Bench Mark Sheet for 8724438, SHARK KEY FL

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 8724438                         PUBLICATION DATE:  09/21/2005
Name:       SHARK KEY                                         
            FL
NOAA Chart: 11445                           Latitude:   24° 36.2' N (  24.60330)
USGS Quad:  BOCA CHICA KEY                  Longitude:  81° 38.7' W ( -81.64500)


To reach the tidal bench marks from the Catholic Church in Key West, proceed
17.0 km (10.6 mi) NE on U.S. Highway 1 to the NE to the west end of the bridge
over Shark Channel.  The bench marks are located in the wingwall of the old
highway bridge, how used as a fishing pier.  The tide gage and staff were
located at the north end of the west wingwall.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1 1973
                         DESIGNATION:          872 4438 TIDAL 1

MONUMENTATION:           Tidal Station disk                    VM#:        11095
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0986
SETTING CLASSIFICATION:  Concrete wing wall                    OPUS PID:        
LATITUDE:   24° 36.2' N (  24.60330)          LONGITUDE:  81° 38.7' W ( -81.64500)


The primary bench mark is a disk set in the wing wall at the SW end of the old
highway bridge, underneath the new bridge, 9 m (30 ft) NW of the NW edge of the
old bridge, and 3 m (10 ft) below U.S. Highway 1.  NOTE:  A level rod will not
fit on the mark and a tape is needed for leveling.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8724438                         PUBLICATION DATE:  09/21/2005
Name:       SHARK KEY                                         
            FL
NOAA Chart: 11445                           Latitude:   24° 36.2' N (  24.60330)
USGS Quad:  BOCA CHICA KEY                  Longitude:  81° 38.7' W ( -81.64500)


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


                         BENCH MARK STAMPING:  N 271 1966
                         DESIGNATION:          N 271
                         ALIAS:                872 4438 TIDAL

MONUMENTATION:           Bench Mark disk                       VM#:        11094
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AA0112
SETTING CLASSIFICATION:  Concrete bridge curb                  OPUS PID:        
LATITUDE:   24° 36.2' N (  24.60330)          LONGITUDE:  81° 38.5' W ( -81.64170)


The bench mark is a disk set in the north curb at the SW end of the old highway
bridge, 4 m (13 ft) NW of the centerline of the old highway, and 0.3 m (1.0 ft)
above the pavement level.



                         BENCH MARK STAMPING:  NO 2 1973
                         DESIGNATION:          872 4438 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:        11096
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0988
SETTING CLASSIFICATION:  Concrete curb                         OPUS PID:        
LATITUDE:   24° 36.2' N (  24.60330)          LONGITUDE:  81° 38.7' W ( -81.64500)


The bench mark is a disk set in the south curb at the SW end of the old highway
bridge, 0.3 m (1.0 ft) below U.S. Highway 1.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8724438                         PUBLICATION DATE:  09/21/2005
Name:       SHARK KEY                                         
            FL
NOAA Chart: 11445                           Latitude:   24° 36.2' N (  24.60330)
USGS Quad:  BOCA CHICA KEY                  Longitude:  81° 38.7' W ( -81.64500)


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


                         BENCH MARK STAMPING:  NO 3 1973
                         DESIGNATION:          872 4438 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:        11097
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0987
SETTING CLASSIFICATION:  Concrete wing wall                    OPUS PID:        
LATITUDE:   24° 36.2' N (  24.60330)          LONGITUDE:  81° 38.7' W ( -81.64500)


The bench mark is a disk set in the wing wall at the SW end of the old highway
bridge, 3.93 m (12.9 ft) SE of the SW end of the SE bridge guardrail, and 2 m (6
ft) below U.S. Highway 1.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8724438                         PUBLICATION DATE:  09/21/2005
Name:       SHARK KEY                                         
            FL
NOAA Chart: 11445                           Latitude:   24° 36.2' N (  24.60330)
USGS Quad:  BOCA CHICA KEY                  Longitude:  81° 38.7' W ( -81.64500)


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


                         BENCH MARK STAMPING:  T 70 RESET 1938
                         DESIGNATION:          T 70 RESET
                         ALIAS:                872 4438 TIDAL

MONUMENTATION:           Bench Mark disk                       VM#:        11098
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AA0113
SETTING CLASSIFICATION:  Concrete wing wall                    OPUS PID:        
LATITUDE:   24° 36.4' N (  24.60670)          LONGITUDE:  81° 38.2' W ( -81.63670)


The bench mark is a disk set in the SE concrete wing wall at the NE end of the
old highway bridge, 5 m (16 ft) SE of the centerline of the old highway, and 1 m
(3 ft) below the level of the old bridge.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8724438                         PUBLICATION DATE:  09/21/2005
Name:       SHARK KEY                                         
            FL
NOAA Chart: 11445                           Latitude:   24° 36.2' N (  24.60330)
USGS Quad:  BOCA CHICA KEY                  Longitude:  81° 38.7' W ( -81.64500)


                            T I D A L   D A T U M S 


Tidal datums at SHARK KEY based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           March 1974 - May 1974
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8724580 KEY WEST


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

     North American Vertical Datum              NAVD88 =  0.356
     MEAN HIGHER HIGH WATER                     MHHW   =  0.307
     MEAN HIGH WATER                            MHW    =  0.239
     MEAN SEA LEVEL                             MSL    =  0.155
     MEAN TIDE LEVEL                            MTL    =  0.136
     MEAN LOW WATER                             MLW    =  0.032
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     NO 1 1973                                   1.477    1.238
     N 271 1966                                  4.219    3.980
     NO 2 1973                                   4.217    3.978
     NO 3 1973                                   2.441    2.202
     T 70 RESET 1938                             3.596    3.357


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8724438                         PUBLICATION DATE:  09/21/2005
Name:       SHARK KEY                                         
            FL
NOAA Chart: 11445                           Latitude:   24° 36.2' N (  24.60330)
USGS Quad:  BOCA CHICA KEY                  Longitude:  81° 38.7' W ( -81.64500)


                             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 NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.

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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