U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8453201 PUBLICATION DATE: 07/12/2004
Name: CASTLE HILL
RHODE ISLAND
NOAA Chart: 13223 Latitude: 41° 27.8' N
USGS Quad: NEWPORT Longitude: 71° 21.7' W
To reach the tidal bench marks from Thames Street on the waterfront in Newport,
Rhode Island, proceed south and follow the roads nearest the shoreline,
Wellington Avenue, Harrison Avenue, and Ridge Road to Castle Hill in Newport
Neck. The bench marks are set in the rocks at the base of the cliff between the
Castle Hill Inn and the Castle Hill Light, and behind the gravel beach near the
parking lot. The tide gage was set on top of the cliff behind the Castle Hill
Inn parking lot with the orifice and tubing extending offshore, and the tide
staff was bolted to bedrock at the shoreline behind the Castle Hill Inn parking
lot.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 3201 A 1977
DESIGNATION: 845 3201 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 2169
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Bedrock
The primary bench mark is a disk set flush in bedrock at the base of the cliff
behind the Castle Hill Inn parking lot, 31 m (103 ft) north (9 magnetic) of the
north edge of a gravel beach, 20 m (66 ft) NNW (352 magnetic) of bench mark
3201 B 1977, 2 m (5 ft) SW from the base of the cliff, and bears NE (38
magnetic) of Castle Hill Light.
BENCH MARK STAMPING: 3201 B 1977
DESIGNATION: 845 3201 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 2170
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Large rock
The bench mark is a disk set flush in a large rock at the base of a cliff, south
of the Castle Hill Inn parking lot, 20 m (66 ft) SSE (172 magnetic) of bench
mark 3201 A 1977, 19 m (62 ft) NE (6 magnetic) of bench mark 3201 C 1977, 12 m
(41 ft) NNE (22 magnetic) of the north edge of a gravel beach, 3 m (10 ft) from
the crevice in the northern face of the cliff and bears NE (40 magnetic) from
the Castle Hill Light.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8453201 PUBLICATION DATE: 07/12/2004
Name: CASTLE HILL
RHODE ISLAND
NOAA Chart: 13223 Latitude: 41° 27.8' N
USGS Quad: NEWPORT Longitude: 71° 21.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3201 C 1977
DESIGNATION: 845 3201 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 2171
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Rock
The bench mark is a disk set flush in a rock at the base of a cliff, between the
Castle Hill Light and the Castle Hill Inn parking lot, 23 m (74 ft) NE (36
magnetic) of bench mark 3201 D 1977, 19 m (62 ft) SW (242 magnetic) of bench
mark 3201 B 1977, bears NE (40 magnetic) from the flagpole at the Castle Hill
Light and is set on a rock outcropping in the east corner of a gravel beach.
BENCH MARK STAMPING: 3201 D 1977
DESIGNATION: 845 3201 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 2172
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Rock
The bench mark is a disk set flush in rock at the base of a cliff between the
Castle Hill Light and the Castle Hill Inn parking lot, 23 m (74 ft) SW (216
magnetic) of bench mark 3201 C 1977, 16.86 m (55.3 ft) ENE (70 magnetic) of
bench mark 3201 E 1977, 12 m (40 ft) SSE (156 magnetic) of the southernmost
edge of a gravel beach and is set at the vegetation line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8453201 PUBLICATION DATE: 07/12/2004
Name: CASTLE HILL
RHODE ISLAND
NOAA Chart: 13223 Latitude: 41° 27.8' N
USGS Quad: NEWPORT Longitude: 71° 21.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3201 E 1977
DESIGNATION: 845 3201 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 2173
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Rock
The bench mark is a disk set flush in rock at the base of a cliff between the
Castle Hill Light and Castle Hill Inn parking lot, 20 m (66 ft) SSW (210
magnetic) from the SW edge of a gravel beach, 16.86 m (55.3 ft) WSW (250 ) of
bench mark 3201 D 1977, bears NE (43 magnetic) from the flagpole at the Castle
Hill Light, and is set at the vegetation line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8453201 PUBLICATION DATE: 07/12/2004
Name: CASTLE HILL
RHODE ISLAND
NOAA Chart: 13223 Latitude: 41° 27.8' N
USGS Quad: NEWPORT Longitude: 71° 21.7' W
T I D A L D A T U M S
Tidal datums at CASTLE HILL based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: August 1977 - October 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) = 1.108
MEAN HIGH WATER (MHW) = 1.034
MEAN TIDE LEVEL (MTL) = 0.539
MEAN SEA LEVEL (MSL) = 0.497
MEAN LOW WATER (MLW) = 0.044
MEAN LOWER LOW WATER (MLLW) = 0.000
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
3201 A 1977 3.956 2.922
3201 B 1977 4.128 3.094
3201 C 1977 3.330 2.296
3201 D 1977 5.003 3.969
3201 E 1977 6.916 5.882
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8453201 PUBLICATION DATE: 07/12/2004
Name: CASTLE HILL
RHODE ISLAND
NOAA Chart: 13223 Latitude: 41° 27.8' N
USGS Quad: NEWPORT Longitude: 71° 21.7' 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.