U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 08/06/1984
Station ID: 8663261 SUPERCEDED DATE: 04/21/2003
Name: CEDAR ISLAND, NORTH SANTEE BAY
SOUTH CAROLINA
NOAA Chart: 11531 Latitude: 33° 8.4' N
USGS Quad: Santee Point Longitude: 79° 14.7' W
To reach the tidal bench marks from intersection of highway 17 and Route 521 in
Georgetown, proceed South on Highway 17 for 1.9 miles (3.1 km), left on Route 18
for 7.5 miles (12.1 km) to dead end at Ferry Terminal/Public Landing across from
South Island, by boat, continue south on intracoastal waterway for 4.2 miles
(6.8 km), then south into north Santee Bay for 4.4 miles (7.1 km), to the
Eastern Shore of Cedar Island. The bench marks are located in the immediate
vicinity of the dock and observation tower and the tide gage and staff were
located of the state-owned dock at Cedar Island campgrounds.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 3261 A 1982
MONUMENTATION: Survey Disk VM#: 3973
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 36.0 feet (11.0 m), south of south face of 2.5 feet (0.8 m),
diameter pine tree, 33.8 feet (10.3 m) WSW of centerline of dock at edge of
land, and 2.1 feet (0.6 m), NE of south post of Cedar Island sign. The bench
mark is level with the ground, and crimped to a stainless steel rod driven 36
feet (11 m) to refusal and encased in a 5 -inch PVC pipe and concrete
kickblock.
BENCH MARK STAMPING: 3261 B 1982
MONUMENTATION: Survey Disk VM#: 3974
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 164.0 feet (50.0 m), south of bench mark 3261 A 1982, 43.0
feet (13.1), west of the west face of a 6.0 feet (1.8 m), diameter oak tree, 7.3
feet (2.2 m), NW of north face of 2.5 feet (0.8 m) diameter pine tree, and 0.7
foot (0.2 m) north of witness post with sign. The bench mark is level with the
ground, crimped to stainless steel rod driven 32 feet (10 m) to refusal and
encased in a 5-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 08/06/1984
Station ID: 8663261 SUPERCEDED DATE: 04/21/2003
Name: CEDAR ISLAND, NORTH SANTEE BAY
SOUTH CAROLINA
NOAA Chart: 11531 Latitude: 33° 8.4' N
USGS Quad: Santee Point Longitude: 79° 14.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3261 C 1982
MONUMENTATION: Survey Disk VM#: 3975
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 112.0 feet (34.1 m), NNW of bench mark 3261 A 1982, 38.6 feet
(11.8 M), SW of SW corner of wood latrine, 15.5 feet (4.7 m), north of NE leg of
observation tower, and 2.0 feet (0.6 m), East of witness post with sign. The
bench mark is at ground level, crimped to stainless steel rod driven 36 feet (11
m) to refusal and encased in a 5-inch PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 3261 D 1982
MONUMENTATION: Survey Disk VM#: 3976
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 101.0 feet (30.8 M), NW of Bench Mark 3261 C 1982, 60.0 feet
(18.3 m), north of NE corner of wooden latrine, 30.0 feet (9.1 m), west of
approximate shoreline and 1.9 feet (0.6 m) east of steel witness post with sign.
The bench mark is level with the ground, crimped to a stainless steel rod
driven 36 feet (11 m) to refusal and encased in a 5-inch PVC pipe and concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 08/06/1984
Station ID: 8663261 SUPERCEDED DATE: 04/21/2003
Name: CEDAR ISLAND, NORTH SANTEE BAY
SOUTH CAROLINA
NOAA Chart: 11531 Latitude: 33° 8.4' N
USGS Quad: Santee Point Longitude: 79° 14.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3261 E 1982
MONUMENTATION: Survey Disk VM#: 3977
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 218.0 feet (66.4 m) NNW of bench mark 3261 D 1982, 67.0 feet
(20.4 m), NW of 2.0 feet (0.6 m) diameter pine tree, 19.0 feet (5.8 m), west of
approximate shoreline, and 2.3 feet (0.7 m) east of witness post with sign. the
bench mark is at ground level, crimped to a stainless steel rod driven 36 feet
(11 m) to refusal and encased in a 5-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 08/06/1984
Station ID: 8663261 SUPERCEDED DATE: 04/21/2003
Name: CEDAR ISLAND, NORTH SANTEE BAY
SOUTH CAROLINA
NOAA Chart: 11531 Latitude: 33° 8.4' N
USGS Quad: Santee Point Longitude: 79° 14.7' W
T I D A L D A T U M S
Tidal datums at CEDAR ISLAND, NORTH SANTEE BAY based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: APRIL-SEPTEMBER l982
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8665530 CHARLESTON
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (06/18/1982) = 7.02
MEAN HIGHER HIGH WATER MHHW = 4.69
MEAN HIGH WATER MHW = 4.37
MEAN TIDE LEVEL MTL = 2.28
MEAN LOW WATER MLW = 0.18
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (04/06/1982) = -1.01
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
3261 A 1982 6.34 1.97
3261 B 1982 5.73 1.36
3261 C 1982 8.07 3.70
3261 D 1982 7.19 2.82
3261 E 1982 8.74 4.37
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 08/06/1984
Station ID: 8663261 SUPERCEDED DATE: 04/21/2003
Name: CEDAR ISLAND, NORTH SANTEE BAY
SOUTH CAROLINA
NOAA Chart: 11531 Latitude: 33° 8.4' N
USGS Quad: Santee Point Longitude: 79° 14.7' W
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 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.