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Details for Benchmark: AL6484

N 28° 03.283 W 082° 26.883 (NAD 83)

Altitude: 34.02

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

Location:
In HILLSBOROUGH county, FL View Original Datasheet
Designation:
J 257
Marker Type:
bench mark disk
Setting:
set into the top of a round concrete monument
Stability:
May hold, but of type commonly subject to surface motion.

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Documented History (by the NGS)

01/01/1965 by CGS (MONUMENTED)
01/01/1966 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1966 1.8 MI N FROM TAMPA. ABOUT 1.8 MILES NORTH ALONG THE SEABOARD AIR LINE RAILROAD FROM SULPHUR SPRINGS STATION AT TAMPA, ABOUT 120 YARDS NORTH OF THE CROSSING OF FOWLER AVENUE, NEAR THE SOUTHWEST CORNER OF 8-BY-14-FOOT STEEL FENCE AROUND AN AUTOMATIC GAS PUMP NO. AA-156, 30.0 FEET EAST OF THE EAST RAIL, 1 FOOT SOUTH OF THE SOUTHWEST CORNER OF THE FENCE, 1.3 FEET NORTH OF A METAL WITNESS POST, ABOUT 3 FEET BELOW THE LEVEL OF THE TRACK AND SET IN THE TOP OF A CONCRETE POST PROJECTING 0.2 FOOT.
03/19/1991 by USPSQD (GOOD)
RECOVERY NOTE BY US POWER SQUADRON 1991 (RF) RECOVERED IN GOOD CONDITION.

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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