U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 Station ID: 8728288 PUBLICATION DATE: 05/12/2004 Name: ALLIGATOR POINT FL NOAA Chart: 11405 Latitude: 29° 54.2' N ( 29.90330) USGS Quad: ST. TERESA BEACH Longitude: 84° 24.8' W ( -84.41330) To reach the tidal bench marks from the junction of County Road C-370 (Alligator Drive) and U.S. Highway 98, south of Ochlockonee Bay, proceed south and west on County Road C-370 for 13.4 km (8.3 mi) to the Alligator Point Marina. The bench marks are located around the marina and along the road. The tide gage and staff were located on the marina seawall. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 290841 AA 1 1975 DESIGNATION: 290841 AA 1 MONUMENTATION: Survey disk VM#: 9799 AGENCY: Florida Department of Natural Resources (FLDNR) IDB PID#: AS0469 SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 29° 54.2' N ( 29.90330) LONGITUDE: 84° 25.0' W ( -84.41670) The primary bench mark is a disk located on the north side of County Road C-370 (Alligator Road), 140 m (460 ft) west of bench mark 290841 AA 2 1975, 5.73 m (18.8 ft) north of the centerline of County Road C-370, and 1.83 m (6.0 ft) east of powerline pole No. 59V-1297R. The bench mark is crimped to the top of a copper-clad steel rod driven 7.3 m (23.9 ft) to refusal, and encased in a PVC pipe and concrete kickblock. BENCH MARK STAMPING: 290841 AA 2 1975 DESIGNATION: 290841 AA 2 MONUMENTATION: Survey disk VM#: 9800 AGENCY: Florida Department of Natural Resources (FLDNR) IDB PID#: AS0468 SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 29° 54.2' N ( 29.90330) LONGITUDE: 84° 24.9' W ( -84.41500) The bench mark is a disk located on the north side of County Road C-370 (Alligator Drive), 36.58 m (120.0 ft) east of the entrance to the marina, 6.68 m (21.9 ft) north on the centerline of the road, 5.79 m (19.0 ft) east of powerline pole No. 58X802R, and 0.3 m (1 ft) south of a witness post. The bench mark is crimped to the top of a copper-clad steel rod driven 14.6 m (47.9 ft) to refusal, and encased in a PVC pipe and concrete kickblock. NOTE: Mark not found in 1998 by US Power Squadron.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 Station ID: 8728288 PUBLICATION DATE: 05/12/2004 Name: ALLIGATOR POINT FL NOAA Chart: 11405 Latitude: 29° 54.2' N ( 29.90330) USGS Quad: ST. TERESA BEACH Longitude: 84° 24.8' W ( -84.41330) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 290841 AA 4 1975 DESIGNATION: 290841 AA 4 MONUMENTATION: Survey disk VM#: 9801 AGENCY: Florida Department of Natural Resources (FLDNR) IDB PID#: AS0470 SETTING CLASSIFICATION: Concrete sea wall OPUS PID: LATITUDE: 29° 54.3' N ( 29.90500) LONGITUDE: 84° 25.0' W ( -84.41670) The bench mark is a disk set flush in the sea wall on the north side of the marina, 44 m (145 ft) east of the NW corner of sea wall, 24 m (80 ft) east of the NE corner of the Tackle Shop, and 1.15 m (3.7 ft) SW of the NE corner of the sea wall. BENCH MARK STAMPING: 290841 AA 5 1975 DESIGNATION: 290841 AA 5 MONUMENTATION: Survey disk VM#: 9802 AGENCY: Florida Department of Natural Resources (FLDNR) IDB PID#: AS0471 SETTING CLASSIFICATION: Concrete sea wall OPUS PID: LATITUDE: 29° 54.3' N ( 29.90500) LONGITUDE: 84° 25.0' W ( -84.41670) The bench mark is a disk set flush in the sea wall on the north side of the marina, 18 m (59 ft) south of the dock, and 7.62 m (25.0 ft) west of the SW corner of the Tackle Shop.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 Station ID: 8728288 PUBLICATION DATE: 05/12/2004 Name: ALLIGATOR POINT FL NOAA Chart: 11405 Latitude: 29° 54.2' N ( 29.90330) USGS Quad: ST. TERESA BEACH Longitude: 84° 24.8' W ( -84.41330) T I D A L D A T U M S Tidal datums at ALLIGATOR POINT based on: LENGTH OF SERIES: 2 MONTHS TIME PERIOD: October 1975 - November 1975 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8728229 SHELL POINT, WALKER CREEK Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 0.850 MEAN HIGH WATER MHW = 0.777 MEAN TIDE LEVEL MTL = 0.482 North American Vertical Datum NAVD88 = 0.467 MEAN SEA LEVEL MSL = 0.452 MEAN LOW WATER MLW = 0.186 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 290841 AA 1 1975 1.602 0.825 290841 AA 2 1975 1.933 1.156 290841 AA 4 1975 1.579 0.802 290841 AA 5 1975 1.621 0.844
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 Station ID: 8728288 PUBLICATION DATE: 05/12/2004 Name: ALLIGATOR POINT FL NOAA Chart: 11405 Latitude: 29° 54.2' N ( 29.90330) USGS Quad: ST. TERESA BEACH Longitude: 84° 24.8' W ( -84.41330) D E F I N I T I O N S Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal Datum Epoch. It pertains to local mean sea level and should not be confused with the fixed datums of North American Vertical Datum of 1988 (NAVD88). NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum constraint adjustment of Canadian/Mexican/United States leveling observations. Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as the single initial constraint. NAVD88 replaces NGVD29 as the national standard geodetic reference for heights. Bench mark elevations relative to NAVD88 are available from NGS through the World Wide Web at National Geodetic Survey. NGVD29 is a fixed datum adopted as a national standard geodetic reference for heights but is now considered superseded. NGVD29 is sometimes referred to as Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological Survey Topographic Quads. NGVD29 was originally derived from a general adjustment of the first-order leveling networks of the U.S. and Canada after holding mean sea level observed at 26 long term tide stations as fixed. Numerous local and wide-spread adjustments have been made since establishment in 1929. Bench mark elevations relative to NGVD29 are available from the National Geodetic Survey (NGS) data base via the World Wide Web at National Geodetic Survey. NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to local MSL and other tidal datums may not be consistent from one location to another. The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique identifiers for bench marks in the tidal and geodetic databases, respectively. Each bench mark in either database has a single, unique VM# and/or PID# assigned. Where both VM# and PID# are indicated, both tidal and geodetic elevations are available for the bench mark listed. The NGS's Integrated Data Base (IDB PID) provides geodetic datum based on traditionally leveled and bluebooked ties to the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/. The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/. The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred to MLLW only when two or more of the bench marks listed have NAVD88 elevations. The NAVD88 elevation relationship shown in the table is derived from an average of several bench mark elevations relative to tide station datum. As a result of this averaging, NAVD88 bench mark elevations computed indirectly from the tidal datums elevation table may differ slightly from NAVD88 elevations listed for each bench mark in the NGS database.