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.