U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 10/30/1985
Station ID: 8450768 SUPERCEDED DATE: 04/21/2003
Name: SAKONNET, SAKONNET RIVER
RHODE ISLAND
NOAA Chart: 13221 Latitude: 41° 27.9' N
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W
To reach the tidal bench marks from the intersection of Rhode Island Highway 24
and State Road 77 in Tiverton, proceed south 10 miles (16 km) on Route 77 to
Sakonnet Point Road, turn right (west) onto Sakonnet Point Road and travel to
the Sakonnet Yacht Club located on the west side of Sakonnet Point Road. The
bench marks are in the vicinity of the Yacht Club. The tide gage and staff were
located on the west end of the Yacht Club Pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1957
MONUMENTATION: Survey Disk VM#: 2118
AGENCY: PID#: LW0620
SETTING CLASSIFICATION: Rock
The bench mark is at the Sakonnet Yacht Club, 115 feet (35 m) north of the north
side of the Sakonnet Yacht Club Building, 104 feet (32 m) west of and across the
road from power pole #430, 80.5 feet (24.5 m) west of the centerline of Route
77, 49 feet (15 m) NW of the north end of a long seawall, set on the SW slope of
a large mass of bedrock which extends out into the Sakonnet River, 20 feet (6 m)
NE of the SW end of a rock, 10 feet (3 m) east of the shoreline, set 3 feet (0.9
m) below level of the Highway.
BENCH MARK STAMPING: NO 2 1957
MONUMENTATION: Survey Disk VM#: 2119
AGENCY: PID#: LW0622
SETTING CLASSIFICATION: Concrete Seawall
The bench mark is set flush in top of a 1.5 feet (0.5 m) wide concrete seawall
at the Sakonnet Yacht Club, 330 feet (101 m) south of the south side of the
Sakonnet Yacht Club Building, 53.5 feet (16.3 m) SW of and across the road from
power pole #433, 23 feet (7 m) west of the centerline of Route 77, 20.5 feet
(6.2 m) north of south end of the seawall, set 2 feet (0.6 m) above ground
level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 10/30/1985
Station ID: 8450768 SUPERCEDED DATE: 04/21/2003
Name: SAKONNET, SAKONNET RIVER
RHODE ISLAND
NOAA Chart: 13221 Latitude: 41° 27.9' N
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1957
MONUMENTATION: Survey Disk VM#: 2120
AGENCY: PID#: LW0624
SETTING CLASSIFICATION: Rock Outcrop
The bench mark is in the vicinity of the Sakonnet Yacht Club, 0.1 mile (0.2 km)
east of the Sakonnet Yacht Club Building, set on the top of the highest part of
a large mass of bedrock which is visible from the Yacht Club Building projecting
10 feet (3 m) above ground level, 60.5 feet (18.4 m) south of power pole #1679,
57 feet (17 m) north of the north side of a small building, and about 15 feet (5
m) above the level of the highway.
BENCH MARK STAMPING: 0768 D 1977
MONUMENTATION: Survey Disk VM#: 2121
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Seawall
The bench mark is set flush in top of a 1.5 foot (0.5 m) wide concrete seawall
south of the Sakonnet Yacht Club, 140 feet (43 m) SE (230 ) of Bench Mark 0768 E
1977, and 117 feet (36 m) NNE (20 ) of Bench Mark N0 2 1957.
BENCH MARK STAMPING: 0768 E 1977
MONUMENTATION: Survey Disk VM#: 2122
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Seawall
The bench mark is set flush in top of a 1.5 foot (0.5 m) wide concrete seawall
at the entrance to the Sakonnet Yacht Club Wharf in the SE corner of the Yacht
Club, 151 feet (46 m) north of Bench Mark N0 2 1957, 23 feet (7 m) SE (145 ) of
the SE corner of the Yacht Club.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 10/30/1985
Station ID: 8450768 SUPERCEDED DATE: 04/21/2003
Name: SAKONNET, SAKONNET RIVER
RHODE ISLAND
NOAA Chart: 13221 Latitude: 41° 27.9' N
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W
T I D A L D A T U M S
Tidal datums at SAKONNET, SAKONNET RIVER based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: AUGUST - OCTOBER 1977
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8452660 NEWPORT
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (11/11/1977) = 5.55
MEAN HIGHER HIGH WATER MHHW = 3.63
MEAN HIGH WATER MHW = 3.37
MEAN TIDE LEVEL MTL = 1.75
* NATIONAL GEODETIC VERTICAL DATUM NGVD29 = 1.42
MEAN LOW WATER MLW = 0.12
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (10/17/1977) = -1.02
* NGVD reference based on elevations published in Quad 410712, 1970, and NOS
leveling of 1977.
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1957 8.15 4.78
NO 2 1957 8.85 5.48
NO 3 1957 18.10 14.73
0768 D 1977 9.25 5.88
0768 E 1977 8.01 4.64
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 10/30/1985
Station ID: 8450768 SUPERCEDED DATE: 04/21/2003
Name: SAKONNET, SAKONNET RIVER
RHODE ISLAND
NOAA Chart: 13221 Latitude: 41° 27.9' N
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' 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.