Details for Benchmark: JT2042
N 38° 02.325 W 122° 06.822 (NAD 83)
Coordinates may not be exact. Altitude is SCALED and location is ADJUSTED. (more info)
- In CONTRA COSTA county, CA View Original Datasheet
- MAN 1949
- Marker Type:
- NGS Benchmark
- setting not listed - see description
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Documented History (by the NGS)
|01/01/1949 by CGS (MONUMENTED)
|DESCRIBED BY COAST AND GEODETIC SURVEY 1949 (CAG)
ON THE SOUTH SIDE OF SUISUN BAY, ABOUT 500 METERS EAST OF THE MARTINEZ END OF THE SOUTHERN PACIFIC R.R. BRIDGE IN THE TOP OF A DOLPHIN ABOUT 20 METERS OFFSHORE OF THE MARSH. AN IRON PIPE ABOUT 10 INCHES IN DIAMETER, FILLED WITH CONCRETE AND SURROUNDED BY PILINGS, MAKES UP THE DOLPHIN. THE STRUCTURE WAS ESTABLISHED BY THE SOUTHERN PACIFIC R.R. CO. AS A CONTROL POINT FOR THE CONSTRUCTION OF THE RAILROAD BRIDGE.
THE CENTER OF A CROSS, CUT IN A METAL SQUARE SET IN CONCRETE IN THE TOP-OF THE PIPE MARKS THE STATION. IT IS LOCATED BY A 3-POINT FIX AND USED FOR TOPOGRAPHIC CONTROL.
|01/01/1962 by CGS (MONUMENTED)
|RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1962 (IRR)
THE DOLPHIN AND IRON PIPE IN ITS CENTER WERE RECOVERED IN GOOD CONDITION AND SOLID AND THE 1949 DESCRIPTION IS ADEQUATE.
- 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.