RECOVERED IN GOOD CONDITION.
04/06/1989 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1989 RECOVERED IN GOOD CONDITION. A NEW TO REACH FOLLOWS. 1.1 KM (0.70 MI) NORTHWESTERLY ALONG PACIFIC COAST HIGHWAY (STATE HIGHWAY 1) FROM THE JUNCTION OF ANDERSON STREET IN SUNSET BEACH.

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. WARNING-Repeat measurements at this control monument indicate possible vertical movement.
  • 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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