U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 6
Station ID: 8726347 PUBLICATION DATE: 04/21/2003
Name: EGMONT KEY, TAMPA BAY
FL
NOAA Chart: 11414 Latitude: 27° 36.1' N ( 27.60170)
USGS Quad: EGMONT KEY Longitude: 82° 45.6' W ( -82.76000)
To reach the tidal bench marks from the southern tip of Mullet Key, proceed by
boat SW for about 2.4 km (1.5 mi) to Egmont Key at the mouth of Tampa Bay. The
bench marks are in the area between the U.S. Coast Guard pier and a lighthouse.
The tide gauge and staff were on the NE end of the island on the U.S. Coast
Guard Pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6347 A 1976
DESIGNATION: 872 6347 A
MONUMENTATION: Tidal Station disk VM#: 11510
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 27° 36.1' N ( 27.60170) LONGITUDE: 82° 45.6' W ( -82.76000)
The primary bench mark is a disk located near the steps leading into the
lighthouse, 0.85 m (2.8 ft) south of the south edge of the steps going to the
lighthouse, and 1 m (2 ft) east of the east side of the lighthouse. The bench
mark is crimped to a copper-clad steel rod driven an unspecified depth to
refusal, and encased in a 4-inch PVC pipe with concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8726347 PUBLICATION DATE: 04/21/2003
Name: EGMONT KEY, TAMPA BAY
FL
NOAA Chart: 11414 Latitude: 27° 36.1' N ( 27.60170)
USGS Quad: EGMONT KEY Longitude: 82° 45.6' W ( -82.76000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6347 C 1976
DESIGNATION: 872 6347 C
MONUMENTATION: Tidal Station disk VM#: 11511
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete pad OPUS PID:
LATITUDE: 27° 36.1' N ( 27.60170) LONGITUDE: 82° 45.6' W ( -82.76000)
The bench mark is a disk set in a concrete pad on the south side of a small
warehouse, 19 m (61 ft) NE of the lighthouse, 18 m (59 ft) NE of Bench Mark 6347
A 1976, 6.68 m (21.9 ft) NE of the SE corner of a large warehouse, 1.13 m (3.7
ft) south of the south side of the small warehouse, and 0.21 m (0.7 ft) north of
the south side of the concrete pad.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8726347 PUBLICATION DATE: 04/21/2003
Name: EGMONT KEY, TAMPA BAY
FL
NOAA Chart: 11414 Latitude: 27° 36.1' N ( 27.60170)
USGS Quad: EGMONT KEY Longitude: 82° 45.6' W ( -82.76000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO V
DESIGNATION: 872 6347 TIDAL 5
ALIAS: TIDAL 5 STA III 35; V
MONUMENTATION: Tidal Station disk VM#: 11512
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AG5452
SETTING CLASSIFICATION: Concrete foundation of flagpole OPUS PID:
LATITUDE: 27° 36.0' N ( 27.60000) LONGITUDE: 82° 45.6' W ( -82.76000)
The bench mark is a disk set in the concrete base of the flagpole in front of
the old lightkeepers house, and on the east side of the pole.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8726347 PUBLICATION DATE: 04/21/2003
Name: EGMONT KEY, TAMPA BAY
FL
NOAA Chart: 11414 Latitude: 27° 36.1' N ( 27.60170)
USGS Quad: EGMONT KEY Longitude: 82° 45.6' W ( -82.76000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO VI
DESIGNATION: 872 6347 TIDAL 6
ALIAS: TIDAL 6 STA III 35; VI
MONUMENTATION: Tidal Station disk VM#: 11513
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AG5451
SETTING CLASSIFICATION: Concrete foundation of tower OPUS PID:
LATITUDE: 27° 36.1' N ( 27.60170) LONGITUDE: 82° 45.6' W ( -82.76000)
The bench mark is a disk set in the SW corner of the remains of the base of the
old radio tower at the head of the dock, on the east side of the shed on the
dock, 3 m (10 ft) west of the walk leading to the lightkeeper's house, and 2 m
(5 ft) south of the dock.
BENCH MARK STAMPING: 6347 J 1983
DESIGNATION: 872 6347 J
MONUMENTATION: Tidal Station disk VM#: 11514
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation of water cistern OPUS PID:
LATITUDE: 27° 36.1' N ( 27.60170) LONGITUDE: 82° 45.6' W ( -82.76000)
The bench mark is a disk set in the SW corner of a 3.81 x 5 x 0.76 m (12.5 x 15
x 2.5 ft) concrete base for a water cistern on the grounds of the Coast Guard
Station, 45.57 m (149.5 ft) SSE of Bench Mark 6347 C 1976, 43 m (142 ft) SE of
the center of the door to the lighthouse, 29.02 m (95.2 ft) SW of a flag pole,
14.17 m (46.5 ft) NW of the NW corner of the Coast Guard Office, and 0.76 m (2.5
ft) above ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8726347 PUBLICATION DATE: 04/21/2003
Name: EGMONT KEY, TAMPA BAY
FL
NOAA Chart: 11414 Latitude: 27° 36.1' N ( 27.60170)
USGS Quad: EGMONT KEY Longitude: 82° 45.6' W ( -82.76000)
T I D A L D A T U M S
Tidal datums at EGMONT KEY, TAMPA BAY based on:
LENGTH OF SERIES: 6 Months
TIME PERIOD: June 1990 - November 1990
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8726724 CLEARWATER BEACH, GULF OF MEXICO
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.657
MEAN HIGH WATER MHW = 0.580
North American Vertical Datum NAVD88 = 0.486
MEAN SEA LEVEL MSL = 0.355
MEAN TIDE LEVEL MTL = 0.348
MEAN LOW WATER MLW = 0.116
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6347 A 1976 1.315 0.735
6347 C 1976 1.787 1.207
NO V 1.784 1.204
NO VI 1.780 1.200
6347 J 1983 2.541 1.961
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8726347 PUBLICATION DATE: 04/21/2003
Name: EGMONT KEY, TAMPA BAY
FL
NOAA Chart: 11414 Latitude: 27° 36.1' N ( 27.60170)
USGS Quad: EGMONT KEY Longitude: 82° 45.6' W ( -82.76000)
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.