Superseded Bench Mark Sheet for 8727359, SHELL ISLAND, CRYSTAL RIVER FL

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                   PUBLICATION DATE:  08/23/1984
Station ID: 8727359                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL ISLAND, CRYSTAL RIVER                       
            FLORIDA
NOAA Chart: 11408                                  Latitude:         28° 55.4' N
USGS Quad:  RED LEVEL                              Longitude:        82° 41.5' W


To reach the tidal bench marks proceed to boat ramp at the west end of State
Route 44, Fort Island Beach, then continue by boat 1 mile (1.6 km) to the east
end of Shell Island at the mouth of Crystal River.  The bench marks are located
around the island and the tide gage and staff were located on a 4x4 foot (1x1 m)
platform in Crystal River at the north end of Shell Island.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  7359 B 1978

MONUMENTATION:           Survey Disk                               VM#:     8173
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Steel Rod


The bench mark is at the north end of Shell Island, 40.7 feet (12.4 m) west of a
1.2 foot (0.4 m) diameter twin oak tree, 9.3 feet (2.8 m) SE of another 1.2 foot
(0.4 m) diameter twin oak tree, and 3.8 feet (1.2 m) east of a witness post. 
The bench mark is crimped to a steel rod driven 24 feet (7 m) to refusal and
encased in a PVC pipe and concrete kickblock.



                         BENCH MARK STAMPING:  7359 C 1979

MONUMENTATION:           Survey Disk                               VM#:     8174
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Steel Rod


The bench mark is at the north end of Shell Island, 200 feet (61 m) NW of Bench
Mark EDE 3 1934, 32 foot (10 m) north of the north edge of a sink hole, 13.8
feet (4.2 m) east of a 2.0 foot (0.6 m) diameter white oak tree, 4.0 feet (1.2
m) NE of a 1.3 feet (0.4 m) diameter cabbage palm, and 2.5 feet (0.8 m) NE of a
witness sign.  The bench mark is crimped to a steel rod driven 24 feet (7 m)
substantial residence, and encased in a PVC pipe pipe and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                   PUBLICATION DATE:  08/23/1984
Station ID: 8727359                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL ISLAND, CRYSTAL RIVER                       
            FLORIDA
NOAA Chart: 11408                                  Latitude:         28° 55.4' N
USGS Quad:  RED LEVEL                              Longitude:        82° 41.5' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  SHELL POINT 1857, 1910, 1934

MONUMENTATION:           Survey Disk                               VM#:     8175
AGENCY:                                                            PID#:  AL0960
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in the top of a concrete monument at the SW end of Shell
Island, 48 feet (15 m) west of twin palmettos, 44 feet (13 m) NE of offshore
edge of grass in water at the point, 16 feet (5 m) west of the centerline of a
cluster of several palmettos, and 8 feet (2 m) NE of the waters edge.



                         BENCH MARK STAMPING:  SHELL POINT NO 1 1934

MONUMENTATION:           Survey Disk                               VM#:     8176
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in the top of a square concrete monument, 121.2 feet (36.9
m) NNE of Bench Mark SHELL POINT 1857, 1910, 1934, 22 feet (7 m) inshore from
the waters edge, and 6 feet (2 m) east of the offshore edge of treeline.



                         BENCH MARK STAMPING:  SHELL POINT NO 2 1934

MONUMENTATION:           Survey Disk                               VM#:     8177
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Monument


The bench mark is set in the top of a square concrete monument at the west end
of a dense growth of brush on the south side of the island, 94.3 feet (28.7 m)
ESE of Bench Mark SHELL POINT 1857, 1910, 1934, 44 feet (13 m) east of twin
palmettos, and 21 feet (6 m) north of the waters edge.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                   PUBLICATION DATE:  08/23/1984
Station ID: 8727359                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL ISLAND, CRYSTAL RIVER                       
            FLORIDA
NOAA Chart: 11408                                  Latitude:         28° 55.4' N
USGS Quad:  RED LEVEL                              Longitude:        82° 41.5' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  EDE 3 1955

MONUMENTATION:           Survey Disk                               VM#:     8178
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Post


The bench mark is at the north end of Shell Island, 213.0 feet (64.9 m) SE of
Bench Mark 7359 B 1978, 11.9 feet (3.6 m) east of the NE corner of a tin shed,
and 1.5 feet (0.5 m) north of a witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                   PUBLICATION DATE:  08/23/1984
Station ID: 8727359                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL ISLAND, CRYSTAL RIVER                       
            FLORIDA
NOAA Chart: 11408                                  Latitude:         28° 55.4' N
USGS Quad:  RED LEVEL                              Longitude:        82° 41.5' W


                            T I D A L   D A T U M S 


Tidal datums at SHELL ISLAND, CRYSTAL RIVER based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           SEPTEMBER-NOVEMBER 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8727520 CEDAR KEY


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:

     HIGHEST OBSERVED WATER LEVEL (12/01/1978)         =   4.85
     MEAN HIGHER HIGH WATER                     MHHW   =   3.01
     MEAN HIGH WATER                            MHW    =   2.69
     MEAN TIDE LEVEL                            MTL    =   1.53
     MEAN LOW WATER                             MLW    =   0.37
     MEAN LOWER LOW WATER                       MLLW   =   0.00

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     7359 B 1978                                12.95     10.26
     7359 C 1979                                 4.35      1.66
     SHELL POINT 1857, 1910, 1934                3.32      0.63
     SHELL POINT NO 1 1934                       4.40      1.71
     SHELL POINT NO 2 1934                       3.94      1.25
     EDE 3 1955                                 10.85      8.16


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                   PUBLICATION DATE:  08/23/1984
Station ID: 8727359                                SUPERCEDED DATE:   04/21/2003
Name:       SHELL ISLAND, CRYSTAL RIVER                       
            FLORIDA
NOAA Chart: 11408                                  Latitude:         28° 55.4' N
USGS Quad:  RED LEVEL                              Longitude:        82° 41.5' W


                             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 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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