Superseded Bench Mark Sheet for 8724378, PERKY, SUGARLOAF SOUND FL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Station ID: 8724378                                SUPERCEDED DATE:   04/21/2003
Name:       PERKY, UPPER SUGARLOAF SOUND                      
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 38.9' N
USGS Quad:  SUGARLOAF KEY                          Longitude:        81° 34.2' W


To reach the tidal bench marks from the junction of U.S. Highway 1 and State
Highway 939 in the village of Perky, proceed west on U.S. Highway 1 for 0.05
mile (0.08 km) to the side road on the right, turn right and continue north for
0.4 mile (0.6 km) to buildings, a small airport and a pond.  The bench marks are
located at the pond and observation towers.  The tide gage and staff were
located on a jetty east of the pond.


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


                 PRIMARY BENCH MARK STAMPING:  V 271 1966

MONUMENTATION:           Survey Disk                               VM#:     7048
AGENCY:                                                            PID#:  AA0129
SETTING CLASSIFICATION:  Concrete Foundation


The bench mark is set vertically in the SE face of the south base of an
observation tower which is part of a large frame house, 106 feet (32 m) NE of
the centerline of the private road leading to the airport, and 2 feet (1 m)
above the ground.



                         BENCH MARK STAMPING:  PERKY SW BASE AZ MARK 1935

MONUMENTATION:           Survey Disk                               VM#:     7047
AGENCY:                                                            PID#:  AA0130
SETTING CLASSIFICATION:  Concrete Base


The bench mark is set in the top of the east side of a 4-foot (1 m) square
concrete base supporting the south wooden leg of a 30-foot (9 m) high wooden
tower, about 528 feet (161 m) NW of a frame house with an observation tower, and
about level with the ground.

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

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8724378                                SUPERCEDED DATE:   04/21/2003
Name:       PERKY, UPPER SUGARLOAF SOUND                      
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 38.9' N
USGS Quad:  SUGARLOAF KEY                          Longitude:        81° 34.2' W


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


                         BENCH MARK STAMPING:  NO 1 1974

MONUMENTATION:           Survey Disk                               VM#:     7049
AGENCY:                                                            PID#:  AA0729
SETTING CLASSIFICATION:  Concrete Seawall


The bench mark is set in a concrete seawall, 26.0 feet (7.9 m) SE of the NW
corner of a pond, 26 feet (8 m) NE of the centerline of a road, 23.5 feet (7.2
m) NW of a turn in a road near the SW corner of the pond, and level with the
ground.

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

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8724378                                SUPERCEDED DATE:   04/21/2003
Name:       PERKY, UPPER SUGARLOAF SOUND                      
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 38.9' N
USGS Quad:  SUGARLOAF KEY                          Longitude:        81° 34.2' W


                            T I D A L   D A T U M S 


Tidal datums at PERKY, UPPER SUGARLOAF SOUND based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           APRIL-MAY 1974
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8724580 KEY WEST


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

     HIGHEST OBSERVED WATER LEVEL (05/23/1974)         =   1.39
     MEAN HIGHER HIGH WATER                     MHHW   =   0.59
     MEAN HIGH WATER                            MHW    =   0.44
     MEAN TIDE LEVEL                            MTL    =   0.23
     MEAN LOW WATER                             MLW    =   0.02
     MEAN LOWER LOW WATER                       MLLW   =   0.00
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =  -0.56
     LOWEST  OBSERVED WATER LEVEL (04/12/1974)         =  -0.40

   * NGVD reference based on elevations published in Quad 240814, 1971, and NOS
     leveling of 1982. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     V 271 1966                                  4.94      4.50
     PERKY SW BASE AZ MARK 1935                  1.52      1.08
     NO 1 1974                                   1.65      1.21


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

                                                   PUBLICATION DATE:  07/01/1986
Station ID: 8724378                                SUPERCEDED DATE:   04/21/2003
Name:       PERKY, UPPER SUGARLOAF SOUND                      
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 38.9' N
USGS Quad:  SUGARLOAF KEY                          Longitude:        81° 34.2' 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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