Superseded Bench Mark Sheet for 8723439, BILLYS POINT, ELLIOTT KEY FL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  4

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8723439                                SUPERCEDED DATE:   04/21/2003
Name:       BILLYS POINT, ELLIOTT KEY, BISCAYNE BAY           
            FLORIDA
NOAA Chart: 11462                                  Latitude:         25° 24.9' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 12.6' W


To reach the tidal bench marks by boat from Elliott Key Harbor, proceed 3 miles
(5 km) SW to an abandoned wooden dock located 0.75 mile (1.21 km) SSE of Billys
Point.  The bench marks are located along an east-west trail and in the vicinity
of the abandoned wooden dock.  The tide gage and staff were located off the
south side of the wooden dock.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1 1974

MONUMENTATION:           Survey Disk                               VM#:     5851
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Outcropping Coral


The bench mark is set flush in outcropping coral, 95 feet (29 m) inshore from
the east end of the abandoned wooden dock, 54 feet (16 m) south of Bench Mark NO
4 1974, 30.1 feet (9 m) SSW of Bench Mark NO 2 1974, 28 feet (8 m) south of an
east-west trail, and 2.5 feet (0.8 m) south of a witness post.



                         BENCH MARK STAMPING:  NO 2 1974

MONUMENTATION:           Survey Disk                               VM#:     5852
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Outcropping Coral


The bench mark is set flush in outcropping coral, 99 feet (30 m) east of the
east end of the dock, 62.3 feet (19.0 m) east of Bench Mark NO 5 1974, 38 feet
(12 m) SSE of Bench Mark NO 4 1974, 30.1 feet (9.2 m) NNE of Bench Mark NO 1
1974, and 3.7 feet (1.1 m) SW of a witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  4

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8723439                                SUPERCEDED DATE:   04/21/2003
Name:       BILLYS POINT, ELLIOTT KEY, BISCAYNE BAY           
            FLORIDA
NOAA Chart: 11462                                  Latitude:         25° 24.9' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 12.6' W


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


                         BENCH MARK STAMPING:  NO 3 1974

MONUMENTATION:           Survey Disk                               VM#:     5853
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Outcropping Coral


The bench mark is set flush in outcropping coral, in the center of the east-west
trail, 171 feet (52 m) east of the east end of the dock, 72.6 feet (22.1 m) west
of Bench Mark NO 2 1974, and 2.3 feet (0.7 m) SSW of a witness post.



                         BENCH MARK STAMPING:  NO 4 1974

MONUMENTATION:           Survey Disk                               VM#:     5854
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Outcropping Coral


The bench mark is set flush in outcropping coral, 90 feet (27 m) inshore from
the dock, 54 feet (16 m) WNW of Bench Mark NO 1 1974, 37 feet (11 m) NW of Bench
Mark NO 2 1974, 27 feet (8 m) north of the east-west trail, and 3.5 feet (1.1 m)
west of a witness post.



                         BENCH MARK STAMPING:  NO 5 1974

MONUMENTATION:           Survey Disk                               VM#:     5855
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Outcropping Coral


The bench mark is set flush in outcropping coral, in the center of the east-west
trail, 61.7 feet (18.8 m) west of Bench Mark NO 2 1974, 36.5 feet (11.1 m) east
of the east end of the dock, and 8.0 feet (2.4 m) NNW of a witness post.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  4

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8723439                                SUPERCEDED DATE:   04/21/2003
Name:       BILLYS POINT, ELLIOTT KEY, BISCAYNE BAY           
            FLORIDA
NOAA Chart: 11462                                  Latitude:         25° 24.9' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 12.6' W


                            T I D A L   D A T U M S 


Tidal datums at BILLYS POINT, 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 NO 3


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

     HIGHEST OBSERVED WATER LEVEL (07/16/1974)         =   1.95
     MEAN HIGHER HIGH WATER                     MHHW   =   1.62
     MEAN HIGH WATER                            MHW    =   1.55
     MEAN TIDE LEVEL                            MTL    =   0.82
     MEAN LOW WATER                             MLW    =   0.09
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (06/27/1974)         =  -0.35



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 1 1974                                   3.07      1.52
     NO 2 1974                                   3.06      1.51
     NO 3 1974                                   4.41      2.86
     NO 4 1974                                   2.29      0.74
     NO 5 1974                                   2.44      0.89


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

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8723439                                SUPERCEDED DATE:   04/21/2003
Name:       BILLYS POINT, ELLIOTT KEY, BISCAYNE BAY           
            FLORIDA
NOAA Chart: 11462                                  Latitude:         25° 24.9' N
USGS Quad:  ELLIOTT KEY                            Longitude:        80° 12.6' 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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