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Bench Mark Sheet for 8723912, TOMS HARBOR CUT 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Superseded Epoch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Small blue map location marker Unpublished bench mark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  4

                                                                                
Station ID: 8723912                         PUBLICATION DATE:  01/23/2004
Name:       TOM'S HARBOR CUT                                  
            FL
NOAA Chart: 11449                           Latitude:   24° 47.0' N (  24.78330)
USGS Quad:  GRASSY KEY                      Longitude:  80° 54.4' W ( -80.90670)


To reach the tidal bench marks from the post office at Layton, Florida, proceed
SW on U.S. Highway 1 for 10.3 km (6.4 mi).  The bench marks are located in the
area along U.S. Highway 1 on Bridge #22.  The tide gage and staff were located
on the NE corner of Bridge #22.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1 1975
                         DESIGNATION:          872 3912 TIDAL 1

MONUMENTATION:           Tidal Station disk                    VM#:         6255
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete wing wall                    OPUS PID:        
LATITUDE:   24° 47.0' N (  24.78330)          LONGITUDE:  80° 54.4' W ( -80.90670)


The primary bench mark is a disk set flush in the top of the north wing wall at
the NE end of Bridge #22, 18.41 m (60.4 ft) NE of a metal guard for the aqueduct
pipe line, 7.44 m (24.4 ft) SE of the centerline of the highway, and 3.47 m
(11.4 ft) WSW of the NE end of the concrete bridge guardrail. 



                         BENCH MARK STAMPING:  NO 2 1975
                         DESIGNATION:          872 3912 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:         6256
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete curb                         OPUS PID:        
LATITUDE:   24° 47.0' N (  24.78330)          LONGITUDE:  80° 54.4' W ( -80.90670)


The bench mark is a disk set flush in the curb of the NE corner of Bridge #22,
10.88 m (35.7 ft) west of bench mark P 278 1966, and 3.60 m (11.8 ft) north of
the centerline of U.S. Highway 1.

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

                                                                                
Station ID: 8723912                         PUBLICATION DATE:  01/23/2004
Name:       TOM'S HARBOR CUT                                  
            FL
NOAA Chart: 11449                           Latitude:   24° 47.0' N (  24.78330)
USGS Quad:  GRASSY KEY                      Longitude:  80° 54.4' W ( -80.90670)


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


                         BENCH MARK STAMPING:  P 278 1966
                         DESIGNATION:          P 278

MONUMENTATION:           Bench Mark disk                       VM#:         6257
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AA0372
SETTING CLASSIFICATION:  Concrete wing wall                    OPUS PID:        
LATITUDE:   24° 47.0' N (  24.78330)          LONGITUDE:  80° 54.4' W ( -80.90670)


The bench mark is a disk set in top of the south concrete wing wall of Bridge
#22, at the SE end of the 0.3 km (0.2 mi) long bridge, 7 m (24 ft) SE of the
centerline of U.S. Highway 1, and 2 m (5 ft) below highway level.

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

                                                                                
Station ID: 8723912                         PUBLICATION DATE:  01/23/2004
Name:       TOM'S HARBOR CUT                                  
            FL
NOAA Chart: 11449                           Latitude:   24° 47.0' N (  24.78330)
USGS Quad:  GRASSY KEY                      Longitude:  80° 54.4' W ( -80.90670)


                            T I D A L   D A T U M S 


Tidal datums at TOM'S HARBOR CUT based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           February 1975 - February 1975
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8724211 BIG PINE KEY VIADUCT


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.230
     MEAN HIGH WATER                            MHW    =  0.165
     MEAN SEA LEVEL                             MSL    =  0.098
     MEAN TIDE LEVEL                            MTL    =  0.094
     MEAN LOW WATER                             MLW    =  0.023
     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 1975                                   2.098    1.933
     NO 2 1975                                   4.637    4.472
     P 278 1966                                  3.250    3.085


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

                                                                                
Station ID: 8723912                         PUBLICATION DATE:  01/23/2004
Name:       TOM'S HARBOR CUT                                  
            FL
NOAA Chart: 11449                           Latitude:   24° 47.0' N (  24.78330)
USGS Quad:  GRASSY KEY                      Longitude:  80° 54.4' W ( -80.90670)


                             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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Revised: 08/08/2018
NOAA / National Ocean Service
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