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Bench Mark Sheet for 8728288, ALLIGATOR POINT FL

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          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.

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Products available at 8728288 ALLIGATOR POINT, FL

Revised: 10/15/2013
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services