U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8451351 PUBLICATION DATE: 05/20/2004
Name: SACHUEST
RI
NOAA Chart: 13221 Latitude: 41° 29.2' N ( 41.48670)
USGS Quad: SAKONNET POINT Longitude: 71° 14.3' W ( -71.23830)
To reach the tidal bench marks from Newport, Rhode Island, take State Route 138A
east which turns into Memorial Boulevard, then Purgatory Road to Sachuest, a
wildlife refuge. Take the first left (road blocked by a cable) to a dirt road
that will lead to the Flint Point which is located at the NE corner of Sachuest
Point. The bench marks are located in the rocks along the shoreline at Flint
Point. The tide gage was mounted onshore with the orifice and tubing extending
offshore. The tide staff was mounted on the rocks east of the tide gage.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1351 A 1977
DESIGNATION: 845 1351 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 2143
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 29.2' N ( 41.48670) LONGITUDE: 71° 14.3' W ( -71.23830)
The primary bench mark is a disk set flush in concrete on a rock outcrop at
Flint Point in Sachuest Wildlife Refuge, 30 m (100 ft) west of the east
shoreline, 7 m (24 ft) south of the north shoreline, and 4 m (14 ft) north from
the bottom of the incline that leads to the dirt road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8451351 PUBLICATION DATE: 05/20/2004
Name: SACHUEST
RI
NOAA Chart: 13221 Latitude: 41° 29.2' N ( 41.48670)
USGS Quad: SAKONNET POINT Longitude: 71° 14.3' W ( -71.23830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1351 B 1977
DESIGNATION: 845 1351 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 2144
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 29.2' N ( 41.48670) LONGITUDE: 71° 14.3' W ( -71.23830)
The bench mark is a disk set flush in concrete on a rock outcrop at Flint Point
in Sachuest Wildlife Refuge, 61 m (200 ft) north of bench mark 1351 C 1977, 30 m
(100 ft) south of the north shoreline, 10 m (33 ft) NE of the bottom of the
incline that leads to the dirt road, and 5 m (17 ft) west of the east shoreline.
BENCH MARK STAMPING: 1351 C 1977
DESIGNATION: 845 1351 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 2145
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 29.2' N ( 41.48670) LONGITUDE: 71° 14.3' W ( -71.23830)
The bench mark is a disk set flush in concrete on a rock outcrop at Flint Point
in Sachuest Wildlife Refuge, 61 m (200 ft) south of bench mark 1351 B 1977, 30 m
(100 ft) north of bench mark 1351 E 1977, 18 m (60 ft) south of bench mark 1351
D 1977, 16 m (52 ft) east of the centerline of the dirt road, and 5 m (50 ft)
west of the east shoreline.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8451351 PUBLICATION DATE: 05/20/2004
Name: SACHUEST
RI
NOAA Chart: 13221 Latitude: 41° 29.2' N ( 41.48670)
USGS Quad: SAKONNET POINT Longitude: 71° 14.3' W ( -71.23830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1351 D 1977
DESIGNATION: 845 1351 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 2146
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 29.2' N ( 41.48670) LONGITUDE: 71° 14.3' W ( -71.23830)
The bench mark is a disk set flush on concrete in a rock outcrop at Flint Point
in Sachuest Wildlife Refuge, 46 m (150 ft) west of the east shoreline, 18 m (60
ft) north of bench mark 1351 C 1977, and 5 m (15 ft) east from the bottom of the
incline leading to the dirt road.
BENCH MARK STAMPING: 1351 E 1977
DESIGNATION: 845 1351 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 2147
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 29.2' N ( 41.48670) LONGITUDE: 71° 14.3' W ( -71.23830)
The bench mark is a disk set flush in concrete on a rock outcrop at Flint Point
at Sachuest Wildlife Refuge, 46 m (150 ft) north of a large outcrop of white
marble like rocks, 30 m (100 ft) south of bench mark 1351 C 1977, 15 m (50 ft)
west of the east shoreline, and 14 m (46 ft) SE of the centerline of the dirt
road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8451351 PUBLICATION DATE: 05/20/2004
Name: SACHUEST
RI
NOAA Chart: 13221 Latitude: 41° 29.2' N ( 41.48670)
USGS Quad: SAKONNET POINT Longitude: 71° 14.3' W ( -71.23830)
T I D A L D A T U M S
Tidal datums at SACHUEST based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: August 1977 - September 1977
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8452660 NEWPORT, NARRAGANSETT BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 1.063
MEAN HIGH WATER MHW = 0.992
MEAN TIDE LEVEL MTL = 0.516
MEAN SEA LEVEL MSL = 0.474
MEAN LOW WATER MLW = 0.040
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1351 A 1977 2.252 1.260
1351 B 1977 2.113 1.121
1351 C 1977 3.925 2.933
1351 D 1977 2.671 1.679
1351 E 1977 3.808 2.816
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8451351 PUBLICATION DATE: 05/20/2004
Name: SACHUEST
RI
NOAA Chart: 13221 Latitude: 41° 29.2' N ( 41.48670)
USGS Quad: SAKONNET POINT Longitude: 71° 14.3' W ( -71.23830)
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.