U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8665552 PUBLICATION DATE: 07/21/2003
Name: BREACH INLET
SC
NOAA Chart: 11523 Latitude: 32° 46.6' N ( 32.77670)
USGS Quad: FORT MOULTRIE Longitude: 79° 48.7' W ( -79.81170)
To reach the tidal bench marks from Sullivans Island, proceed NE on State
Highway 703 to William Thompson Memorial Bridge over Breach Inlet. The bench
marks are at both ends of the bridge. The tide gage and staff were on the north
side of the bridge near the Isle of Palms end.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: BREACH NO 1 1963
DESIGNATION: BREACH RM 1
MONUMENTATION: Reference Mark disk VM#: 4190
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: CJ0605
SETTING CLASSIFICATION: Sidewalk OPUS PID:
LATITUDE: 32° 46.5' N ( 32.77500) LONGITUDE: 79° 48.8' W ( -79.81330)
The primary bench mark is a disk set in the south sidewalk near the SW end of
the bridge over Breach Inlet, 13.93 m (45.7 ft) NNE of the William Thompson
Memorial Monument, 13.26 m (43.5 ft) NE of the SW end of the bridge, 4.57 m
(15.0 ft) SE of the centerline of the highway, and 0.64 m (2.1 ft) NW of the
guard rail.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8665552 PUBLICATION DATE: 07/21/2003
Name: BREACH INLET
SC
NOAA Chart: 11523 Latitude: 32° 46.6' N ( 32.77670)
USGS Quad: FORT MOULTRIE Longitude: 79° 48.7' W ( -79.81170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BREACH NO 2 1963
DESIGNATION: BREACH RM 2
MONUMENTATION: Reference Mark disk VM#: 4191
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: CJ0606
SETTING CLASSIFICATION: Sidewalk OPUS PID:
LATITUDE: 32° 46.5' N ( 32.77500) LONGITUDE: 79° 48.8' W ( -79.81330)
The bench mark is a disk set in the north sidewalk of the SW end of the bridge
over Breach Inlet, 4.27 m (14.0 ft) NW of the centerline of the highway, 0.91 m
(3.0 ft) SE of the NW corner of the bridge, and 0.76 m (2.5 ft) NW of the curb.
BENCH MARK STAMPING: BI NO 3 1975
DESIGNATION: 866 5552 TIDAL BI 3
MONUMENTATION: Tidal Station disk VM#: 4192
AGENCY: National Ocean Survey (NOS) IDB PID#: CJ0607
SETTING CLASSIFICATION: Concrete abutment OPUS PID:
LATITUDE: 32° 46.6' N ( 32.77670) LONGITUDE: 79° 48.6' W ( -79.81000)
The bench mark is a disk set in the north concrete abutment on the NE end of the
bridge over Breach Inlet, 9.54 m (31.3 ft) NE of a metal light pole, 6 m (20 ft)
NW of the centerline of the highway, and 1.22 m (4.0 ft) SW of the Willian
Thompson Memorial Bridge concrete sign.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8665552 PUBLICATION DATE: 07/21/2003
Name: BREACH INLET
SC
NOAA Chart: 11523 Latitude: 32° 46.6' N ( 32.77670)
USGS Quad: FORT MOULTRIE Longitude: 79° 48.7' W ( -79.81170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BI NO 4 1975
DESIGNATION: 866 5552 TIDAL BI 4
MONUMENTATION: Tidal Station disk VM#: 4193
AGENCY: National Ocean Survey (NOS) IDB PID#: CJ0608
SETTING CLASSIFICATION: Concrete abutment OPUS PID:
LATITUDE: 32° 46.6' N ( 32.77670) LONGITUDE: 79° 48.6' W ( -79.81000)
The bench mark is a disk set in the south concrete abutment on the NE end of the
bridge over Breach Inlet, 24.69 m (81.0 ft) west of power pole #71478, and 5.97
m (19.6 ft) SE of the centerline of the highway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8665552 PUBLICATION DATE: 07/21/2003
Name: BREACH INLET
SC
NOAA Chart: 11523 Latitude: 32° 46.6' N ( 32.77670)
USGS Quad: FORT MOULTRIE Longitude: 79° 48.7' W ( -79.81170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BREACH 1963
DESIGNATION: BREACH
MONUMENTATION: Triangulation Station disk VM#: 17120
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: CJ0604
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 32° 46.5' N ( 32.77500) LONGITUDE: 79° 48.8' W ( -79.81330)
The bench mark is a disk set into the top of a square concrete monument 0.25 m
(0.8 ft) on a side recessed 0.24 m (0.8 ft) below the ground, south of the SW
end of the bridge, 9.41 m (30.9 ft) SE from the approximate center of State
Highway 703, 8.75 m (28.7 ft) east from the approximate center of a bell system
man hole cover, 3.95 m (12.95 ft) south from the SW end of the bridge and 2.61 m
(8.55 ft) south from a power pole with one guy wire.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8665552 PUBLICATION DATE: 07/21/2003
Name: BREACH INLET
SC
NOAA Chart: 11523 Latitude: 32° 46.6' N ( 32.77670)
USGS Quad: FORT MOULTRIE Longitude: 79° 48.7' W ( -79.81170)
T I D A L D A T U M S
Tidal datums at BREACH INLET based on:
LENGTH OF SERIES: 12 MONTHS
TIME PERIOD: June 1975 - May 1976
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 (06/10/1975) = 2.159
MEAN HIGHER HIGH WATER MHHW = 1.680
MEAN HIGH WATER MHW = 1.565
North American Vertical Datum NAVD88 = 0.947
MEAN SEA LEVEL MSL = 0.827
MEAN TIDE LEVEL MTL = 0.812
MEAN LOW WATER MLW = 0.060
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (12/21/1976) = -1.008
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
BREACH NO 1 1963 4.509 2.944
BREACH NO 2 1963 4.523 2.958
BI NO 3 1975 4.525 2.960
BI NO 4 1975 4.519 2.954
BREACH 1963 4.278 2.713
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8665552 PUBLICATION DATE: 07/21/2003
Name: BREACH INLET
SC
NOAA Chart: 11523 Latitude: 32° 46.6' N ( 32.77670)
USGS Quad: FORT MOULTRIE Longitude: 79° 48.7' W ( -79.81170)
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.