U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8666101 PUBLICATION DATE: 02/05/2004
Name: JOHNS 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 1.8 km (1.1 mi), past Johns Island High School, left on county road 54
for 6.9 km (4.3 mi) to driveway on left, Dr. R.R. Doss residence, then along
dirt driveway for 1.8 km (1.1 mi) 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
DESIGNATION: 866 6101 TIDAL 1
ALIAS: TIDAL 1 STA 66
MONUMENTATION: Tidal Station disk VM#: 4250
AGENCY: US Coast and Geodetic Survey (USC&GS) PID#: CK2635
SETTING CLASSIFICATION: Concrete filled tile pipe
The primary bench mark is a disk set in a concrete filled tile pipe at the shore
end of the pier, 41.18 m (135.1 ft) ESE of south corner of steps leading to Doss
house, 10 m (33 ft) NW of first piling on land end of dock, 3.66 m (12.0 ft) WSW
of centerline of path leading to dock and 3.26 m (10.7 ft) north of a 0.46 m
(1.5 ft) diameter laurel oak.
BENCH MARK STAMPING: NO 2 1934
DESIGNATION: 866 6101 TIDAL 2
ALIAS: TIDAL 2 STA 66
MONUMENTATION: Tidal Station disk VM#: 4251
AGENCY: US Coast and Geodetic Survey (USC&GS) PID#: CK2634
SETTING CLASSIFICATION: Concrete and tile monument
The bench mark is a disk set flush in a concrete and tile monument on a lawn
east of pier, 26.00 m (85.3 ft) NE of bench mark NO 1 1934, 24.81 m (81.4 ft)
ESE of bench mark NO 7 1974, 16.76 m (55.0 ft) NNE of 0.40 m (1.3 ft) diameter
palmetto tree.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8666101 PUBLICATION DATE: 02/05/2004
Name: JOHNS 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
DESIGNATION: 866 6101 TIDAL 4
ALIAS: TIDAL 4 STA 66
MONUMENTATION: Tidal Station disk VM#: 4252
AGENCY: US Coast and Geodetic Survey (USC&GS) PID#: CK2633
SETTING CLASSIFICATION: Concrete monument
The bench mark is a disk set flush in a concrete monument north of picnic area,
38.92 m (127.7 ft) east of bench mark NO 7 1974, 19.48 m (63.9 ft) NE of bench
mark NO 2 1934, 12.95 m (42.5 ft) west of northernmost light pole in picnic
area, and 1.37 m (4.5 ft) WNW of 0.49 m (1.6 ft) diameter oak tree.
BENCH MARK STAMPING: NO 6 1974
DESIGNATION: 866 6101 TIDAL 6
MONUMENTATION: Tidal Station disk VM#: 4253
AGENCY: National Ocean Survey (NOS) PID#: CK2638
SETTING CLASSIFICATION: Concrete monument
The bench mark is a disk set flush in a concrete monument, between three trees
just south of drive leading to Doss house, 29.05 m (95.3 ft) NW of bench mark NO
4 1954, 24.38 m (80.0 ft) south of easternmost cedar tree flanking drive, 21.67
m (71.1 ft) ENE of northern corner of concrete pump house, 21 m (69 ft) ESE of
centerline of drive leading to Doss residence, and at ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8666101 PUBLICATION DATE: 02/05/2004
Name: JOHNS 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
DESIGNATION: 866 6101 TIDAL 7
MONUMENTATION: Tidal Station disk VM#: 4254
AGENCY: National Ocean Survey (NOS) PID#: CK2636
SETTING CLASSIFICATION: Concrete monument
The bench mark is a disk set flush in a concrete monument east of north corner
of concrete patio slab, 28.16 m (92.4 ft) SSW of bench mark NO 6 1974, 17.77 m
(58.3 ft) ENE of east corner of Doss house, 15 m (49 ft) SSE of East corner of
concrete pump house, and 0.58 m (1.9 ft) east of north corner of concrete patio
pad.
BENCH MARK STAMPING: 6101 F 1977
DESIGNATION: 866 6101 F TIDAL
MONUMENTATION: Tidal Station disk VM#: 4255
AGENCY: National Ocean Survey (NOS) PID#: CK2637
SETTING CLASSIFICATION: Copper-clad steel rod
The bench mark is a disk located on north side of drive leading to Doss house,
49.38 m (162.0 ft) north of bench mark NO 6 1974, 20.88 m (68.5 ft) ENE of 1.28
m (4.2 ft) oak tree, 11.28 m (37.0 ft) WNW of centerline of dirt drive, and 7.19
m (23.6 ft) west of westernmost cedar flanking drive. The bench mark is set at
ground level, crimped to the top of a copper-clad steel rod driven 10.4 m (34
ft) 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
Station ID: 8666101 PUBLICATION DATE: 02/05/2004
Name: JOHNS 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
DESIGNATION: 866 6101 G TIDAL
MONUMENTATION: Tidal Station disk VM#: 4256
AGENCY: National Ocean Survey (NOS) PID#: CK2632
SETTING CLASSIFICATION: Copper-clad steel rod
The bench mark is a disk located south of drive leading to Doss House, 87 m (285
ft) NNE of bench mark 6101 F 1977, 7 m (23 ft) ESE of second power pole north of
house, 5 m (15 ft) from fourth crepe myrtle tree on east side of road. The
bench mark is set at ground level, crimped to the top of a copper-clad steel rod
driven 9.8 m (32 ft) to refusal, encased in 4-inch PVC pipe and concrete
kickblock.
BENCH MARK STAMPING: 6101 H 1977
DESIGNATION: 866 6101 H
MONUMENTATION: Tidal Station disk VM#: 4257
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Copper-clad steel rod
The bench mark is a disk located just north of drive leading to Doss House, 84 m
(276 ft) north of bench mark 6101 G 1977, 38.25 m (125.5 ft) SSW of third power
pole from house, and 6.40 m (21.0 ft) WNW of centerline of road. The bench mark
is set at ground level crimped to the top of a copper clad steel rod, driven 8.5
m (28 ft) 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
Station ID: 8666101 PUBLICATION DATE: 02/05/2004
Name: JOHNS 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 JOHNS ISLAND, CHURCH CREEK based on:
LENGTH OF SERIES: 1 YEAR
TIME PERIOD: March 1977 - February 1978
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 (06/01/1977) = 2.741
MEAN HIGHER HIGH WATER (MHHW) = 2.260
MEAN HIGH WATER (MHW) = 2.153
MEAN SEA LEVEL (MSL) = 1.332
NORTH AMERICAN VERTICAL DATUM-1988 (NAVD) = 1.325
MEAN TIDE LEVEL (MTL) = 1.109
MEAN LOW WATER (MLW) = 0.066
MEAN LOWER LOW WATER (MLLW) = 0.000
LOWEST OBSERVED WATER LEVEL (01/09/1978) = -0.914
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 1 1934 4.170 2.017
NO 2 1934 4.895 2.742
NO 4 1954 4.799 2.646
NO 6 1974 5.837 3.684
NO 7 1974 5.834 3.681
6101 F 1977 5.568 3.415
6101 G 1977 5.252 3.099
6101 H 1977 5.116 2.963
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8666101 PUBLICATION DATE: 02/05/2004
Name: JOHNS 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.