U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 01/06/1988
Station ID: 8664992 SUPERCEDED DATE: 04/21/2003
Name: NORTH DEWEES ISLAND, CAPERS INLET
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 51.0' N
USGS Quad: CAPERS INLET Longitude: 79° 42.2' W
To reach the tidal bench marks proceed by boat to the NE end of Dewees Island in
Capers Inlet. The bench marks are located along a dirt road leading south from
the shoreline of Capers Inlet. The tide gage and staff were located near the NE
corner of the pier at the north end of the dirt road.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: N.D.I. NO 1 1975
MONUMENTATION: Survey Disk VM#: 4124
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is located in a small group of cedar trees at the north end of
Dewees Island, 61.5 feet (18.7 m) SSE of the SE corner of a wooden pier, 20 feet
(6 m) east of the centerline of the dirt road, 2.3 feet (0.7 m) NE of a metal
witness post with sign, and 2.1 feet (0.6 m) ESE of a second witness post with
sign. The bench mark is 0.1 foot (0.03 m) below ground level, crimped to a
copper-clad steel rod driven to an unspecified depth, and encased in a PVC pipe
and concrete kickblock.
BENCH MARK STAMPING: N.D.I. NO 2 1975
MONUMENTATION: Survey Disk VM#: 4125
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 150.1 feet (45.8 m) south of Bench Mark N.D.I. NO 1 1975, 12.4
feet (3.8 m) east of the centerline of the dirt road, and 1.4 feet (0.4 m)
SE of a witness post with sign. The bench mark is crimped to a copper-clad
steel rod driven to an unspecified depth, 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
PUBLICATION DATE: 01/06/1988
Station ID: 8664992 SUPERCEDED DATE: 04/21/2003
Name: NORTH DEWEES ISLAND, CAPERS INLET
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 51.0' N
USGS Quad: CAPERS INLET Longitude: 79° 42.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: N.D.I. NO 3 1975
MONUMENTATION: Survey Disk VM#: 4126
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 125.0 feet (38.1 m) south of Bench Mark N.D.I. NO 2 1975, 12.3
feet (3.7 m) east of the centerline of the dirt road, 3.2 feet (1.0 m) north of
a steel witness post with sign, and 2.5 feet (0.8 m) ESE of a second witness
post with sign. The bench mark is at ground level, crimped to a copper-clad
steel rod driven to an unspecified depth, and encased in a PVC pipe and concrete
kickblock.
BENCH MARK STAMPING: N.D.I. NO 4 1975
MONUMENTATION: Survey Disk VM#: 4127
AGENCY: PID:
SETTING CLASSIFICATION: Copper Pipe
The bench mark is 76 feet (23 m) SSE of Bench Mark N.D.I. NO 3 1975, 17.2 feet
(5.2 m) east of the centerline of the dirt road, and 2.6 feet (0.8 m) east of a
witness post with sign. The bench mark is 0.5 foot (0.2 m) above ground level,
brazed to the top of a copper pipe surrounded by a 1.2-foot (0.4 m) diameter
concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 01/06/1988
Station ID: 8664992 SUPERCEDED DATE: 04/21/2003
Name: NORTH DEWEES ISLAND, CAPERS INLET
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 51.0' N
USGS Quad: CAPERS INLET Longitude: 79° 42.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: N.D.I. NO 5 1975
MONUMENTATION: Survey Disk VM#: 4128
AGENCY: PID:
SETTING CLASSIFICATION: Copper Pipe
The bench mark is 151.4 feet (46.1 m) south of Bench Mark N.D.I. NO 4 1975, 11.8
feet (3.6 m) east of the centerline of the dirt road, 1.8 feet (0.5 m) north of
a steel witness post with sign, and 1.3 feet (0.4 m) west of a second witness
post with sign. The bench mark is 0.5 foot (0.2 m) above ground level, brazed
to the top of a copper pipe surrounded by a 1.1-foot (0.3 m) diameter concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 01/06/1988
Station ID: 8664992 SUPERCEDED DATE: 04/21/2003
Name: NORTH DEWEES ISLAND, CAPERS INLET
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 51.0' N
USGS Quad: CAPERS INLET Longitude: 79° 42.2' W
T I D A L D A T U M S
Tidal datums at NORTH DEWEES ISLAND, CAPERS INLET based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: OCTOBER-DECEMBER 1975
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8664941 CAPERS CREEK
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (10/05/1975) = 6.81
MEAN HIGHER HIGH WATER MHHW = 5.35
MEAN HIGH WATER MHW = 5.01
MEAN TIDE LEVEL MTL = 2.61
MEAN LOW WATER MLW = 0.20
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/28/1975) = -0.73
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
N.D.I. NO 1 1975 8.93 3.92
N.D.I. NO 2 1975 7.89 2.88
N.D.I. NO 3 1975 8.10 3.09
N.D.I. NO 4 1975 10.19 5.18
N.D.I. NO 5 1975 8.71 3.70
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 01/06/1988
Station ID: 8664992 SUPERCEDED DATE: 04/21/2003
Name: NORTH DEWEES ISLAND, CAPERS INLET
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 51.0' N
USGS Quad: CAPERS INLET Longitude: 79° 42.2' 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.