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Bench Mark Sheet for 8723691, PT. CHARLES, GAGE C, KEY LARGO 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 8723691                         PUBLICATION DATE:  05/23/2003
Name:       PT. CHARLES, GAGE 'C', KEY LARGO                  
            FL
NOAA Chart: 11462                           Latitude:   25°  4.9' N (  25.08170)
USGS Quad:  ROCK HARBOR                     Longitude:  80° 27.0' W ( -80.45000)


To reach the tidal bench marks from the post office in Key Largo, proceed south
on U.S. Highway 1 for 1.1 km (0.7 mi) to the Key Largo Moose Lodge at the
intersection of Griffins Way, then proceed SE on Griffins Way for 0.3 km (0.2
mi) to the end of the road. The bench marks are on a sea wall at a private
residence and at the Moose Lodge.  The tide gage and staff were attached to the
sea wall west of bench mark NO 1 1975.


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


                 PRIMARY BENCH MARK STAMPING:  NO 2 1975
                         DESIGNATION:          872 3691 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:         5973
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AC3361
SETTING CLASSIFICATION:  Concrete sea wall                     OPUS PID:        
LATITUDE:   25°  4.9' N (  25.08170)          LONGITUDE:  80° 27.0' W ( -80.45000)


The primary bench mark is a disk set flush in the north end of the concrete sea
wall, 23 m (77 ft) north of bench mark NO 1 1975, 1.13 m (3.7 ft) west of the
east edge of the sea wall, and 0.24 m (0.8 ft) south of the north end of the sea
wall.



                         BENCH MARK STAMPING:  NO 1 1975
                         DESIGNATION:          872 3691 TIDAL 1

MONUMENTATION:           Tidal Station disk                    VM#:         5972
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AC3362
SETTING CLASSIFICATION:  Concrete sea wall                     OPUS PID:        
LATITUDE:   25°  4.9' N (  25.08170)          LONGITUDE:  80° 27.0' W ( -80.45000)


The bench mark is a disk set flush in the corner of the concrete sea wall near
the SE corner of a private residence, 24 m (79 ft) south of the north end of the
sea wall, and 11.43 m (37.5 ft) west of the east end of the sea wall.

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

                                                                                
Station ID: 8723691                         PUBLICATION DATE:  05/23/2003
Name:       PT. CHARLES, GAGE 'C', KEY LARGO                  
            FL
NOAA Chart: 11462                           Latitude:   25°  4.9' N (  25.08170)
USGS Quad:  ROCK HARBOR                     Longitude:  80° 27.0' W ( -80.45000)


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


                         BENCH MARK STAMPING:  NO 4 1975
                         DESIGNATION:          872 3691TIDAL 4

MONUMENTATION:           Tidal Station disk                    VM#:        15844
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AC3360
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   25°  4.9' N (  25.08170)          LONGITUDE:  80° 27.0' W ( -80.45000)


The bench mark is a disk set in the top of a rock outcropping located NW of the
workshop utility building, 35 m (115 ft) SW of the NW corner of the two-story
house, 14.63 m (48.0 ft) south of the centerline of the drive, 12.89 m (42.3 ft)
north of a fenceline, and 8.38 m (27.5 ft) NW of a workshop utility building.



                         BENCH MARK STAMPING:  NO 5 1975
                         DESIGNATION:          872 3691TIDAL 5

MONUMENTATION:           Tidal Station disk                    VM#:        15845
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AC3354
SETTING CLASSIFICATION:  Concrete storm drain                  OPUS PID:        
LATITUDE:   25°  4.9' N (  25.08170)          LONGITUDE:  80° 27.0' W ( -80.45000)


The bench mark is a disk set flush in top of a storm drain on the NW side of the
northbound lane of U.S. Highway 1, 9.27 m (30.4 ft) NE of a telephone pole, 7 m
(22 ft) east of the NE corner of the east wing of the Moose Lodge, 5.18 m (17.0
ft) NE of a sign, and 0.3 m (1 ft) below the level of the highway.

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

                                                                                
Station ID: 8723691                         PUBLICATION DATE:  05/23/2003
Name:       PT. CHARLES, GAGE 'C', KEY LARGO                  
            FL
NOAA Chart: 11462                           Latitude:   25°  4.9' N (  25.08170)
USGS Quad:  ROCK HARBOR                     Longitude:  80° 27.0' W ( -80.45000)


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


                         BENCH MARK STAMPING:  NO 3 1975
                         DESIGNATION:          872 3691 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:        17065
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete slab                         OPUS PID:        
LATITUDE:   25°  4.9' N (  25.08170)          LONGITUDE:  80° 27.0' W ( -80.45000)


The bench mark is a disk set flush in a concrete slab on the side of Mr. L.B.
Griffin residence, 35 m (114 ft) NW of bench mark NO 1,  25.45 m (83.5 ft) SW of
bench mark NO 2, and 6.22 m (20.4 ft) south of NE corner of residence.  

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

                                                                                
Station ID: 8723691                         PUBLICATION DATE:  05/23/2003
Name:       PT. CHARLES, GAGE 'C', KEY LARGO                  
            FL
NOAA Chart: 11462                           Latitude:   25°  4.9' N (  25.08170)
USGS Quad:  ROCK HARBOR                     Longitude:  80° 27.0' W ( -80.45000)


                            T I D A L   D A T U M S 


Tidal datums at PT. CHARLES, GAGE 'C', KEY LARGO based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           May 1975 - July 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   =  0.604
     MEAN HIGH WATER                            MHW    =  0.576
     North American Vertical Datum              NAVD88 =  0.524
     MEAN TIDE LEVEL                            MTL    =  0.301
     MEAN SEA LEVEL                             MSL    =  0.275
     MEAN LOW WATER                             MLW    =  0.026
     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 2 1975                                   1.053    0.477
     NO 1 1975                                   1.052    0.476
     NO 4 1975                                   1.077    0.501
     NO 5 1975                                   3.339    2.763
     NO 3 1975                                   1.187    0.611


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

                                                                                
Station ID: 8723691                         PUBLICATION DATE:  05/23/2003
Name:       PT. CHARLES, GAGE 'C', KEY LARGO                  
            FL
NOAA Chart: 11462                           Latitude:   25°  4.9' N (  25.08170)
USGS Quad:  ROCK HARBOR                     Longitude:  80° 27.0' W ( -80.45000)


                             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 8723691 PT. CHARLES, GAGE C, KEY LARGO, FL

Revised: 08/08/2018
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services