U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
To reach the tidal bench marks from the Fort Island Beach boat ramp at the west
end of County Road C-44 (West Fort Island Trail), west of Crystal River, proceed
by boat north for 1.6 km (1 statute mi) to the east end of Shell Island at the
mouth of Crystal River. The bench marks are located around the island. The
tide gage and staff were located on a 1.22 m (4.0 ft) square platform in
Crystal River at the north end of Shell Island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 7359 B 1978
DESIGNATION: 872 7359 B
MONUMENTATION: Tidal Station disk VM#: 8173
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Galvanized steel rod OPUS PID:
LATITUDE: 28° 55.4' N ( 28.92330) LONGITUDE: 82° 41.5' W ( -82.69170)
The primary bench mark is a disk located at the NE end of Shell Island, 12.41 m
(40.7 ft) west of a 0.37 m (1.2 ft) diameter twin oak tree, 2.83 m (9.3 ft) SE
of another 0.37 m (1.2 ft) diameter twin oak tree, and 1.16 m (3.8 ft) east of a
witness post. The bench mark is crimped to the top of a galvanized steel rod
driven 7.3 m (24 ft) 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 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7359 C 1979
DESIGNATION: 872 7359 C
MONUMENTATION: Tidal Station disk VM#: 8174
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Galvanized steel rod OPUS PID:
LATITUDE: 28° 55.4' N ( 28.92330) LONGITUDE: 82° 41.5' W ( -82.69170)
The bench mark is a disk located at the NE end of Shell Island, 10 m (32 ft)
north of the north edge of a sink hole, 4.21 m (13.8 ft) east of a 0.61 m (2.0
ft) diameter white oak tree, 1.22 m (4.0 ft) NE of a 0.40 m (1.3 ft) diameter
cabbage palm tree, and 0.76 m (2.5 ft) NE of a witness post. The bench mark is
crimped to the top of a galvanized steel rod driven 7.3 m (24 ft) to substantial
residence, 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 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: SHELL POINT 1857 1910 1934
DESIGNATION: SHELL POINT RESET
MONUMENTATION: Triangulation Station disk VM#: 8175
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AL0960
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 28° 55.1' N ( 28.91830) LONGITUDE: 82° 42.0' W ( -82.70000)
The bench mark is a disk set in the top of a concrete monument located at the SW
end of Shell Island, 14.63 m (48.0 ft) west of twin palmettos, 13.41 m (44.0 ft)
NE of the offshore edge of the grass in water at the point, 5 m (16 ft) west of
the centerline of a cluster of several palmettos, and 2 m (8 ft) NE of the
waters edge. NOTE: The concrete monument is severely cracked but the mark
appears stable.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: SHELL POINT NO 1 1934
DESIGNATION: SHELL POINT RM 1
MONUMENTATION: Reference Mark disk VM#: 8176
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 28° 55.4' N ( 28.92330) LONGITUDE: 82° 41.5' W ( -82.69170)
The bench mark is a disk set in the top of a square concrete monument located at
the grass line, 36.94 m (121.2 ft) NNE of triangulation station SHELL POINT 1857
1910 1934, 7 m (22 ft) inshore from the water's edge, and 6 m (21 ft) east of
the offshore edge of the treeline.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: SHELL POINT NO 2 1934
DESIGNATION: SHELL POINT RM 2
MONUMENTATION: Reference Mark disk VM#: 8177
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 28° 55.1' N ( 28.91830) LONGITUDE: 82° 42.0' W ( -82.70000)
The bench mark is a disk set in the top of a square concrete monument located at
the west end of a dense growth of brush on the south side of the island, 28.74 m
(94.3 ft) ESE of triangulation station SHELL POINT 1857 1910 1934, 13 m (44 ft)
east of twin palmettos, and 6 m (21 ft) north of the water's edge.
BENCH MARK STAMPING: 7359 D 1985
DESIGNATION: 872 7359 D
MONUMENTATION: Tidal Station disk VM#: 16471
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 28° 55.4' N ( 28.92330) LONGITUDE: 82° 41.5' W ( -82.69170)
The bench mark is a disk located at the NE end of Shell Island, 30 m (100 ft)
north of bench mark 7359 C 1979, 10 m (33 ft) west of the shoreline, 5.49 m
(18.0 ft) SE of the edge of a lagoon, and 1.22 m (4.0 ft) north of a palm tree.
The bench mark is crimped to the top of a stainless steel rod driven 9.8 m (32
ft) 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 6 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7359 E 1985
DESIGNATION: 872 7359 E
MONUMENTATION: Tidal Station disk VM#: 16472
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 28° 55.4' N ( 28.92330) LONGITUDE: 82° 41.5' W ( -82.69170)
The bench mark is a disk located at the NE end of Shell Island, 24.54 m (80.5
ft) south of bench mark 7359 C 1979, 9 m (30 ft) west of the shoreline, 1.07 m
(3.5 ft) SE of a palm tree, and 0.76 m (2.5 ft) NW of another palm tree. The
bench mark is crimped to the top of a stainless steel rod driven 2.4 m (8 ft) 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 7 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: EDE 4 1935
DESIGNATION: EDE 4
MONUMENTATION: Survey disk VM#: 16473
AGENCY: US Harbor Survey (USHS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 28° 55.4' N ( 28.92330) LONGITUDE: 82° 41.5' W ( -82.69170)
The bench mark is a disk set in the top of a concrete monument located on the
high ground at the NE end of Shell Island, 24.14 m (79.2 ft) east of bench mark
7359 B 1979, 5.33 m (17.5 ft) east of a twin-trunked oak tree, 10.58 m (34.7 ft)
ENE of a blazed 1 m (3 ft) diameter oak tree, 7.32 m (24.0 ft) NE of the
centerline of a foot path along the high ground, and 0.09 m (0.3 ft) above
ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
T I D A L D A T U M S
Tidal datums at SHELL ISLAND, CRYSTAL RIVER based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: September 1978 - November 1978
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8727520 CEDAR KEY, GULF OF MEXICO
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.924
MEAN HIGH WATER MHW = 0.832
MEAN TIDE LEVEL MTL = 0.472
MEAN SEA LEVEL MSL = 0.461
MEAN LOW WATER MLW = 0.113
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
7359 B 1978 3.901 3.069
7359 C 1979 1.278 0.446
SHELL POINT 1857 1910 1934 0.967 0.135
SHELL POINT NO 1 1934 1.294 0.462
SHELL POINT NO 2 1934 1.155 0.323
7359 D 1985 1.031 0.199
7359 E 1985 0.814 -0.018
EDE 4 1935 3.803 2.971
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 9 of 9
Station ID: 8727359 PUBLICATION DATE: 05/20/2004
Name: SHELL ISLAND, CRYSTAL RIVER
FL
NOAA Chart: 11408 Latitude: 28° 55.4' N ( 28.92330)
USGS Quad: RED LEVEL Longitude: 82° 41.5' W ( -82.69170)
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.