U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
To reach the tide station from the intersection of US-17 (Church St) and US-701
(N Fraser St) in Georgetown, SC head SW on Fraser St for 1.8 km (1.1 mi) to the
entrance for the Port of Georgetown at Dock St and turn left. Proceed east on
Dock St for 0.8 km (0.5 mi) to the large dock warehouse and turn right to head
SE towards the main dock. Proceed for 106 m (350 ft) to the dock's edge and
turn left along the water, proceeding NE for 155 m (510 ft) to the end of the
dock. The tide station is located on the east corner of the main dock. The
bench marks are located within the port facility and along US-17.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2926 F 2022
DESIGNATION: 866 2926 F
MONUMENTATION: Tidal Station disk VM#: 24196
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete pier OPUS PID#: BBHS49
LATITUDE: 33° 21.6' N ( 33.36039) LONGITUDE: 79° 17.2' E ( 79.28634)
The primary bench mark is located 19.70 m (64.6 ft) ESE of the SE corner of the
port warehouse, 15.10 m (49.5 ft) SW of the east corner of the pier, 0.45 m (1.5
ft) SE of the second bollard west from the east end of the pier, and 0.49 m (1.6
ft) NW of the SE edge of the wood cribbing.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: GT A 2014
DESIGNATION: GT A
MONUMENTATION: Survey disk VM#: 24197
AGENCY: South Carolina Geodetic Survey (SCGS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID#: DP8974
LATITUDE: 33° 21.7' N ( 33.36119) LONGITUDE: 79° 17.7' E ( 79.29436)
The bench mark is a concrete post flush with the ground and 15.00 cm (6 inches)
below the road, 30.10 m (98.8 ft) west of the west end of a triangular concrete
median, 27.60 m (90.6 ft) WSW of the west leg of a wood sign (southern loggers
cooperative), 23.80 m (78.1 ft) SSW of the east end of a 1.2-ft concrete pipe
culvert for a retaining pond, 11.70 m (38.4 ft) SW of the center of the road,
9.80 m (32.2 ft) NE of the NE rail of a railroad track, and 1.00 m (3.3 ft)
north of a witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: D 125 RESET 1985
DESIGNATION: D 125 RESET
MONUMENTATION: Bench Mark disk VM#: 24198
AGENCY: National Geodetic Survey (NGS) IDB PID#:
SETTING CLASSIFICATION: Wingwall of bridge OPUS PID:
LATITUDE: 33° 21.8' N ( 33.36286) LONGITUDE: 79° 17.7' E ( 79.29553)
The bench mark is a brass disk set in 0.30 m (1.0 ft) above the highway in the
NW wingwall of the bridge over the Sampit river , located 5.80 m (19.0 ft) west
of the centerline of the two southbound lanes of the highway, 0.7 m (2.3 ft)
east of the west edge of the wing wall, 0.27m (0.9 ft) north of a street light
pole, and 0.27m (0.9 ft) south of the Sampit river sign.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: GEORGE NO 1 1962
DESIGNATION: GEORGE RM 1
MONUMENTATION: Reference Mark disk VM#: 24199
AGENCY: U.S Coast Geodetic Survey (CGS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 33° 21.3' N ( 33.35513) LONGITUDE: 79° 17.3' E ( 79.28871)
The bench mark is a brass disk is located 23.20 m (76.1 ft) NNE of triangulation
station George, 20.10 m (65.9 ft) SW of the center of prince street, 14.70 m
(48.2 ft) SW of a utility light pole, 12.60 m (41.3 ft) NW of the center of
dozier street, 9.90 m (32.5 ft) SE of a 10-inch pine tree, and 2.30 m (7.5 ft)
NNW of a manhole cover. The bench mark set in a concrete monument recessed 0.10
m (0.3 ft) below the ground surface and 0.30 m (1.0 ft) below the level of
dozier street.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: E 125 1962
DESIGNATION: E 125
MONUMENTATION: Bench Mark disk VM#: 24200
AGENCY: U.S Coast & Geodetic Survey ( CGS) IDB PID#:
SETTING CLASSIFICATION: Building OPUS PID:
LATITUDE: 33° 22.6' N ( 33.37657) LONGITUDE: 79° 17.2' E ( 79.28732)
The bench mark is brass disk set vertically in the west face of the SW corner
brick wall about 0.8 m (2.5 ft) above the ground surface, located 35.50 m (116.5
ft) east of the center of the center turning lane of U.S. highway 701, 26.40 m
(86.6 ft) south of the main entrance door to the sheriff's office on the west
side of the building, and 0.40 m (1.3 ft) north of the SW corner of the
building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
T I D A L D A T U M S
Tidal datums at GEORGETOWN, SAMPIT RIVER ENT. based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: March 2022 - June 2022
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:
MEAN HIGHER HIGH WATER MHHW = 1.290
MEAN HIGH WATER MHW = 1.218
North American Vertical Datum NAVD88 = 0.669
MEAN SEA LEVEL MSL = 0.667
MEAN TIDE LEVEL MTL = 0.636
MEAN LOW WATER MLW = 0.053
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2926 F 2022 3.856 2.638
GT A 2014 3.329 2.111
D 125 RESET 1985 7.675 6.457
GEORGE NO 1 1962 2.126 0.908
E 125 1962 5.758 4.540
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8662926 PUBLICATION DATE: 06/28/2023
Name: GEORGETOWN, SAMPIT RIVER ENT.
SC
NOAA Chart: 11532 Latitude: 33° 21.6' N ( 33.36056)
USGS Quad: GEORGETOWN SOUTH Longitude: 79° 17.2' W ( -79.28611)
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.