U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8660147 PUBLICATION DATE: 05/20/2004
Name: DUNN SOUND, NORTH, LITTLE RIVER
SC
NOAA Chart: 11535 Latitude: 33° 51.6' N ( 33.86000)
USGS Quad: LITTLE RIVER Longitude: 78° 34.8' W ( -78.58000)
To reach the tidal bench marks from the overpass of State Road 90 over U.S.
Highway 17 at Little River, proceed west on State Road 90 for 0.2 km (0.1 mi),
turn left onto a paved road following the signs for Cherry Grove for 0.2 km (0.1
mi), turn left onto State Road S-26-20 for about 183 m (600 ft) to the first
intersection, turn left onto Little River Neck Road (State Road S-26-236) and go
6.3 km (3.9 mi) to the entrance gate of Tilghman Point. Check with caretaker at
the first house on the left for permission to enter. The bench marks are about
2.01 km (1.25 mi) NE of the entrance gate on the south side of a dirt road
leading to Little River. The tide gage and staff were on Dunn Sound about 2.1
km (1.3 mi) NE of the entrance gate, and SE of bench mark LRN NO 1 1975.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: LRN NO 1 1975
DESIGNATION: 866 0147 TIDAL LRN 1
MONUMENTATION: Tidal Station disk VM#: 3674
AGENCY: National Ocean Survey (NOS) IDB PID#: DD1738
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 33° 51.6' N ( 33.86000) LONGITUDE: 78° 34.9' W ( -78.58170)
The primary bench mark is a disk located 2.0 km (1.3 mi) NW of the entrance gate
on the south side of the dirt road where the creek bank is nearest to the road,
10 m (33 ft) NW of the embankment, 6 m (20 ft) SE of the centerline of the road,
and 3 m (10 ft) north of a hickory tree stump projecting 1 m (2 ft) above the
ground. The bench mark is set 6 cm (0.2 ft) below ground level, crimped to the
top of a copper-clad steel rod driven an unspecified depth, and encased in a
4-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8660147 PUBLICATION DATE: 05/20/2004
Name: DUNN SOUND, NORTH, LITTLE RIVER
SC
NOAA Chart: 11535 Latitude: 33° 51.6' N ( 33.86000)
USGS Quad: LITTLE RIVER Longitude: 78° 34.8' W ( -78.58000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LRN NO 2 1975
DESIGNATION: 866 0147 TIDAL LRN 2
MONUMENTATION: Tidal Station disk VM#: 3675
AGENCY: National Ocean Survey (NOS) IDB PID#: DD1739
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 33° 51.6' N ( 33.86000) LONGITUDE: 78° 34.8' W ( -78.58000)
The bench mark is a disk located on the south side of the dirt road, 25 m (82
ft) NE of bench mark LRN NO 1 1975, 8 m (27 ft) NW of the embankment, 7 m (24
ft) SE of the centerline of the road, and 2.29 m (7.5 ft) west of a large forked
pine tree. The bench mark is set at ground level, crimped to the top of a
copper-clad steel rod driven an unspecified depth, and encased in a 4-inch PVC
pipe and concrete kickblock.
BENCH MARK STAMPING: LRN NO 3 1975
DESIGNATION: 866 0147 TIDAL LRN 3
MONUMENTATION: Tidal Station disk VM#: 3676
AGENCY: National Ocean Survey (NOS) IDB PID#: DD1740
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 33° 51.7' N ( 33.86170) LONGITUDE: 78° 34.7' W ( -78.57830)
The bench mark is a disk located on the south side of the dirt road, 119 m (390
ft) NE of bench mark LRN NO 2 1975, 10.49 m (34.4 ft) SE of the centerline of
the road, and 6 m (19 ft) west of a forked oak tree. The bench mark is set 9 cm
(0.3 ft) below ground level, crimped to the top of a copper-clad steel rod
driven an unspecified depth, and encased in a 4-inch PVC pipe and concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8660147 PUBLICATION DATE: 05/20/2004
Name: DUNN SOUND, NORTH, LITTLE RIVER
SC
NOAA Chart: 11535 Latitude: 33° 51.6' N ( 33.86000)
USGS Quad: LITTLE RIVER Longitude: 78° 34.8' W ( -78.58000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LRN NO 4 1975
DESIGNATION: 866 0147 TIDAL LRN 4
MONUMENTATION: Tidal Station disk VM#: 3677
AGENCY: National Ocean Survey (NOS) IDB PID#: DD1741
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 33° 51.7' N ( 33.86170) LONGITUDE: 78° 34.7' W ( -78.57830)
The bench mark is a disk set in the top of a concrete monument on the south side
of the dirt road, 59 m (195 ft) NE of bench mark LRN NO 3 1975, 27 m (90 ft)
north of two oak trees leaning in opposite directions, 24 m (78 ft) west of the
road leading to Tilghmans summer house, 9 m (31 ft) SE of the centerline of the
road, and at ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8660147 PUBLICATION DATE: 05/20/2004
Name: DUNN SOUND, NORTH, LITTLE RIVER
SC
NOAA Chart: 11535 Latitude: 33° 51.6' N ( 33.86000)
USGS Quad: LITTLE RIVER Longitude: 78° 34.8' W ( -78.58000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: 866 0147 BM 5
ALIAS: NO STAMPING 1
MONUMENTATION: Chiseled Square VM#: 3678
AGENCY: Unknown IDB PID#:
SETTING CLASSIFICATION: Concrete and brick monument OPUS PID:
LATITUDE: 33° 51.6' N ( 33.86000) LONGITUDE: 78° 34.8' W ( -78.58000)
The bench mark is an inch square chiseled mark in the NE corner of a 0.37 m (1.2
ft) square concrete and brick monument with small nails spelling out HURRICANE
HAZEL WATER LEVEL OCT 1954, about 2.6 km (1.6 mi) NE of the entrance gate, 151 m
(495 ft) SE of bench mark LRN NO 4 1975, 35 m (115 ft) south of the SW corner of
Tilghmans summer house, 2.29 m (7.5 ft) NE of the embankment, and 9 cm (0.3 ft)
above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8660147 PUBLICATION DATE: 05/20/2004
Name: DUNN SOUND, NORTH, LITTLE RIVER
SC
NOAA Chart: 11535 Latitude: 33° 51.6' N ( 33.86000)
USGS Quad: LITTLE RIVER Longitude: 78° 34.8' W ( -78.58000)
T I D A L D A T U M S
Tidal datums at DUNN SOUND, NORTH, LITTLE RIVER based on:
LENGTH OF SERIES: 1 YEAR
TIME PERIOD: January 1975 - December 1975
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8665530 CHARLESTON, COOPER RIVER ENTRANCE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (11/12/1974) = 2.117
MEAN HIGHER HIGH WATER MHHW = 1.592
MEAN HIGH WATER MHW = 1.473
North American Vertical Datum NAVD88 = 0.864
MEAN SEA LEVEL MSL = 0.766
MEAN TIDE LEVEL MTL = 0.761
MEAN LOW WATER MLW = 0.049
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/01/1976) = -0.483
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
LRN NO 1 1975 9.908 8.435
LRN NO 2 1975 9.998 8.525
LRN NO 3 1975 7.390 5.917
LRN NO 4 1975 8.889 7.416
866 0147 BM 5 5.291 3.818
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8660147 PUBLICATION DATE: 05/20/2004
Name: DUNN SOUND, NORTH, LITTLE RIVER
SC
NOAA Chart: 11535 Latitude: 33° 51.6' N ( 33.86000)
USGS Quad: LITTLE RIVER Longitude: 78° 34.8' W ( -78.58000)
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.