Superseded Bench Mark Sheet for 8724975, BLACKWATER RIVER ENTRANCE FL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:  03/28/1988
Station ID: 8724975                                SUPERCEDED DATE:   04/21/2003
Name:       BLACKWATER RIVER ENTRANCE, BLACKWATER RIVER       
            FLORIDA
NOAA Chart: 11429                                  Latitude:         25° 55.9' N
USGS Quad:  ROYAL PALM HAMMOCK                     Longitude:        81° 35.8' W


To reach the tidal bench marks from Goodland proceed by boat in the southerly
direction for about 2.5 statute miles (4.0 km) to the southern tip of Tripod Key
and then continue NE for about 4 statute miles (6 km) to the entrance of
Blackwater River.  The bench marks are located on the east shore of the river,
about 0.3 mile (0.5 km) north of the entrance.  The tide gage and staff were
located in the river west of Bench Mark 4975 A 1978, on a free standing
structure, about 15 feet (5 m) offshore.


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


                 PRIMARY BENCH MARK STAMPING:  4975 A 1978

MONUMENTATION:           Survey Disk                               VM#:     9748
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 25 feet (8 m) west of a 0.8 foot (0.2 m) diameter mangrove
tree, 23.0 feet (7.0 m) SSW of Bench Mark 4975 B 1978, 7 feet (2 m) east of the
approximate high water line, and 1.1 feet (0.3 m) NW of a witness post.  The
bench mark is 0.8 foot (0.2 m) above the ground, crimped to a galvanized steel
rod driven 21 feet (6 m) to refusal, and encased by a 4-inch steel pipe.



                         BENCH MARK STAMPING:  4975 B 1978

MONUMENTATION:           Survey Disk                               VM#:     9749
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is about 50 feet (15 m) WNW of a small creek, 33 feet (10 m) WSW
of Bench Mark 4975 C 1978, 17 feet (5 m) east of the approximate high water
line, and 1.2 feet (0.4 m) SW of a witness post.  The bench mark is 0.8 foot
(0.2 m) above the ground, crimped to a galvanized steel rod driven 20 feet (6 m)
to refusal, and encased by a 4-inch steel pipe.

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

                                                   PUBLICATION DATE:  03/28/1988
Station ID: 8724975                                SUPERCEDED DATE:   04/21/2003
Name:       BLACKWATER RIVER ENTRANCE, BLACKWATER RIVER       
            FLORIDA
NOAA Chart: 11429                                  Latitude:         25° 55.9' N
USGS Quad:  ROYAL PALM HAMMOCK                     Longitude:        81° 35.8' W


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


                         BENCH MARK STAMPING:  4975 C 1978

MONUMENTATION:           Survey Disk                               VM#:     9750
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is about 50 feet (15 m) east of the approximate high water line,
33 feet (10 m) SE of Bench Mark 4975 D 1978, 20 feet (6 m) NW of a small creek,
and 1.0 foot (0.3 m) NW of a witness post.  The bench mark is 0.8 foot (0.2 m)
above the ground, crimped to a galvanized steel rod driven 23 feet (7 m) to
refusal, and encased by a 4-inch steel pipe.



                         BENCH MARK STAMPING:  4975 D 1978

MONUMENTATION:           Survey Disk                               VM#:     9751
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 90 feet (27 m) south of Bench Mark 4975 E 1978, 30 feet (9 m)
east of the approximate high water line, and 0.8 foot (0.2 m) west of a new
witness post.  The bench mark is 0.6 foot (0.2 m) above the ground, crimped to a
galvanized steel rod driven 36 feet (11 m) to refusal and encased by a 4-inch
steel pipe.



                         BENCH MARK STAMPING:  4975 E 1978

MONUMENTATION:           Survey Disk                               VM#:     9752
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is 20 feet (6 m) east of the approximate high water line, and 1.3
feet (0.4 m) WSW of a witness post.  The bench mark is 0.5 foot (0.2 m) above
the ground crimped to a galvanized steel rod driven 40 feet (12 m) to refusal,
and encased by a 4-inch steel pipe.

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

                                                   PUBLICATION DATE:  03/28/1988
Station ID: 8724975                                SUPERCEDED DATE:   04/21/2003
Name:       BLACKWATER RIVER ENTRANCE, BLACKWATER RIVER       
            FLORIDA
NOAA Chart: 11429                                  Latitude:         25° 55.9' N
USGS Quad:  ROYAL PALM HAMMOCK                     Longitude:        81° 35.8' W


                            T I D A L   D A T U M S 


Tidal datums at BLACKWATER RIVER ENTRANCE, BLACKWATER RIVER based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           JANUARY, MARCH, APRIL 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8724967 MARCO ISLAND


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

     HIGHEST OBSERVED WATER LEVEL (05/04/1978)         =   4.17
     MEAN HIGHER HIGH WATER                     MHHW   =   3.24
     MEAN HIGH WATER                            MHW    =   2.99
     MEAN TIDE LEVEL                            MTL    =   1.70
     MEAN LOW WATER                             MLW    =   0.41
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (03/18/1978)         =  -1.11



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     4975 A 1978                                 4.93      1.94
     4975 B 1978                                 5.34      2.35
     4975 C 1978                                 4.44      1.45
     4975 D 1978                                 4.38      1.39
     4975 E 1978                                 4.91      1.92


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

                                                   PUBLICATION DATE:  03/28/1988
Station ID: 8724975                                SUPERCEDED DATE:   04/21/2003
Name:       BLACKWATER RIVER ENTRANCE, BLACKWATER RIVER       
            FLORIDA
NOAA Chart: 11429                                  Latitude:         25° 55.9' N
USGS Quad:  ROYAL PALM HAMMOCK                     Longitude:        81° 35.8' 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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