U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 05/02/1989
Station ID: 8664841 SUPERCEDED DATE: 04/21/2003
Name: MAGNOLIA GARDENS, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 52.6' N
USGS Quad: LADSON Longitude: 80° 4.9' W
To reach the tidal bench marks from the intersection of State Highway 61 and
State Highway 7 in Charleston, proceed north on State Highway 61 for 6.5 miles
(10.5 km), turn right into Magnolia Gardens Plantation & Nursery, travel down a
dirt road for 0.2 mile (0.3 km) to a fork in the road, follow the Trucks and
Nursery signs for 0.4 mile (0.6 km), turn left on a dirt road near the equipment
depot and go 0.1 mile (0.2 km) to the main hot house, follow a dirt path to the
right of the hot house for about 180 feet (55 m) to a foot bridge and a short
dock. The bench marks are near the dock and along the foot path. The tide gage
and staff were on the end of the short dock.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1934
MONUMENTATION: Survey Disk VM#: 4104
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument, 70.0 feet (21.3 m) SE of
Bench Mark N0 2 1934, 36.5 feet (11.1 m) NE of an unnumbered utility pole
approximately 8 feet (2 m) west of the top of a bluff, 5.5 feet (1.7 m) east of
the NE gate post, 4.5 feet (1.4 m) south of a fenceline, and 0.3 foot (0.1 m)
above ground level.
BENCH MARK STAMPING: NO 2 1934
MONUMENTATION: Survey Disk VM#: 4105
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument, 61.0 feet (18.6 m) SSE of
the SE corner of a lake, 28.8 feet (8.8 m) west of the center of the top stair
leading to the dock, 27.3 feet (8.3 m) south of the NE top corner of the granite
memorial to Henry Woodward, 4.7 feet (1.4 m) SW of the center of a dirt walk,
and 0.6 foot (0.2 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 05/02/1989
Station ID: 8664841 SUPERCEDED DATE: 04/21/2003
Name: MAGNOLIA GARDENS, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 52.6' N
USGS Quad: LADSON Longitude: 80° 4.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1934
MONUMENTATION: Survey Disk VM#: 4106
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument in a clump of bushes, 125.0
feet (38.1 m) NE of Bench Mark N0 2 1934, 25.0 feet (7.6 m) east of the east
edge of a path along the north end of a lake, 21.0 feet (6.4 m) south of the
edge of a path along the north end of the lake, 15.0 feet (4.6 m) south of the
face of a 1.1 foot (0.3 m) diameter red cedar tree, 8.6 feet (2.6 m) west of the
river bank, 3 feet (1 m) below the level of a foot path and 0.2 foot (0.1
m) below ground level,
BENCH MARK STAMPING: NO 4 1974
MONUMENTATION: Survey Disk VM#: 4107
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument, 100.3 feet (30.6 m) NE of
the NE corner of a greenhouse and Bench Mark N0 5 1974, 53.0 feet (16.2 m) south
of a fence, 49.0 feet (14.9 m) SE of Bench Mark N0 1 1934, 43.0 feet (13.1 m)
ESE of an unnumbered utility pole 11.1 feet (3.4 m) SW of the top of a bluff,
and 1.5 feet (0.5 m) below a dirt and plant dumping ground for the nursery.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 05/02/1989
Station ID: 8664841 SUPERCEDED DATE: 04/21/2003
Name: MAGNOLIA GARDENS, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 52.6' N
USGS Quad: LADSON Longitude: 80° 4.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1974
MONUMENTATION: Survey Disk VM#: 4108
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument, 128.8 feet (39.3 m) south of
Bench Mark N0 1 1934, 42.5 feet (13.0 m) NW of a 5 foot (2 m) diameter birch
tree, 1.1 feet (0.3 m) ENE of the NE corner of a greenhouse, and level with the
ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 05/02/1989
Station ID: 8664841 SUPERCEDED DATE: 04/21/2003
Name: MAGNOLIA GARDENS, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 52.6' N
USGS Quad: LADSON Longitude: 80° 4.9' W
T I D A L D A T U M S
Tidal datums at MAGNOLIA GARDENS, ASHLEY RIVER based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: AUGUST - NOVEMBER 1982
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8665530 CHARLESTON
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (11/04/1982) = 7.44
MEAN HIGHER HIGH WATER MHHW = 6.27
MEAN HIGH WATER MHW = 5.99
MEAN TIDE LEVEL MTL = 3.10
MEAN LOW WATER MLW = 0.20
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/02/1982) = -0.70
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1934 15.92 9.93
NO 2 1934 14.09 8.10
NO 3 1934 8.03 2.04
NO 4 1974 15.15 9.16
NO 5 1974 16.46 10.47
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 05/02/1989
Station ID: 8664841 SUPERCEDED DATE: 04/21/2003
Name: MAGNOLIA GARDENS, ASHLEY RIVER
SOUTH CAROLINA
NOAA Chart: 11521 Latitude: 32° 52.6' N
USGS Quad: LADSON Longitude: 80° 4.9' 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.