Bench Mark Sheet for 8726942, NORTH ANCLOTE 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 8726942                         PUBLICATION DATE:  01/06/2004
Name:       NORTH ANCLOTE KEY                                 
            FL
NOAA Chart: 11410                           Latitude:   28° 12.6' N (  28.21000)
USGS Quad:  TARPON SPRINGS                  Longitude:  82° 50.4' W ( -82.84000)


To reach the tidal bench marks from Tarpon Springs, proceed NW by boat to the
most southeastern of the most northerly of the Anclote Keys in the Gulf of
Mexico.  The gage and staff were located 46 m (150 ft) offshore and the bench
marks are on the northern part of the island above the shoreline.


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


                 PRIMARY BENCH MARK STAMPING:  6942 A 1976
                         DESIGNATION:          872 6942 A

MONUMENTATION:           Tidal Station disk                    VM#:         7671
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   28° 12.6' N (  28.21000)          LONGITUDE:  82° 50.4' W ( -82.84000)


The primary bench mark is a disk located 12 m (38 ft) SSW of the shoreline, 3 m
(9 ft) south of a pine tree with a witness sign attached, and 0.30 m (1.0 ft) NW
of a palm tree.  The bench mark is at ground level, crimped to the top of a
copper-clad steel rod driven an unspecified depth to refusal, and encased in a
PVC pipe and concrete kickblock.

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

                                                                                
Station ID: 8726942                         PUBLICATION DATE:  01/06/2004
Name:       NORTH ANCLOTE KEY                                 
            FL
NOAA Chart: 11410                           Latitude:   28° 12.6' N (  28.21000)
USGS Quad:  TARPON SPRINGS                  Longitude:  82° 50.4' W ( -82.84000)


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


                         BENCH MARK STAMPING:  6942 C 1976
                         DESIGNATION:          872 6942 C

MONUMENTATION:           Tidal Station disk                    VM#:         7673
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   28° 12.6' N (  28.21000)          LONGITUDE:  82° 50.4' W ( -82.84000)


The bench mark is a disk located 22.10 m (72.5 ft) south of bench mark 6942 B
1976, 2 m (7 ft) NW of a mangrove line, 1.71 m (5.6 ft) SSE of a twin pine tree,
and 1.68 m (5.5 ft) east of a pine tree with a witness sign attached.  The bench
mark is at ground level, crimped to the top of a copper-clad steel rod driven an
unspecified depth to refusal, and encased in a PVC pipe and concrete kickblock.



                         BENCH MARK STAMPING:  6942 D 1976
                         DESIGNATION:          872 6942 D

MONUMENTATION:           Tidal Station disk                    VM#:         7674
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   28° 12.6' N (  28.21000)          LONGITUDE:  82° 50.4' W ( -82.84000)


The bench mark is a disk located 18 m (59 ft) SW of bench mark 6942 C 1976,
11.49 m (37.7 ft) SE of a pine tree, and 11 m (37 ft) NW of a mangrove line. 
The bench mark is 0.09 m (0.3 ft) above ground level, crimped to the top of a
copper-clad steel rod driven an unspecified depth to refusal, and encased in a
PVC pipe and concrete kickblock.

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

                                                                                
Station ID: 8726942                         PUBLICATION DATE:  01/06/2004
Name:       NORTH ANCLOTE KEY                                 
            FL
NOAA Chart: 11410                           Latitude:   28° 12.6' N (  28.21000)
USGS Quad:  TARPON SPRINGS                  Longitude:  82° 50.4' W ( -82.84000)


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


                         BENCH MARK STAMPING:  6942 F 1983
                         DESIGNATION:          872 6942 F

MONUMENTATION:           Tidal Station disk                    VM#:         7675
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   28° 12.6' N (  28.21000)          LONGITUDE:  82° 50.4' W ( -82.84000)


The bench mark is a disk set in the top of a concrete monument on the NE end of
the southernmost key of the three north keys, 12.74  m (41.8 ft) SE of bench
mark 6942 A 1976, 8.69 m (28.5 ft) north of a cabbage palm, 5 m (16 ft) west of
the shoreline, 0.18 m (0.6 ft) east of a witness post, and 0.21 m (0.7 ft) above
ground level.



                         BENCH MARK STAMPING:  6942 G 1983
                         DESIGNATION:          872 6942 G

MONUMENTATION:           Tidal Station disk                    VM#:         7676
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete monument                     OPUS PID:        
LATITUDE:   28° 12.6' N (  28.21000)          LONGITUDE:  82° 50.4' W ( -82.84000)


The bench mark is a disk set in the top of a concrete monument on the NE end of
the southernmost key of the three north keys, 23 m (75 ft) north of bench mark
6942 C 1976, 22.49 m (73.8 ft) west of bench mark 6942 A 1976, and 2.07 m (6.8
ft) south of a cabbage palm, 1 foot (0.3 m) north of a witness post, and 0.12 m
(0.4 ft) above ground level.

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

                                                                                
Station ID: 8726942                         PUBLICATION DATE:  01/06/2004
Name:       NORTH ANCLOTE KEY                                 
            FL
NOAA Chart: 11410                           Latitude:   28° 12.6' N (  28.21000)
USGS Quad:  TARPON SPRINGS                  Longitude:  82° 50.4' W ( -82.84000)


                            T I D A L   D A T U M S 


Tidal datums at NORTH ANCLOTE KEY based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           March 1976 - March 1976
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8726924 ANCLOTE RIVER


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.936
     MEAN HIGH WATER                            MHW    =  0.827
     MEAN SEA LEVEL                             MSL    =  0.505
     MEAN TIDE LEVEL                            MTL    =  0.494
     MEAN LOW WATER                             MLW    =  0.161
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     6942 A 1976                                 1.472    0.645
     6942 C 1976                                 1.082    0.255
     6942 D 1976                                 1.765    0.938
     6942 F 1983                                 1.649    0.822
     6942 G 1983                                 1.877    1.050


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

                                                                                
Station ID: 8726942                         PUBLICATION DATE:  01/06/2004
Name:       NORTH ANCLOTE KEY                                 
            FL
NOAA Chart: 11410                           Latitude:   28° 12.6' N (  28.21000)
USGS Quad:  TARPON SPRINGS                  Longitude:  82° 50.4' W ( -82.84000)


                             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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