U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 05/31/1988
Station ID: 8669299 SUPERCEDED DATE: 04/21/2003
Name: HILTON HEAD ISLAND, THE FOLLY
SOUTH CAROLINA
NOAA Chart: 11516 Latitude: 32° 11.4' N
USGS Quad: HILTON HEAD Longitude: 80° 42.1' W
To reach the tidal bench marks from the east end of the James Byones bridge
(U.S. Highway 278) over Skull Creek, proceed SE and SW on U.S. Highway 278 for
6.8 miles (10.9 km) to County Road S-7-200 leading to Singleton Beach, turn left
onto County Road S-7-200 and go SE for 0.3 mile (0.5 km) to a small bridge over
The Folly. The bench marks are along County Road S-7-200 between U.S. Highway
278 and The Folly. The tide gage and staff were at the middle of the bridge on
the north side.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9299 A 1979
MONUMENTATION: Survey Disk VM#: 4607
AGENCY: PID#: CK2076
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 33.9 feet (10.3 m) NNE of a utility pole, 15.5 feet (4.7 m)
NNW of the NE corner of the bridge curb, 14.8 feet (4.5 m) NE of the centerline
of County Road S-7-200, and 1.7 feet (0.5 m) SW of a steel witness post. The
bench mark is at ground level, crimped to a stainless steel rod driven 48 feet
(15 m), and encased in a PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 9299 C 1979
MONUMENTATION: Survey Disk VM#: 4608
AGENCY: PID#: CK2074
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 97.7 feet (29.8 m) SSE of road sign 278 on the east side of
County Road S-7-200, 25.4 feet (7.7 m) NE of the centerline of County Road
S-7-200, 21.1 feet (6.4 m) WNW of a light dirt road heading east off County
Road S-7-200, and 2.5 feet (0.8 m) ESE of a steel witness post. The bench mark
is crimped to a stainless steel rod driven 42 feet (12.3 m) 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 4
PUBLICATION DATE: 05/31/1988
Station ID: 8669299 SUPERCEDED DATE: 04/21/2003
Name: HILTON HEAD ISLAND, THE FOLLY
SOUTH CAROLINA
NOAA Chart: 11516 Latitude: 32° 11.4' N
USGS Quad: HILTON HEAD Longitude: 80° 42.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9299 E 1979
MONUMENTATION: Survey Disk VM#: 4609
AGENCY: PID#: CK2073
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 51.2 feet (15.6 m) SE of the centerline of U.S. Highway 278,
38.2 feet (11.6 m) SW of a telephone junction box, 29.4 feet (9.0 m) NE of the
centerline of County Road S-7-200, 24.0 feet (7.3 m) NW of utility pole
#E-BR1279-MVPA 635, and 9.7 feet (3.0 m) north of a Stop sign. The bench mark
is crimped to a stainless steel rod driven 42 feet (13 m) to refusal, and set
encased in a PVC pipe.
BENCH MARK STAMPING: 9299 F 1981
MONUMENTATION: Survey Disk VM#: 4610
AGENCY: PID#: CK2077
SETTING CLASSIFICATION: Concrete Monument
The bench mark is 74.8 feet (22.8 m) SW of the SW corner of a cinder block
building, 30.0 feet (9.1 m) WSW of the centerline of County Road S-7-200, 3.3
feet (1.0 m) SSE of utility pole #A75-9, 1.4 feet (0.4 m) NE of a metal witness
post with sign, and 0.4 foot (0.12 m) above ground level.
BENCH MARK STAMPING: 9299 G 1981
MONUMENTATION: Survey Disk VM#: 4611
AGENCY: PID#: CK2075
SETTING CLASSIFICATION: Concrete Monument
The bench mark is 46.5 feet (14.2 m) SSE of a paved driveway, 24.5 feet (7.5 m)
ENE of the centerline of County Road S-7-200, approximately 7 feet (2 m) ENE of
a drainage ditch east of County Road S-7-200, 2.0 feet (0.6 m) NE of a metal
witness post with sign, and 0.1 foot (0.03 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 05/31/1988
Station ID: 8669299 SUPERCEDED DATE: 04/21/2003
Name: HILTON HEAD ISLAND, THE FOLLY
SOUTH CAROLINA
NOAA Chart: 11516 Latitude: 32° 11.4' N
USGS Quad: HILTON HEAD Longitude: 80° 42.1' W
T I D A L D A T U M S
Tidal datums at HILTON HEAD ISLAND, THE FOLLY based on:
LENGTH OF SERIES: 12 MONTHS
TIME PERIOD: AUGUST 1979 - JULY 1980
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8665530 CHARLESTON
Elevations of tidal datums referred to Mean High Water (MHW), in FEET:
HIGHEST OBSERVED WATER LEVEL (09/04/1979) = 4.05
MEAN HIGHER HIGH WATER MHHW = 0.37
MEAN HIGH WATER MHW = 0.00
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MHW
9299 A 1979 4.31
9299 C 1979 6.62
9299 E 1979 6.30
9299 F 1981 2.68
9299 G 1981 2.83
Foot Notes:
The datums were computed by the NOS Direct Method due to flat low waters.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 05/31/1988
Station ID: 8669299 SUPERCEDED DATE: 04/21/2003
Name: HILTON HEAD ISLAND, THE FOLLY
SOUTH CAROLINA
NOAA Chart: 11516 Latitude: 32° 11.4' N
USGS Quad: HILTON HEAD Longitude: 80° 42.1' 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.