Superseded Bench Mark Sheet for 8723409, ELLIOTT KEY HARBOR, ELLIOTT KEY FL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:  09/29/1989
Station ID: 8723409                                SUPERCEDED DATE:   04/21/2003
Name:       ELLIOTT KEY HARBOR, ELLIOTT KEY, BISCAYNE BAY     
            FLORIDA
NOAA Chart: 11463                                  Latitude:         25° 27.2' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 11.8' W


To reach the tidal bench marks from the intersection of U.S. Highway 1 and Lucy
Street (SW 328th Street) in Florida City, proceed east on Lucy Street for 8.8
miles (14.2 km) to the boat ramp at Biscayne National Park.  Continue east by
boat for 8.7 miles (14.0 km) to the Elliott Key Visitor Center Boat Basin on the
west side of Elliott Key.  The bench marks are in the vicinity of the boat basin
visitor center, and maintenance dock.  The tide gage and staff were on the
maintenance dock south of the basin.


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


                 PRIMARY BENCH MARK STAMPING:  NO 3 1974

MONUMENTATION:           Survey Disk                               VM#:     5837
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Rock Outcrop


The bench mark is set in a rock outcrop east of the boat basin, 135.2 feet (41.2
m) SSE of a light pole at the boat basin, 56.2 feet (17.1 m) east of the
easternmost corner of the south basin, 25.5 feet (7.8 m) ENE of Bench Mark 19,
and 4 feet (1 m) north of a tree.



                         BENCH MARK STAMPING:  3409 F 1987

MONUMENTATION:           Survey Disk                               VM#:     5838
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is set flush in the east corner of a concrete foundation for a
flag pole at the westernmost end of the center of three piers of the boat basin.

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

                                                   PUBLICATION DATE:  09/29/1989
Station ID: 8723409                                SUPERCEDED DATE:   04/21/2003
Name:       ELLIOTT KEY HARBOR, ELLIOTT KEY, BISCAYNE BAY     
            FLORIDA
NOAA Chart: 11463                                  Latitude:         25° 27.2' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 11.8' W


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


                         BENCH MARK STAMPING:  3409 G 1987

MONUMENTATION:           Survey Disk                               VM#:     5839
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Footing


The bench mark is set in the concrete footing at the east end of the maintenance
dock, 14.0 feet (4.3 m) west of the NE corner of the dock, 0.5 foot (0.2 m)
south of the north edge of the dock, and level with the dock.



                         BENCH MARK STAMPING:  3409 H 1987

MONUMENTATION:           Survey Disk                               VM#:     5840
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Stainless Steel Rod


The bench mark is set in the WSW corner of a deck located between the Visitor
Center and the public restroom, 28.5 feet (8.7 m) ENE of the east corner of the
restroom building, 11.7 feet (3.6 m) SSW of the south corner of the Visitor
Center, and 2.0 feet (0.6 m) WSW of the deck corner.  The bench mark is level
with the ground, driven 2 feet (1 m) to refusal, and encased in a PVC pipe with
concrete kickblock.



                         BENCH MARK STAMPING:  3409 J 1987

MONUMENTATION:           Survey Disk                               VM#:     5841
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Step


The bench mark is set in the first step at the SW corner of the generator
building, about 315 feet (96 m) ESE of the maintenance dock, 1.6 feet (0.5 m) SE
of the SW corner of the building, and 0.7 foot (0.2 m) SSW of the west side of
the building.

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

                                                   PUBLICATION DATE:  09/29/1989
Station ID: 8723409                                SUPERCEDED DATE:   04/21/2003
Name:       ELLIOTT KEY HARBOR, ELLIOTT KEY, BISCAYNE BAY     
            FLORIDA
NOAA Chart: 11463                                  Latitude:         25° 27.2' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 11.8' W


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


                         BENCH MARK STAMPING:  19

MONUMENTATION:           Survey Disk                               VM#:     5842
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Rock Outcrop


The bench mark is set in a rock outcrop east of the boat basin, 128.5 feet (39.2
m) SSE of a light pole at the boast basin, 104.8 feet (31.9 m) north of the
northernmost corner of a picnic shelter, 31.4 feet (9.6 m) east of the
easternmost corner of the south basin, and level with the ground.

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

                                                   PUBLICATION DATE:  09/29/1989
Station ID: 8723409                                SUPERCEDED DATE:   04/21/2003
Name:       ELLIOTT KEY HARBOR, ELLIOTT KEY, BISCAYNE BAY     
            FLORIDA
NOAA Chart: 11463                                  Latitude:         25° 27.2' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 11.8' W


                            T I D A L   D A T U M S 


Tidal datums at ELLIOTT KEY HARBOR, ELLIOTT KEY, BISCAYNE BAY based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           JULY 1974
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8723350 RAGGED KEY #3


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

     HIGHEST OBSERVED WATER LEVEL (10/20/1987)         =   2.60
     MEAN HIGHER HIGH WATER                     MHHW   =   1.64
     MEAN HIGH WATER                            MHW    =   1.57
     MEAN TIDE LEVEL                            MTL    =   0.83
     MEAN LOW WATER                             MLW    =   0.09
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (06/27/1974)         =  -0.28



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 3 1974                                   5.74      4.17
     3409 F 1987                                 4.29      2.72
     3409 G 1987                                 4.08      2.51
     3409 H 1987                                 7.50      5.93
     3409 J 1987                                 9.79      8.22
     19                                          5.11      3.54


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

                                                   PUBLICATION DATE:  09/29/1989
Station ID: 8723409                                SUPERCEDED DATE:   04/21/2003
Name:       ELLIOTT KEY HARBOR, ELLIOTT KEY, BISCAYNE BAY     
            FLORIDA
NOAA Chart: 11463                                  Latitude:         25° 27.2' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 11.8' 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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