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Bench Mark Sheet for 8723999, SOMBRERO KEY LIGHTHOUSE 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 8723999                         PUBLICATION DATE:  05/12/2004
Name:       SOMBRERO KEY LIGHTHOUSE                           
            FL
NOAA Chart: 11449                           Latitude:   24° 37.6' N (  24.62670)
USGS Quad:  MARATHON                        Longitude:  81°  6.7' W ( -81.11170)


To reach the tidal bench marks from the east end of Seven Mile Bridge at Knight
Key, proceed SSE for 9.0 km (5.6 statute mi) to Sombrero Key Lighthouse.  The
lighthouse is an octagonal steel skeleton tower on pile foundation.  The bench
marks are located on the lighthouse structure.  The tide gage and staff were
also located on the lighthouse structure just east of the landing platform.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1
                         DESIGNATION:          872 3999 TIDAL 1

MONUMENTATION:           Bolt                                  VM#:         6300
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Lighthouse structure                  OPUS PID:        
LATITUDE:   24° 37.6' N (  24.62670)          LONGITUDE:  81°  6.7' W ( -81.11170)


The primary bench mark is the high point of the northern nut on the westernmost
stud at the first leg joint clockwise from the landing platform, 8.63 m (28.3
ft) ENE of bench mark NO 4 X, and 0.3 m (1 ft) above the landing platform.



                         BENCH MARK STAMPING:  NO 2
                         DESIGNATION:          872 3999 TIDAL 2

MONUMENTATION:           Bolt                                  VM#:         6301
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Lighthouse structure                  OPUS PID:        
LATITUDE:   24° 37.6' N (  24.62670)          LONGITUDE:  81°  6.7' W ( -81.11170)


The bench mark is the high point of the eastern nut on the SW stud at the first
leg joint counter-clockwise from the landing platform, 8.38 m (27.5 ft) north of
bench mark NO 4 X, 6.49 m (21.3 ft) west of bench mark NO 1, and 0.3 m (1 ft)
above the landing platform.

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

                                                                                
Station ID: 8723999                         PUBLICATION DATE:  05/12/2004
Name:       SOMBRERO KEY LIGHTHOUSE                           
            FL
NOAA Chart: 11449                           Latitude:   24° 37.6' N (  24.62670)
USGS Quad:  MARATHON                        Longitude:  81°  6.7' W ( -81.11170)


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


                         BENCH MARK STAMPING:  NO 3
                         DESIGNATION:          872 3999 TIDAL 3

MONUMENTATION:           Bolt                                  VM#:         6302
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Lighthouse structure                  OPUS PID:        
LATITUDE:   24° 37.6' N (  24.62670)          LONGITUDE:  81°  6.7' W ( -81.11170)


The bench mark is the high point of the western nut on the NE stud at the second
leg joint counter-clockwise from the landing platform, 5.94 m (19.5 ft) west of
bench mark NO 2, and 0.3 m (1 ft) above the landing platform.



                         BENCH MARK STAMPING:  NO 4X
                         DESIGNATION:          872 3999 TIDAL 4X

MONUMENTATION:           Bolt                                  VM#:         6303
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Lighthouse structure                  OPUS PID:        
LATITUDE:   24° 37.6' N (  24.62670)          LONGITUDE:  81°  6.7' W ( -81.11170)


The bench mark is the north end head of the most easterly pin at the center leg
joint, 8.26 m (27.1 ft) SE of bench mark NO 3, and 6 cm (0.2 ft) above the
landing platform.

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

                                                                                
Station ID: 8723999                         PUBLICATION DATE:  05/12/2004
Name:       SOMBRERO KEY LIGHTHOUSE                           
            FL
NOAA Chart: 11449                           Latitude:   24° 37.6' N (  24.62670)
USGS Quad:  MARATHON                        Longitude:  81°  6.7' W ( -81.11170)


                            T I D A L   D A T U M S 


Tidal datums at SOMBRERO KEY LIGHTHOUSE based on:

     LENGTH OF SERIES:      8 MONTHS
     TIME PERIOD:           April 1971 - November 1971
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8723747 TAVERNIER HAWK CHANNEL


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.625
     MEAN HIGH WATER                            MHW    =  0.549
     MEAN SEA LEVEL                             MSL    =  0.308
     MEAN TIDE LEVEL                            MTL    =  0.305
     MEAN LOW WATER                             MLW    =  0.060
     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                                        5.029    4.480
     NO 2                                        5.057    4.508
     NO 3                                        5.060    4.511
     NO 4X                                       4.830    4.281


Foot Notes:

Bench mark NO 4X is based on one differential leveling connection and does not
meet the quality control standards of the NOS. Therefore, caution should be used
when deriving elevations for this mark.

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

                                                                                
Station ID: 8723999                         PUBLICATION DATE:  05/12/2004
Name:       SOMBRERO KEY LIGHTHOUSE                           
            FL
NOAA Chart: 11449                           Latitude:   24° 37.6' N (  24.62670)
USGS Quad:  MARATHON                        Longitude:  81°  6.7' W ( -81.11170)


                             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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Products available at 8723999 SOMBRERO KEY LIGHTHOUSE, FL

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