Bench Mark Sheet for 8724062, MOLASSES 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Superseded Epoch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Small blue map location marker Unpublished bench mark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  5

                                                                                
Station ID: 8724062                         PUBLICATION DATE:  05/10/2004
Name:       MOLASSES KEY                                      
            FL
NOAA Chart: 11442                           Latitude:   24° 41.0' N (  24.68330)
USGS Quad:  SEVENMILE BRIDGE                Longitude:  81° 11.5' W ( -81.19170)


To reach the tidal bench marks by boat from the west end of the Seven Mile
Bridge on Little Duck Key, proceed 4.0 km (2.2 nm) east to the NW end of the
center of three Keys forming the Molasses Keys Group.  The bench marks are
located at the center key of Molasses Keys.  The tide gage and staff were
located offshore from the Keys on a free standing structure.


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


                 PRIMARY BENCH MARK STAMPING:  TOM 1974
                         DESIGNATION:          872 4062 TOM

MONUMENTATION:           Tidal Station disk                    VM#:         6322
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Coral rock                            OPUS PID:        
LATITUDE:   24° 41.0' N (  24.68330)          LONGITUDE:  81° 11.5' W ( -81.19170)


The primary bench mark is a disk set flush in the coral rock. 24.81 m (81.4 ft)
ENE of bench mark LS, 19.90 m (65.3 ft) ENE of bench mark RON 1974, and 19.05 m
(62.5 ft) SE of the rock ledge.



                         BENCH MARK STAMPING:  MOLASSES KEY 1856 1909 35 NO 2
                         DESIGNATION:          872 4062 MOLASSES KEY

MONUMENTATION:           Reference Mark disk                   VM#:         6320
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   24° 41.0' N (  24.68330)          LONGITUDE:  81° 11.5' W ( -81.19170)


The bench mark is a disk set in the top of a concrete monument located in the
center of Molasses Key, 91 m (297 ft) from the west end of the island, 19.32 m
(63.4 ft) SE of the NW rock ledge, 18 m (59 ft) from the south end of the
island, and 0.12 m (0.4 ft) above ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 8724062                         PUBLICATION DATE:  05/10/2004
Name:       MOLASSES KEY                                      
            FL
NOAA Chart: 11442                           Latitude:   24° 41.0' N (  24.68330)
USGS Quad:  SEVENMILE BRIDGE                Longitude:  81° 11.5' W ( -81.19170)


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


                         BENCH MARK STAMPING:  MAX 1974
                         DESIGNATION:          872 4062 MAX

MONUMENTATION:           Tidal Station disk                    VM#:         6321
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete block embedded into coral rockOPUS PID:        
LATITUDE:   24° 41.0' N (  24.68330)          LONGITUDE:  81° 11.5' W ( -81.19170)


The bench mark is a disk set flush in a concrete block embedded into the coral
rock, 21.73 m (71.3 ft) SSW of bench mark RON 1974, 19.81 m (65.0 ft) NW of the
SE rock ledge, 19.81 m (65.0 ft) SE of the NW rock ledge, and 16.86 m (55.3 ft)
WSW of bench mark LS.



                         BENCH MARK STAMPING:  RON 1974
                         DESIGNATION:          872 4062 RON

MONUMENTATION:           Tidal Station disk                    VM#:         6323
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete block embedded into coral rockOPUS PID:        
LATITUDE:   24° 41.0' N (  24.68330)          LONGITUDE:  81° 11.5' W ( -81.19170)


The bench mark is a disk set flush in a concrete block embedded into the coral
rock, 19.96 m (65.5 ft) west of bench mark TOM 1974, 19.48 m (63.9 ft) NW of
reference mark KEY 1856 1909 35 NO 2, 10.67 m (35.0 ft) SE of the rock ledge,
and 0.15 m (0.5 ft) above ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 8724062                         PUBLICATION DATE:  05/10/2004
Name:       MOLASSES KEY                                      
            FL
NOAA Chart: 11442                           Latitude:   24° 41.0' N (  24.68330)
USGS Quad:  SEVENMILE BRIDGE                Longitude:  81° 11.5' W ( -81.19170)


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


                         BENCH MARK STAMPING:  LS
                         DESIGNATION:          872 4062 LS TIDAL

MONUMENTATION:           Survey disk                           VM#:         6324
AGENCY:                  Buckely Schuh & Jernigan              IDB PID#:        
SETTING CLASSIFICATION:  Concrete post                         OPUS PID:        
LATITUDE:   24° 41.0' N (  24.68330)          LONGITUDE:  81° 11.5' W ( -81.19170)


The bench mark is a disk set in a concrete post, 14.69 m (48.2 ft)  SW of
reference mark MOLASSES KEY 1856 1909 35 NO 2, 14.33 m (47.0 ft) SSE of bench
mark RON 1974, and 1.77 m (5.8 ft) WSW of an 1-inch diameter steel pin driven
into bedrock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 8724062                         PUBLICATION DATE:  05/10/2004
Name:       MOLASSES KEY                                      
            FL
NOAA Chart: 11442                           Latitude:   24° 41.0' N (  24.68330)
USGS Quad:  SEVENMILE BRIDGE                Longitude:  81° 11.5' W ( -81.19170)


                            T I D A L   D A T U M S 


Tidal datums at MOLASSES KEY based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           June 1974 - June 1974
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8724138 BAHIA HONDA KEY


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.436
     MEAN HIGH WATER                            MHW    =  0.361
     MEAN SEA LEVEL                             MSL    =  0.202
     MEAN TIDE LEVEL                            MTL    =  0.199
     MEAN LOW WATER                             MLW    =  0.037
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     TOM 1974                                    0.566    0.205
     MOLASSES KEY 1856 1909 35 NO 2              0.667    0.306
     MAX 1974                                    0.706    0.345
     RON 1974                                    0.724    0.363
     LS                                          0.575    0.214


Foot Notes:

Bench mark LS 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 an elevation for this mark.

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

                                                                                
Station ID: 8724062                         PUBLICATION DATE:  05/10/2004
Name:       MOLASSES KEY                                      
            FL
NOAA Chart: 11442                           Latitude:   24° 41.0' N (  24.68330)
USGS Quad:  SEVENMILE BRIDGE                Longitude:  81° 11.5' W ( -81.19170)


                             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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