Superseded Bench Mark Sheet for 8725383, CAPTIVA ISLAND (SO. END) 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:  09/13/1983
Station ID: 8725383                                SUPERCEDED DATE:   04/21/2003
Name:       CAPTIVA ISLAND, SOUTH END, GULF OF MEXICO         
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 28.7' N
USGS Quad:  WULFERT                                Longitude:        82° 11.0' W


To reach the tidal bench marks from Punta Rassa, go SW over the toll bridge to
Sanibel Island, and continue west from the town of Sanibel to the bridge over
Blind Pass connnecting Sanibel Island to Captiva Island.  The bench marks are on
Sanibel Island and Captiva Island along the road leading from the town of
Sanibel to the bridge over Blind Pass.  The staff was on the Gulf of Mexico on
the west side of the south end of Captiva Island.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1 1965

MONUMENTATION:           Survey Disk                               VM#:     7315
AGENCY:                                                            PID#:  AG1761
SETTING CLASSIFICATION:  Concrete Base of Rafter


The bench mark is set in top of the SW corner of the west one of 5 concrete
bases which support rafters of the Castaway Motel and Novelty Shop, 45 feet
(13.7 m) east of the centerline of the highway, 7.7 feet (2.3 m) SW of the SW
corner of the motel office at the Novelty Shop, and 1.5 feet (0.5 m) SSE of the
SW corner of the sidewalk along the south side of the building and level with
the highway.



                         BENCH MARK STAMPING:  NO 2 1965

MONUMENTATION:           Survey Disk                               VM#:     7316
AGENCY:                                                            PID#:  AG1764
SETTING CLASSIFICATION:  Bridge Abutment


The bench mark is set in the top of the NW abutment of the bridge over Blind
Pass, between Sanibel and Captiva Islands, 23 feet (7.0 m) SW of the centerline
of the highway about 1.0 foot (0.3 m) from the edge of the foundation and 4 feet
(1.2 m) lower than the bridge floor.

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

                                                   PUBLICATION DATE:  09/13/1983
Station ID: 8725383                                SUPERCEDED DATE:   04/21/2003
Name:       CAPTIVA ISLAND, SOUTH END, GULF OF MEXICO         
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 28.7' N
USGS Quad:  WULFERT                                Longitude:        82° 11.0' W


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


                         BENCH MARK STAMPING:  Y 242

MONUMENTATION:           Survey Disk                               VM#:     7317
AGENCY:                                                            PID#:  AG1762
SETTING CLASSIFICATION:  Bridge Abutment


The bench mark is set in the top of the SW end of the SE concrete abutment of
the bridge over Blind Pass between Captiva and Sanibel Island, 18.5 feet (5.6 m)
SW of the centerline of the highway and level with the road.



                         BENCH MARK STAMPING:  X 241 1965

MONUMENTATION:           Survey Disk                               VM#:     7318
AGENCY:                                                            PID#:  AG1760
SETTING CLASSIFICATION:  Copper Clad Rod


The bench mark is 0.05 miles (0.08 km) south of the Castaway Hotel on the inside
of a long curve, 44.8 feet (13.7 m) east of the centerline of the highway, 24
feet (7.3 m) south of the stump of a tree that projects 7 feet (2.1 m) and 1.5
feet (0.5 m) north of power pole #477.  The bench mark is set on top of a copper
rod driven 58.5 feet (17.8 m) and protected by a 4-inch iron pipe and level with
the highway flush with the ground.

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

                                                   PUBLICATION DATE:  09/13/1983
Station ID: 8725383                                SUPERCEDED DATE:   04/21/2003
Name:       CAPTIVA ISLAND, SOUTH END, GULF OF MEXICO         
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 28.7' N
USGS Quad:  WULFERT                                Longitude:        82° 11.0' W


                            T I D A L   D A T U M S 


Tidal datums at CAPTIVA ISLAND, SOUTH END, GULF OF MEXICO based on:

     LENGTH OF SERIES:      11 MONTHS
     TIME PERIOD:           APRIL 1965 - MARCH 1966
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8725110 NAPLES


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

     HIGHEST OBSERVED WATER LEVEL (09/09/1965)         =   4.01
     MEAN HIGHER HIGH WATER                     MHHW   =   2.46
     MEAN HIGH WATER                            MHW    =   2.21
     MEAN TIDE LEVEL                            MTL    =   1.36
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   0.94
     MEAN LOW WATER                             MLW    =   0.52
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (02/04/1966)         =  -1.99

   * NGVD reference based on adjustment of 1966 and NOS levels of1965. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 1 1965                                   5.37      3.16
     NO 2 1965                                   7.47      5.26
     Y 242                                      10.58      8.37
     X 241 1965                                  3.65      1.44


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

                                                   PUBLICATION DATE:  09/13/1983
Station ID: 8725383                                SUPERCEDED DATE:   04/21/2003
Name:       CAPTIVA ISLAND, SOUTH END, GULF OF MEXICO         
            FLORIDA
NOAA Chart: 11426                                  Latitude:         26° 28.7' N
USGS Quad:  WULFERT                                Longitude:        82° 11.0' 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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