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Bench Mark Sheet for 8724257, HOWE KEY NE POINT 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Superseded Epoch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Small blue map location marker Unpublished bench mark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  6

                                                                                
Station ID: 8724257                         PUBLICATION DATE:  03/09/2004
Name:       HOWE KEY NE POINT                                 
            FL
NOAA Chart: 11448                           Latitude:   24° 45.5' N (  24.75830)
USGS Quad:  CONTENT KEYS                    Longitude:  81° 25.7' W ( -81.42830)


To reach the tidal bench marks from Bogie Channel Bridge on Big Pine Key,
proceed NW by boat 11 km (7 statue mi) to a narrow peninsula which forms the
northern tip of Howe Key.  The bench marks are located along the northern tip of
the Key.  The tide gage and staff were located offshore north of the northern
tip of Howe Key.


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


                 PRIMARY BENCH MARK STAMPING:  NO 4 1974
                         DESIGNATION:          872 4257 TIDAL 4

MONUMENTATION:           Tidal Station disk                    VM#:         6868
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   24° 45.5' N (  24.75830)          LONGITUDE:  81° 25.7' W ( -81.42830)


The primary bench mark is a disk, 122 m (400 ft) SE of the most northern point
of the eastern shore, 61 m (200 ft) from the outer edge of the east side of the
Key, 46 m (150 ft) WSW of a witness sign nailed to a tree, 44.81 m (147.0 ft)
ENE of bench mark NO 5 1974, and 2.44 m (8.0 ft) SW of a witness sign nailed to
a tree.  The bench mark is set 9 cm (0.3 ft) above ground level, crimped to the
top of a copper-clad rod driven an unspecified depth to refusal.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8724257                         PUBLICATION DATE:  03/09/2004
Name:       HOWE KEY NE POINT                                 
            FL
NOAA Chart: 11448                           Latitude:   24° 45.5' N (  24.75830)
USGS Quad:  CONTENT KEYS                    Longitude:  81° 25.7' W ( -81.42830)


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


                         BENCH MARK STAMPING:  HOW 1935
                         DESIGNATION:          HOW 1935

MONUMENTATION:           Triangulation Station disk            VM#:         6865
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AA1577
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   24° 45.4' N (  24.75670)          LONGITUDE:  81° 25.7' W ( -81.42830)


The bench mark is a disk set flush in a concrete monument, 200 m (656 ft) NE of
the SW point of the peninsula, 65 m (213 ft) north of the scattered mangroves at
the shore bight, 55 m (180 ft) SE of the inshore edge of mangroves, and 0.21 m
(0.7 ft) above ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8724257                         PUBLICATION DATE:  03/09/2004
Name:       HOWE KEY NE POINT                                 
            FL
NOAA Chart: 11448                           Latitude:   24° 45.5' N (  24.75830)
USGS Quad:  CONTENT KEYS                    Longitude:  81° 25.7' W ( -81.42830)


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


                         BENCH MARK STAMPING:  HOW 1935 RM 1
                         DESIGNATION:          HOW 1935 RM 1

MONUMENTATION:           Reference Mark disk                   VM#:         6866
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   24° 45.5' N (  24.75830)          LONGITUDE:  81° 25.7' W ( -81.42830)


The bench mark is a disk set flush in a concrete monument, 70 m (230 ft) SE of
the inshore edge of mangroves, 26.03 m (85.4 ft) ENE of bench mark HOW 1935, and
0.21 m (0.7 ft) above ground level.



                         BENCH MARK STAMPING:  HOW 1935 RM 2
                         DESIGNATION:          872 4257 HOW 1935 RM 2

MONUMENTATION:           Reference Mark disk                   VM#:         6867
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   24° 45.5' N (  24.75830)          LONGITUDE:  81° 25.7' W ( -81.42830)


The bench mark is a disk set flush in a concrete monument, 40 m (130 ft) NE of
the mangroves at the shore bight, 32.70 m (107.3 ft) NNE of bench mark HOW 1935
RM 1, 25.44 m (83.5 ft) SSE of bench mark HOW 1935, and 0.40 m (1.3 ft) above
ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8724257                         PUBLICATION DATE:  03/09/2004
Name:       HOWE KEY NE POINT                                 
            FL
NOAA Chart: 11448                           Latitude:   24° 45.5' N (  24.75830)
USGS Quad:  CONTENT KEYS                    Longitude:  81° 25.7' W ( -81.42830)


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


                         BENCH MARK STAMPING:  NO 5 1974
                         DESIGNATION:          872 4257 TIDAL 5

MONUMENTATION:           Tidal Station disk                    VM#:         6869
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   24° 45.5' N (  24.75830)          LONGITUDE:  81° 25.7' W ( -81.42830)


The bench mark is a disk, 107 m (350 ft) from the outer edge of the east side of
the Key, 53 m (173 ft) east of bench mark HOW 1935, 45.57 m (149.5 ft) ENE of
bench mark HOW 1935 RM 2, and 28.80 m (94.5 ft) ESE of bench mark HOW 1935 RM 1.
 The bench mark is set 15 cm (0.5 ft) above ground level, crimped to the top of
a copper-clad rod driven an unspecified depth to refusal.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8724257                         PUBLICATION DATE:  03/09/2004
Name:       HOWE KEY NE POINT                                 
            FL
NOAA Chart: 11448                           Latitude:   24° 45.5' N (  24.75830)
USGS Quad:  CONTENT KEYS                    Longitude:  81° 25.7' W ( -81.42830)


                            T I D A L   D A T U M S 


Tidal datums at HOWE KEY NE POINT based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           October 1974 - October 1974
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8724580 KEY WEST


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.832
     MEAN HIGH WATER                            MHW    =  0.778
     MEAN SEA LEVEL                             MSL    =  0.441
     MEAN TIDE LEVEL                            MTL    =  0.437
     MEAN LOW WATER                             MLW    =  0.096
     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 1974                                   1.069    0.291
     HOW 1935                                    0.830    0.052
     HOW 1935 RM 1                               0.912    0.134
     HOW 1935 RM 2                               1.186    0.408
     NO 5 1974                                   1.006    0.228


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8724257                         PUBLICATION DATE:  03/09/2004
Name:       HOWE KEY NE POINT                                 
            FL
NOAA Chart: 11448                           Latitude:   24° 45.5' N (  24.75830)
USGS Quad:  CONTENT KEYS                    Longitude:  81° 25.7' W ( -81.42830)


                             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 8724257 HOWE KEY NE POINT, FL

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