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Datums Page Page 1 of 5
Station ID: 8453999 PUBLICATION DATE: 07/12/2004
Name: BEAVERTAIL POINT
RI
NOAA Chart: 13223 Latitude: 41° 27.1' N ( 41.45170)
USGS Quad: NARRAGANSETT PIER Longitude: 71° 24.1' W ( -71.40170)
To reach the tidal bench marks from Newport, Rhode Island, travel west across
the Newport Bridge (toll) to Conanicut Island, go south on State Road 138 and
the road becomes Beavertail Road, follow Beavertail Road south to Beavertail
Point at the extreme southern end of the Island, at the Point take the last
turnoff on the right to a dirt road, 183 m (600 ft) north of the light at the
Point. On the dirt road take the first left fork and continue down to a small
parking area overlooking the tide station site. The bench marks are set in rock
at the base of a small cliff. The tide gage was mounted on top of the drop off
and the orifice and tubing extended offshore. The tide staff was bolted to
bedrock west of Bench Mark 3999 A 1977.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 3999 A 1977
DESIGNATION: 845 3999 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 2195
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 27.1' N ( 41.45170) LONGITUDE: 71° 24.1' W ( -71.40170)
The primary bench mark is a disk set flush in concrete in a large rock outcrop
NW of Beavertail Point, 9 m (30 ft) east of the shoreline, 5.64 m (18.5 ft) west
of a 3 m (9 ft) high rock face, 1 m (2 ft) north of a southern drop off and
bears NNW (340 magnetic) from Beavertail Light.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8453999 PUBLICATION DATE: 07/12/2004
Name: BEAVERTAIL POINT
RI
NOAA Chart: 13223 Latitude: 41° 27.1' N ( 41.45170)
USGS Quad: NARRAGANSETT PIER Longitude: 71° 24.1' W ( -71.40170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3999 B 1977
DESIGNATION: 845 3999 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 2196
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 27.1' N ( 41.45170) LONGITUDE: 71° 24.1' W ( -71.40170)
The bench mark is a disk set flush in concrete in a large rock outcrop NW of
Beavertail Point, 14 m (45 ft) south of a ravine leading to the beach, 12 m (41
ft) west of the vegetation line, 5 m (16 ft) east from a drop off to a small
gravel beach and bears NNW (344 magnetic) of Beavertail Light.
BENCH MARK STAMPING: 3999 C 1977
DESIGNATION: 845 3999 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 2197
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 27.1' N ( 41.45170) LONGITUDE: 71° 24.1' W ( -71.40170)
The bench mark is a disk set flush in concrete in a large rock outcrop NW of
Beavertail Point, 15 m (50 ft) west from a dirt foot path west of a vegetation
line, 2 m (6 ft) north of a drop off to the beach, 1 m (3 ft) south of a steep
drop off and bears NNW (329 magnetic) of Beavertail Light.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8453999 PUBLICATION DATE: 07/12/2004
Name: BEAVERTAIL POINT
RI
NOAA Chart: 13223 Latitude: 41° 27.1' N ( 41.45170)
USGS Quad: NARRAGANSETT PIER Longitude: 71° 24.1' W ( -71.40170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3999 D 1977
DESIGNATION: 845 3999 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 2198
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 27.1' N ( 41.45170) LONGITUDE: 71° 24.1' W ( -71.40170)
The bench mark is a disk set flush in concrete in a large rock outcrop NW of
Beavertail Point, 14 m (45 ft) east from the western shoreline, 11 m (36 ft)
west of the vegetation line, 5 m (15 ft) north of a steep drop off to the beach,
2 m (8 ft) south from a 1 m (2 ft) drop off, and bears NNW (341 magnetic) of
Beavertail Light.
BENCH MARK STAMPING: 3999 E 1977
DESIGNATION: 845 3999 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 2199
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 27.1' N ( 41.45170) LONGITUDE: 71° 24.1' W ( -71.40170)
The bench mark is a disk set flush in concrete in a large rock outcrop NW of
Beavertail Point, 10 m (32 ft) west of the drop off to the beach, 9 m (29 ft)
south of a rock ravine, 6 m (21 ft) west of a foot path at the edge of the
vegetation line, and bears NNW (343 magnetic) from Beavertail Light.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8453999 PUBLICATION DATE: 07/12/2004
Name: BEAVERTAIL POINT
RI
NOAA Chart: 13223 Latitude: 41° 27.1' N ( 41.45170)
USGS Quad: NARRAGANSETT PIER Longitude: 71° 24.1' W ( -71.40170)
T I D A L D A T U M S
Tidal datums at BEAVERTAIL POINT 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 = 1.155
MEAN HIGH WATER MHW = 1.075
MEAN TIDE LEVEL MTL = 0.566
MEAN LOW WATER MLW = 0.057
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
3999 A 1977 2.744 1.669
3999 B 1977 3.762 2.687
3999 C 1977 6.237 5.162
3999 D 1977 6.004 4.929
3999 E 1977 4.303 3.228
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8453999 PUBLICATION DATE: 07/12/2004
Name: BEAVERTAIL POINT
RI
NOAA Chart: 13223 Latitude: 41° 27.1' N ( 41.45170)
USGS Quad: NARRAGANSETT PIER Longitude: 71° 24.1' W ( -71.40170)
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.