Details for Benchmark: HT3458
N 37° 43.144 W 122° 30.253 (NAD 83)
Coordinates may not be exact. Altitude is SCALED and location is ADJUSTED. (more info)
- In SAN FRANCISCO county, CA View Original Datasheet
- BLACK BLUFF 3 1929
- Marker Type:
- NGS Benchmark
- setting not listed - see description
- Mark of questionable or unknown stability.
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Documented History (by the NGS)
|01/01/1929 by CGS (MONUMENTED)
|DESCRIBED BY COAST AND GEODETIC SURVEY 1929 (OWS)
THE STATION IS ESTABLISHED ON THE TOP OF THE HIGHEST KNOLL ABOUT 300 FEET W OF THE END OF THE MACADAM ROAD RUNNING PARALLEL WITH THE OCEAN AND W OF LAKE MERCED. AN ARMY DIRIGIBLE HANGER IS SITUATED ABOUT 1000 FEET AWAY IN A NORTHEASTERLY DIRECTION. THE CENTER OF THE EMERGENCY HOSPITAL ON THE SEAWARD SIDE OF FLEISHACKER POOL IS IN RANGE WITH THE CLIFF HOUSE.
THE STATION IS MARKED BY A STANDARD DISK SET IN A CONCRETE POST, OCTAGON SHAPE, 10 INCHES ACROSS THE TOP AND 2-1/2 FEET LONG, SUNK IN THE GROUND WITHIN 4 INCHES OF THE TOP.
REFERENCE MARK NO. 1 IS A 5-INCH SQUARE CONCRETE POST, 2 FEET LONG, SUNK IN THE GROUND WITHIN 6 INCHES OF THE TOP WITH A STANDARD REFERENCE DISK SET IN THE TOP AND THE ARROW POINTING TO THE STATION. THE MARK IS 5.82 METERS SE OF THE STATION AND ON RANGE WITH A CIRCULAR PATCH OF WOODS JUST BELOW SAN BRUNO MT.
REFERENCE MARK NO. 2 IS A 10- BY 12-INCH CONCRETE POST 2-1/2 FEET LONG, SUNK IN THE GROUND WITHIN 8 INCHES OF THE TOP WITH A STANDARD REFERENCE DISK SET IN THE TOP AND THE ARROW POINTS TO THE STATION. THE MARK IS 43.69 METERS N OF THE STATION AND ON RANGE WITH THE SOUTHERNMOST GUN MOUNTED ON A KNOLL ON THE SHORE SIDE OF THE MACADAM ROAD.
|01/01/1952 by CGS (MONUMENTED)
|RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1952 (WHB)
STATION IS DESTROYED. THE TOP OF THE HILL WAS CUT AWAY IN 1938 OR 1939 AND A MAN-MADE HILL ERECTED FOR AN ARMY INSTALLATION.
|01/01/1985 by USPSQD (MARK NOT FOUND)
|RECOVERY NOTE BY US POWER SQUADRON 1985 (MJS)
MARK NOT FOUND.
- The horizontal coordinates were established by classical geodetic methods and adjusted by the National Geodetic Survey in March 1994. 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.