U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
PUBLICATION DATE: 03/26/1984
Station ID: 8666101 SUPERCEDED DATE: 04/21/2003
Name: JOHN ISLAND, CHURCH CREEK
SOUTH CAROLINA
NOAA Chart: 11522 Latitude: 32° 42.4' N
USGS Quad: WADMALAW ISLAND Longitude: 80° 9.4' W
To reach the tidal bench marks from intersection of Maybank Highway (S.C.
Highway 700) and Bohicket Road (S.C. Highway 20), proceed north on S.C. Highway
20 for 1.1 miles (1.8 km), past Johns Island High School, left on county road 54
for 4.3 miles (6.9 km) to driveway on left, Dr. R.R. Doss residence, then along
dirt driveway for 1.1 miles (1.8 km) to house. The bench marks are located in
the vicinity of the Doss residence and extend NE along the driveway. Tide gage
and staff were located on pier behind house.
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#: 4250
AGENCY: PID#: CK2635
SETTING CLASSIFICATION: Concrete Monument
The bench mark is at ground level, set in a concrete filled tile pipe, at the
shore end of the pier, 135.1 feet (41.2 m) ESE of south corner of steps leading
to Doss house, 33.0 feet (10.1 m) NW of first piling on land end of dock, 12.0
feet (3.7 m) WSW of centerline of path leading to dock and 10.7 feet (3.3 m)
north of a 1.5 feet (0.5 m) diameter laurel oak.
BENCH MARK STAMPING: NO 2 1934
MONUMENTATION: Survey Disk VM#: 4251
AGENCY: PID#: CK2634
SETTING CLASSIFICATION: Concrete Monument
The bench mark is at ground level, set flush in a concrete filled tile pipe, on
lawn east of pier, 85.3 feet (26.0 m) NE of Bench Mark NO 1 1934, 81.4 feet
(24.8 m) ESE of Bench Mark NO 7 1974, 55.0 feet (16.8 m) NNE of 1.3 feet (0.4 m)
diameter palmetto tree.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
PUBLICATION DATE: 03/26/1984
Station ID: 8666101 SUPERCEDED DATE: 04/21/2003
Name: JOHN ISLAND, CHURCH CREEK
SOUTH CAROLINA
NOAA Chart: 11522 Latitude: 32° 42.4' N
USGS Quad: WADMALAW ISLAND Longitude: 80° 9.4' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 4 1954
MONUMENTATION: Survey Disk VM#: 4252
AGENCY: PID#: CK2633
SETTING CLASSIFICATION: Concrete Monument
The bench mark is at ground level, set flush in a concrete monument, north of
picnic area, 127.7 feet (38.9 m) east of Bench Mark NO 7 1974, 63.9 feet (19.5
m) NE of Bench Mark NO 2 1934, 42.5 feet (13.0 m) west of northernmost light
pole in picnic area, and 4.5 feet (1.4 m) WNW of 1.6 feet (0.5 m) diameter oak
tree.
BENCH MARK STAMPING: NO 6 1974
MONUMENTATION: Survey Disk VM#: 4253
AGENCY: PID#: CK2638
SETTING CLASSIFICATION: Concrete Monument
The bench mark is at ground level set flush in a concrete monument, between
three trees just south of drive leading to Doss house, 95.3 feet (29.0 m) NW of
Bench Mark NO 4 1954, 80.0 feet (24.4 m) south of easternmost cedar tree
flanking drive, 71.1 feet (21.7 m) ENE of northern corner of concrete pump
house, and 69.0 feet (21.0 m) ESE of centerline of drive leading to Doss
residence.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
PUBLICATION DATE: 03/26/1984
Station ID: 8666101 SUPERCEDED DATE: 04/21/2003
Name: JOHN ISLAND, CHURCH CREEK
SOUTH CAROLINA
NOAA Chart: 11522 Latitude: 32° 42.4' N
USGS Quad: WADMALAW ISLAND Longitude: 80° 9.4' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 7 1974
MONUMENTATION: Survey Disk VM#: 4254
AGENCY: PID#: CK2636
SETTING CLASSIFICATION: Concrete Monument
The bench mark is at ground level, set flush in a concrete monument, east of
north corner of concrete patio slab, 92.4 feet (28.2 m) SSW of Bench Mark NO 6
1974, 58.3 feet (17.8 m) ENE of east corner of Doss house, 49.1 feet (15.0 m)
SSE of East corner of concrete pump house, and 1.9 feet (0.6 m) east of north
corner of concrete patio pad.
BENCH MARK STAMPING: 6101 F 1977
MONUMENTATION: Survey Disk VM#: 4255
AGENCY: PID#: CK2637
SETTING CLASSIFICATION: Copper-Clad Steel Rod
The bench mark is located on north side of drive leading to Doss house, 162.0
feet (49.4 m) north of Bench Mark NO 6 1974, 68.5 feet (20.9 m) ENE of 4.2 feet
(1.3 m) oak tree, 37.0 feet (11.3 m) WNW of centerline of dirt drive, and 23.6
feet (7.2 m) west of westernmost cedar flanking drive. The bench mark is at
ground level, crimped to the top of a copper-clad steel rod driven 3.4 feet (10
m) to refusal, encased in a 4-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
PUBLICATION DATE: 03/26/1984
Station ID: 8666101 SUPERCEDED DATE: 04/21/2003
Name: JOHN ISLAND, CHURCH CREEK
SOUTH CAROLINA
NOAA Chart: 11522 Latitude: 32° 42.4' N
USGS Quad: WADMALAW ISLAND Longitude: 80° 9.4' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6101 G 1977
MONUMENTATION: Survey Disk VM#: 4256
AGENCY: PID#: CK2632
SETTING CLASSIFICATION: Copper-Clad Steel Rod
The bench mark is located south of drive leading to Doss House, 285.0 feet (86.9
m) NNE of Bench Mark 6101 F 1977, 23.0 feet (7.0 m) ESE of second power pole
north of house, 15 feet ( 5 m) from fourth crepe myrtle tree from (on east side
of road). The bench mark is at ground level crimped to the top of a copper-clad
steel rod driven 32 feet (10 m) to refusal, encased in 4-inch PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 6101 H 1977
MONUMENTATION: Survey Disk VM#: 4257
AGENCY: PID:
SETTING CLASSIFICATION: Copper-Clad Steel Rod
The bench mark is located just north of drive leading to Doss House, 276 feet
(84 m) north of Bench Mark 6101 G 1977,125.5 feet (38.2 m) SSW of third power
pole from house and 21.0 feet (6.4 m) WNW of centerline of road. The bench mark
is at ground level crimped to the top of a copper clad steel rod, driven 28 feet
(9 m) to refusal, encased in a 4-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
PUBLICATION DATE: 03/26/1984
Station ID: 8666101 SUPERCEDED DATE: 04/21/2003
Name: JOHN ISLAND, CHURCH CREEK
SOUTH CAROLINA
NOAA Chart: 11522 Latitude: 32° 42.4' N
USGS Quad: WADMALAW ISLAND Longitude: 80° 9.4' W
T I D A L D A T U M S
Tidal datums at JOHN ISLAND, CHURCH CREEK based on:
LENGTH OF SERIES: 1 YEAR
TIME PERIOD: FEBRUARY 1977-JANUARY 1978
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 (06/01/1977) = 9.27
MEAN HIGHER HIGH WATER MHHW = 7.47
MEAN HIGH WATER MHW = 7.14
MEAN TIDE LEVEL MTL = 3.68
MEAN LOW WATER MLW = 0.22
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (01/09/1978) = -2.72
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1934 13.96 6.82
NO 2 1934 16.34 9.20
NO 4 1954 16.02 8.88
NO 6 1974 19.43 12.29
NO 7 1974 19.42 12.28
6101 F 1977 18.55 11.41
6101 G 1977 17.51 10.37
6101 H 1977 17.06 9.92
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
PUBLICATION DATE: 03/26/1984
Station ID: 8666101 SUPERCEDED DATE: 04/21/2003
Name: JOHN ISLAND, CHURCH CREEK
SOUTH CAROLINA
NOAA Chart: 11522 Latitude: 32° 42.4' N
USGS Quad: WADMALAW ISLAND Longitude: 80° 9.4' 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.