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National Ocean Service
Datums Page Page 1 of 5
Station ID: 8675622 PUBLICATION DATE: 05/12/2004
Name: OLD TOWER, SAPELO ISLAND, DOBOY SOUND
GA
NOAA Chart: 15110 Latitude: 31° 23.4' N ( 31.39000)
USGS Quad: DOBOY SOUND Longitude: 81° 17.3' W ( -81.28830)
To reach the tidal bench marks proceed by boat to the southern end of Sapelo
Island, Georgia at the entrance to Doboy Sound and adjacent to the abandoned
lighthouse. The bench marks are located along sandy roadway running parallel to
the oyster beds adjacent to the abandoned lighthouse at Doboy Sound. The tide
gage and staff were located on a platform built on a piling 91 m (300 ft)
offshore of the south end of Sapelo Island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5622 A 1977
DESIGNATION: 867 5622 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 4889
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID:
LATITUDE: 31° 23.4' N ( 31.39000) LONGITUDE: 81° 17.3' W ( -81.28830)
The primary bench mark is a disk located at the south end of Sapelo Island, near
the abandoned lighthouse on the west side of the sand road in the marshy area,
31.70 m (104.0 ft) SE of bench mark 5622 B 1977. The bench mark is crimped to
the top of an unspecified deep rod driven an unspecified depth 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: 8675622 PUBLICATION DATE: 05/12/2004
Name: OLD TOWER, SAPELO ISLAND, DOBOY SOUND
GA
NOAA Chart: 15110 Latitude: 31° 23.4' N ( 31.39000)
USGS Quad: DOBOY SOUND Longitude: 81° 17.3' W ( -81.28830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5622 B 1977
DESIGNATION: 867 5622 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 4890
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID:
LATITUDE: 31° 23.4' N ( 31.39000) LONGITUDE: 81° 17.3' W ( -81.28830)
The bench mark is a disk located at the south end of Sapelo Island, near the
abandoned lighthouse on the west side of road in marsh, 30.36 m (99.6 ft) SE of
bench mark 5622 C 1977. The bench mark is crimped to the top of an unspecified
deep rod driven an unspecified depth and encased in a 4-inch PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 5622 C 1977
DESIGNATION: 867 5622 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 4891
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID:
LATITUDE: 31° 23.4' N ( 31.39000) LONGITUDE: 81° 17.3' W ( -81.28830)
The bench mark is a disk located at the south end of Sapelo Island, near the
abandoned lighthouse, 37.49 m (123.0 ft) SE of bench mark 5622 D and 14.08 m
(46.2 ft) east of the sand road. The bench mark is crimped to the top of an
unspecified deep rod driven an unspecified depth 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 3 of 5
Station ID: 8675622 PUBLICATION DATE: 05/12/2004
Name: OLD TOWER, SAPELO ISLAND, DOBOY SOUND
GA
NOAA Chart: 15110 Latitude: 31° 23.4' N ( 31.39000)
USGS Quad: DOBOY SOUND Longitude: 81° 17.3' W ( -81.28830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5622 D 1977
DESIGNATION: 867 5622 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 4892
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID#: BBCD03
LATITUDE: 31° 23.4' N ( 31.39000) LONGITUDE: 81° 17.3' W ( -81.28830)
The bench mark is a disk located at the south end of Sapelo Island near the
abandoned lighthouse, 42.67 m (140.0 ft) NNE of bench mark 5622 E and 3.57 m
(11.7 ft) north of a sand road. The bench mark is crimped to the top of an
unspecified deep rod driven an unspecified depth and encased in a 4-inch PVC
pipe and concrete kickblock.
BENCH MARK STAMPING: 5622 E 1977
DESIGNATION: 867 5622 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 4893
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Unspecified deep rod OPUS PID:
LATITUDE: 31° 23.4' N ( 31.39000) LONGITUDE: 81° 17.3' W ( -81.28830)
The bench mark is a disk located at the south end of Sapelo Island, near the
abandoned lighthouse, along west side of sand road 8.35 m (27.4 ft) SE of
witness post and 5.18 m (17.0 ft) west of centerline of the road. The bench
mark is crimped to the top of an unspecified deep rod driven an unspecified
depth 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 4 of 5
Station ID: 8675622 PUBLICATION DATE: 05/12/2004
Name: OLD TOWER, SAPELO ISLAND, DOBOY SOUND
GA
NOAA Chart: 15110 Latitude: 31° 23.4' N ( 31.39000)
USGS Quad: DOBOY SOUND Longitude: 81° 17.3' W ( -81.28830)
T I D A L D A T U M S
Tidal datums at OLD TOWER, SAPELO ISLAND, DOBOY SOUND based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: July 1977 - December 1977
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8720030 FERNANDINA BEACH, AMELIA RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.264
MEAN HIGH WATER MHW = 2.143
MEAN SEA LEVEL MSL = 1.118
MEAN TIDE LEVEL MTL = 1.104
MEAN LOW WATER MLW = 0.064
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
5622 A 1977 2.459 0.316
5622 B 1977 2.390 0.247
5622 C 1977 3.410 1.267
5622 D 1977 3.503 1.360
5622 E 1977 3.126 0.983
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8675622 PUBLICATION DATE: 05/12/2004
Name: OLD TOWER, SAPELO ISLAND, DOBOY SOUND
GA
NOAA Chart: 15110 Latitude: 31° 23.4' N ( 31.39000)
USGS Quad: DOBOY SOUND Longitude: 81° 17.3' W ( -81.28830)
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.