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National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8665814 PUBLICATION DATE: 11/23/2005
Name: ASHEPOO RIVER AT 17
SC
NOAA Chart: 11517 Latitude: 32° 44.6' N ( 32.74330)
USGS Quad: Green Pond Longitude: 80° 33.4' W ( -80.55670)
To reach the tidal bench marks from the intersection of U.S. Highway 17 and
State Road 64 at Jacksonboro, proceed WSW on State Road 64 for 8.0 km (5.0 mi)
to the road bridge over the Ashepoo River. The bench marks are on the west side
of the Ashepoo River, along U.S. Highway 17, and on the bridge. The tide gage
and staff were on the west side of the river, just south of the bridge, near the
private boat landing owned by Mr. Smith (Smith's Landing).
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5814 A 1977
DESIGNATION: 866 5814 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 4236
AGENCY: National Ocean Survey (NOS) IDB PID#: CK3003
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 32° 44.6' N ( 32.74330) LONGITUDE: 80° 33.4' W ( -80.55670)
The primary bench mark is a disk located at Smith's Landing, 29.23 m (96.0 ft)
SE of bench mark 5814 B 1977, 17.37 m (57.0 ft) WNW of the centerline of the
concrete boat landing, 16.46 m (54.0 ft) NNE of SCE&G power pole #205484 and 4 m
(12 ft) SSW of the river bank. The bench mark is set at ground level, crimped
to the top of a copper-clad steel rod driven 4.9 m (16 ft) to refusal, 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 5
Station ID: 8665814 PUBLICATION DATE: 11/23/2005
Name: ASHEPOO RIVER AT 17
SC
NOAA Chart: 11517 Latitude: 32° 44.6' N ( 32.74330)
USGS Quad: Green Pond Longitude: 80° 33.4' W ( -80.55670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5814 B 1977
DESIGNATION: 866 5814 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 4237
AGENCY: National Ocean Survey (NOS) IDB PID#: CK3002
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 32° 44.6' N ( 32.74330) LONGITUDE: 80° 33.4' W ( -80.55670)
The bench mark is a disk located along U.S. Highway 17 at the utility pole
closest to the Ashepoo River, 23.16 m (76.0 ft) NW of SCE&G power pole #205484,
22 m (72 ft) NE of a 1 m (2 ft) diameter pine tree, 20.57 m (67.5 ft) SSE of the
centerline of U.S. highway 17, 18.59 m (61.0 ft) ESE of the SW corner of the
bridge, and 1.89 m (6.2 ft) ESE of utility pole #4939. The bench mark is set at
ground level, crimped to the top of an unspecified steel rod driven an
unspecified depth, and surrounded by a kickblock.
BENCH MARK STAMPING: 5814 G 1981
DESIGNATION: 866 5814 G TIDAL
MONUMENTATION: Tidal Station disk VM#: 4238
AGENCY: National Ocean Survey (NOS) IDB PID#: CK3000
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 32° 44.6' N ( 32.74330) LONGITUDE: 80° 33.4' W ( -80.55670)
The bench mark is a disk set in the top of a concrete monument along U.S.
Highway 17, 111 m (364 ft) SW of bench mark 5814 B 1977, 19 m (62 ft) SSE of the
centerline of U.S. Highway 17, 1.43 m (4.7 ft) SW of telephone junction box
#A79261, and 0.12 m (0.4 ft) above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8665814 PUBLICATION DATE: 11/23/2005
Name: ASHEPOO RIVER AT 17
SC
NOAA Chart: 11517 Latitude: 32° 44.6' N ( 32.74330)
USGS Quad: Green Pond Longitude: 80° 33.4' W ( -80.55670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5814 H 1981
DESIGNATION: 866 5814 H TIDAL
MONUMENTATION: Tidal Station disk VM#: 4239
AGENCY: National Ocean Survey (NOS) IDB PID#: CK3001
SETTING CLASSIFICATION: Concrete bridge abutment OPUS PID:
LATITUDE: 32° 44.6' N ( 32.74330) LONGITUDE: 80° 33.4' W ( -80.55670)
The bench mark is a disk set flush in the concrete bridge abutment of the U.S.
Highway 17 bridge over the Ashepoo River, 5.58 m (18.3 ft) NNE of the centerline
of U.S. Highway 17, 5.06 m (16.6 ft) ENE of a guy wire anchor to power pole
#30PL18, 3.38 m (11.1 ft) SE of power pole #30PL18, and 0.55 m (1.8 ft) WNW of
the SW corner of the bridge rail.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8665814 PUBLICATION DATE: 11/23/2005
Name: ASHEPOO RIVER AT 17
SC
NOAA Chart: 11517 Latitude: 32° 44.6' N ( 32.74330)
USGS Quad: Green Pond Longitude: 80° 33.4' W ( -80.55670)
T I D A L D A T U M S
Tidal datums at ASHEPOO RIVER AT 17 based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: May 1981 - October 1981
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 = 0.767
MEAN HIGH WATER MHW = 0.742
MEAN SEA LEVEL MSL = 0.479
MEAN TIDE LEVEL MTL = 0.412
North American Vertical Datum NAVD88 = 0.299
MEAN LOW WATER MLW = 0.083
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
5814 A 1977 1.864 1.122
5814 B 1977 1.843 1.101
5814 G 1981 1.964 1.222
5814 H 1981 3.876 3.134
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8665814 PUBLICATION DATE: 11/23/2005
Name: ASHEPOO RIVER AT 17
SC
NOAA Chart: 11517 Latitude: 32° 44.6' N ( 32.74330)
USGS Quad: Green Pond Longitude: 80° 33.4' W ( -80.55670)
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.
Station Location
Published bench mark
Unpublished bench mark
