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Details for Benchmark: TZ1974

N 32° 55.606 W 118° 31.112 (NAD 83)

Altitude: 1102

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

Location:
In LOS ANGELES county, CA View Original Datasheet
Designation:
BLUFF
Marker Type:
NGS Benchmark
Setting:
setting not listed - see description
Stability:

Reference Points

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Station Mark recovered in good condition, however, the disc and monument are tilted slightly (estimated 20 to 30 degrees). The RM's were not found. Possible prior location of RM1 to the west found, with several possible disc stems or pins found in the rock. The mark can be driven to with a high clearance four wheel drive vehicle.

[Photos:]
photoTZ1974 Disc on San Clemente Island CA
photoTZ1974 Area on San Clemente Island CA
photoView over TZ1974 to the west
At the ocean, with the surf around it, you can see Eel Point. We didn't know it at the time, but we would end up there in a few days, and recover the mark there!
photoPossible prior location(s) of TZ1974 RM1

Documented History (by the NGS)

01/01/1862 by CGS (MONUMENTED)
01/01/1878 by CGS (GOOD)
DESCRIBED BY COAST AND GEODETIC SURVEY 1878 (SF) ON THE EXTREME END OF A BOLD POINT JUTTING OUT TO THE WESTWARD FROM THE RIDGE RUNNING UP TO THE NORTHEAST FROM SEAL HARBOR. THE CENTER WAS MARKED BY AN UNDERGROUND STONE WITH LEAD BOLT ONLY, AND A SURFACE STONE SIMILAR TO A STANDARD DISK SET INTO A MASS OF CONCRETE IN A DEPRESSION IN ROCK OUTCROP. TO THE NORTH OF THE STATION 6.8 FEET WAS A DRILL HOLE IN THE FIXED ROCK, AND A SIMILAR ONE TO THE SOUTH 6.2 FEET. TO THE EAST 9.4 FEET WAS A ROCK WITH A HOLE IN THE TOP SET EVEN WITH THE SURFACE OF THE GROUND.
01/01/1933 by CGS (SEE DESCRIPTION)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1933 (RWK) ON SAN CLEMENTE ISLAND, ON THE EXTREME END OF A BOLD POINT JUTTING OUT TO THE WESTWARD FROM THE RIDGE RUNNING UP TO THE NORTHEAST FROM SEAL HARBOR. TO THE NORTH IS A DOMED POINT WITH A ROCKY OUTCROP ON THE SOUTHERLY SIDE (TOWARD BLUFF). THE LAND TO THE SOUTHWEST OF THE STATION DROPS AWAY ABRUPTLY TOWARD THE SEA TO A LONG ROCKY POINT EXTENDING INTO THE OCEAN (EEL POINT). THE STATION LIES ABOUT 250 METERS EAST OF A WIRE LINE FENCE WHICH RUNS IN A NORTHEASTERLY DIRECTION ACROSS THE ISLAND. ALL MARKS RECOVERED. THE SURFACE AND SUB-SURFACE MARKS WERE REPLACED BY A STANDARD DISK, STAMPED BLUFF 1933, IN A CONCRETE POST. TWO OF THE OLD DRILL HOLE REFERENCE MARKS WERE ENLARGED AND REMARKED AS FOLLOWS--REFERENCE MARK NO. 1, A HYDROGRAPHIC TABLET STAMPED BLUFF REF. NO 1 1933, A DISTANT 1.845 METERS. REFERENCE MARK NO. 2, REFERENCE TABLET STAMPED BLUFF NO 2 1933, DISTANT 2.848 METERS.
01/01/1952 by CGS (GOOD)
RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1952 (NES) STATION WAS LOCATED AND FOUND AS DESCRIBED AND IN GOOD CONDITION OBSERVATIONS WERE MADE FROM A 4 FOOT STAND. NEW DISTANCES AND DIRECTIONS ARE GIVEN ABOVE
01/01/1984 by DMA (GOOD)
RECOVERY NOTE BY DEFENSE MAP AGENCY 1984 (MH) BLUFF 1933 RECOVERED GOOD. BLUFF REF. NO 1 1933 RECOVERED GOOD. BLUFF REF. NO 2 1933 THE ROCK IN WHICH REFERENCE MARK NO 2 IS SET IS LOOSE. MARKS RECOVERED AS DESCRIBED BY J.G. MORTENSEN OF DMA HTC IN 1978 ON A RECOVERY NOTE WITH NEW DESCRIPTION.
01/01/1985 by DMA (GOOD)
RECOVERY NOTE BY DEFENSE MAP AGENCY 1985 (JKB) BLUFF 1933 FOUND GOOD, RECOVERED AS DESCRIBED. RMS BLUFF NO. 1 1933, BLUFF NO. 2 1933 RMS IN GOOD CONDITION, RECOVERED AS DESCRIBED.

Control Text

  • The horizontal coordinates were established by classical geodetic methods and adjusted by the National Geodetic Survey in June 1996. The horizontal coordinates are valid at the epoch date displayed above. The epoch date for horizontal control is a decimal equivalence of Year/Month/Day.
  • The orthometric height was scaled from a topographic map.
  • The Laplace correction was computed from DEFLEC99 derived deflections.
  • The geoid height was determined by GEOID99.

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