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Bench Mark Sheet for 8723933, GRASSY KEY, ATLANTIC SIDE 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 8723933                         PUBLICATION DATE:  12/12/2003
Name:       GRASSY KEY, ATLANTIC SIDE                         
            FL
NOAA Chart: 11449                           Latitude:   24° 45.3' N (  24.75500)
USGS Quad:  GRASSY KEY                      Longitude:  80° 57.5' W ( -80.95830)


To reach the tidal bench marks from the post office in Marathon, proceed NE on
U.S. Highway 1 for 12.7 km (7.9 mi) to the Rainbow Bend Resort. The bench marks
are in the area around the resort.  The tide gage and staff were located on the
resorts pier.


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


                 PRIMARY BENCH MARK STAMPING:  NO 4 1975
                         DESIGNATION:          872 3933 TIDAL 4

MONUMENTATION:           Tidal Station disk                    VM#:         6284
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0861
SETTING CLASSIFICATION:  Concrete pad                          OPUS PID:        
LATITUDE:   24° 45.3' N (  24.75500)          LONGITUDE:  80° 57.5' W ( -80.95830)


The primary bench mark is a disk set in the south corner of a concrete pad,
22.71 m (74.5 ft) SE of the centerline of U.S. Highway 1, 12.98 m (42.6 ft)
south of the north corner of a concrete wall at the north property corner, 10 m
(33 ft) NE of bench mark NO 3 1975, 6.25 m (20.5 ft) NE of the centerline of the
NE entrance drive to the resort, and 0.15 m (0.5 ft) above ground level.



                         BENCH MARK STAMPING:  NO 3 1975
                         DESIGNATION:          872 3933 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:         6283
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0862
SETTING CLASSIFICATION:  Concrete walkway                      OPUS PID:        
LATITUDE:   24° 45.3' N (  24.75500)          LONGITUDE:  80° 57.5' W ( -80.95830)


The bench mark is a disk set in a concrete walkway near the NW entrance to the
apartment building near the north corner of the property, and 1.52 m (5.0 ft)
west of the NW corner of the building.

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

                                                                                
Station ID: 8723933                         PUBLICATION DATE:  12/12/2003
Name:       GRASSY KEY, ATLANTIC SIDE                         
            FL
NOAA Chart: 11449                           Latitude:   24° 45.3' N (  24.75500)
USGS Quad:  GRASSY KEY                      Longitude:  80° 57.5' W ( -80.95830)


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


                         BENCH MARK STAMPING:  NO 5 1975
                         DESIGNATION:          872 3933 TIDAL 5

MONUMENTATION:           Tidal Station disk                    VM#:         6285
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0863
SETTING CLASSIFICATION:  Concrete walkway                      OPUS PID:        
LATITUDE:   24° 45.3' N (  24.75500)          LONGITUDE:  80° 57.5' W ( -80.95830)


The bench mark is a disk set in the walk near the NE entrance to the apartment
building at the west corner of the property, 34.59 m (113.5 ft) west of bench
mark NO 4 1975, and 3.51 m (11.5 ft) NW of the north corner of the building.



                         BENCH MARK STAMPING:  3933 F 1982
                         DESIGNATION:          872 3933 F TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         6286
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0865
SETTING CLASSIFICATION:  Concrete step                         OPUS PID:        
LATITUDE:   24° 45.3' N (  24.75500)          LONGITUDE:  80° 57.5' W ( -80.95830)


The bench mark is a disk set in the steps leading from the beach to the pool,
10.39 m (34.1 ft) SW of the east corner of the pools patio, 3.69 m (12.1 ft) SE
of the south corner of the pool, and 3.26 m (10.7 ft) NE of the south corner of
the pools patio, and 1 m (2 ft) above ground.

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

                                                                                
Station ID: 8723933                         PUBLICATION DATE:  12/12/2003
Name:       GRASSY KEY, ATLANTIC SIDE                         
            FL
NOAA Chart: 11449                           Latitude:   24° 45.3' N (  24.75500)
USGS Quad:  GRASSY KEY                      Longitude:  80° 57.5' W ( -80.95830)


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


                         BENCH MARK STAMPING:  3933 G 1982
                         DESIGNATION:          872 3933 G TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         6287
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0864
SETTING CLASSIFICATION:  Concrete walkway                      OPUS PID:        
LATITUDE:   24° 45.3' N (  24.75500)          LONGITUDE:  80° 57.5' W ( -80.95830)


The bench mark is a disk set in a concrete walkway, 13 m (43 ft) NW of a
stairway, 2.44 m (8.0 ft) NE of the center of a path between the two-story
apartment building, and 1.43 m (4.7 ft) west of the west corner of the
northeasternmost two-story apartment building.

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

                                                                                
Station ID: 8723933                         PUBLICATION DATE:  12/12/2003
Name:       GRASSY KEY, ATLANTIC SIDE                         
            FL
NOAA Chart: 11449                           Latitude:   24° 45.3' N (  24.75500)
USGS Quad:  GRASSY KEY                      Longitude:  80° 57.5' W ( -80.95830)


                            T I D A L   D A T U M S 


Tidal datums at GRASSY KEY, ATLANTIC SIDE based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           June 1975 - June 1975
     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   =  0.628
     North American Vertical Datum              NAVD88 =  0.598
     MEAN HIGH WATER                            MHW    =  0.568
     MEAN SEA LEVEL                             MSL    =  0.324
     MEAN TIDE LEVEL                            MTL    =  0.311
     MEAN LOW WATER                             MLW    =  0.054
     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 4 1975                                   1.816    1.248
     NO 3 1975                                   1.803    1.235
     NO 5 1975                                   1.789    1.221
     3933 F 1982                                 1.936    1.368
     3933 G 1982                                 1.853    1.285


Foot Notes:

Bench marks 3933 F 1982 and 3933 G 1982 are based on one differential leveling
connection and do not meet the quality control standards of the NOS. Therefore,
caution should be used when deriving elevations for these marks.

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

                                                                                
Station ID: 8723933                         PUBLICATION DATE:  12/12/2003
Name:       GRASSY KEY, ATLANTIC SIDE                         
            FL
NOAA Chart: 11449                           Latitude:   24° 45.3' N (  24.75500)
USGS Quad:  GRASSY KEY                      Longitude:  80° 57.5' W ( -80.95830)


                             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 8723933 GRASSY KEY, ATLANTIC SIDE, FL

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