U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8450768 PUBLICATION DATE: 05/20/2004
Name: SAKONNET
RI
NOAA Chart: 13221 Latitude: 41° 27.9' N ( 41.46500)
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W ( -71.19330)
To reach the tidal bench marks from the intersection of Rhode Island Highway 24
and State Road 77 in Tiverton, proceed south on State Road 77 for 16 km (10 mi)
to Sakonnet Point Road, then turn right and proceed west on 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
DESIGNATION: 845 0768 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 2118
AGENCY: US Coast & Geodetic Survey
(USC&GS) IDB PID#: LW0620
SETTING CLASSIFICATION: Mass of bedrock OPUS PID:
LATITUDE: 41° 27.8' N ( 41.46330) LONGITUDE: 71° 11.7' W ( -71.19500)
The primary bench mark is a disk set on the SW slope of a large mass of bedrock
which extends out into the Sakonnet River, located at the Sakonnet Yacht Club,
35 m (115 ft) north of the north side of the Sakonnet Yacht Club Building, 32 m
(104 ft) west of and across the road from power pole #430, 24.54 m (80.5 ft)
west of the centerline of Route 77, 15 m (49 ft) NW of the north end of a long
sea wall, 6 m (20 ft) NE of the SW end of a rock, 3 m (10 ft) east of the
shoreline, and set 0.91 m (3.0 ft) below level of the Highway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8450768 PUBLICATION DATE: 05/20/2004
Name: SAKONNET
RI
NOAA Chart: 13221 Latitude: 41° 27.9' N ( 41.46500)
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W ( -71.19330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 2 1957
DESIGNATION: 845 0768 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 2119
AGENCY: US Coast & Geodetic Survey
(USC&GS) IDB PID#: LW0622
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 41° 27.8' N ( 41.46330) LONGITUDE: 71° 11.7' W ( -71.19500)
The bench mark is a disk set flush in top of a 0.46 m (1.5 ft) wide concrete sea
wall at the Sakonnet Yacht Club, 101 m (330 ft) south of the south side of the
Sakonnet Yacht Club Building, 16.31 m (53.5 ft) SW of and across the road from
power pole #433, 7 m (23 ft) west of the centerline of Route 77, 6.25 m (20.5
ft) north of south end of the sea wall, and set 0.61 m (2.0 ft) above ground
level.
BENCH MARK STAMPING: NO 3 1957
DESIGNATION: 845 0768 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 2120
AGENCY: US Coast & Geodetic Survey
(USC&GS) IDB PID#: LW0624
SETTING CLASSIFICATION: Mass of bedrock OPUS PID:
LATITUDE: 41° 27.8' N ( 41.46330) LONGITUDE: 71° 11.4' W ( -71.19000)
The bench mark is a disk set on the top of the highest part of a large mass of
bedrock which is visible from the Yacht Club Building projecting 3 m (10 ft)
above ground level, in the vicinity of the Sakonnet Yacht Club, 0.2 km (0.1 mi)
east of the Sakonnet Yacht Club Building, 18.44 m (60.5 ft) south of power pole
#1679, 17 m (57 ft) north of the north side of a small building, and about 5 m
(15 ft) above the level of the highway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8450768 PUBLICATION DATE: 05/20/2004
Name: SAKONNET
RI
NOAA Chart: 13221 Latitude: 41° 27.9' N ( 41.46500)
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W ( -71.19330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0768 D 1977
DESIGNATION: 845 0768 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 2121
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 41° 27.9' N ( 41.46500) LONGITUDE: 71° 11.6' W ( -71.19330)
The bench mark is a disk set flush in top of a 0.46 m (1.5 ft) wide concrete sea
wall south of the Sakonnet Yacht Club, 43 m (140 ft) SE (230 magnetic) of bench
mark 0768 E 1977, and 36 m (117 ft) NNE (20 magnetic) of bench mark N0 2 1957.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8450768 PUBLICATION DATE: 05/20/2004
Name: SAKONNET
RI
NOAA Chart: 13221 Latitude: 41° 27.9' N ( 41.46500)
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W ( -71.19330)
T I D A L D A T U M S
Tidal datums at SAKONNET based on:
LENGTH OF SERIES: 7 MONTHS
TIME PERIOD: April 1992 - October 1992
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8452660 NEWPORT, NARRAGANSETT BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (09/21/1938) =
MEAN HIGHER HIGH WATER MHHW = 1.082
MEAN HIGH WATER MHW = 1.003
North American Vertical Datum NAVD88 = 0.595
MEAN TIDE LEVEL MTL = 0.519
MEAN SEA LEVEL MSL = 0.489
MEAN LOW WATER MLW = 0.036
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (02/03/1976) =
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 1 1957 2.422 1.419
NO 2 1957 2.632 1.629
NO 3 1957 5.456 4.453
0768 D 1977 2.757 1.754
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8450768 PUBLICATION DATE: 05/20/2004
Name: SAKONNET
RI
NOAA Chart: 13221 Latitude: 41° 27.9' N ( 41.46500)
USGS Quad: SAKONNET POINT Longitude: 71° 11.6' W ( -71.19330)
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.