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National Ocean Service
Datums Page Page 1 of 4
Station ID: 8452944 PUBLICATION DATE: 05/20/2020
Name: CONIMICUT LIGHT, NARRAGANSETT BAY
RI
NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667)
USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333)
To reach the Conimicut Light tidal station head north in boat towards
providence, RI, lighthouse is just south of the city in the Narragansett Bay.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
DESIGNATION: 845 2944 BOLT
ALIAS: BOLT
MONUMENTATION: Bolt VM#: 16300
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Steel bolt OPUS PID:
LATITUDE: 41° 43.0' N ( 41.71697) LONGITUDE: 71° 20.7' W ( -71.34508)
The primary bench mark is a steel bolt with a chiseled X in the top of it,
located on the south side of the lighthouse in the third handrail pole from the
catwalk, 4.22 m (13.8 ft) south of the south side of handrail, 1.22 m (4.0 ft)
SE of the side of the lighthouse, and 0.05 m (0.2 ft) NE of the bottom outer
steel bulkhead around the lighthouse.
BENCH MARK STAMPING:
DESIGNATION: 845 2944 SRM
MONUMENTATION: Chiseled Square VM#: 16017
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Metal pier I-beam OPUS PID:
LATITUDE: 41° 43.0' N ( 41.71708) LONGITUDE: 71° 20.7' W ( -71.34511)
The bench mark is a chiseled square at the NW corner of the catwalk to the
lighthouse, 7.65 m (25.1 ft) north of the north side of the lighthouse base,
1.80 m (5.9 ft) NW of the 4" protective well, and 1.45 m (4.8 ft) NNW of the SE
corner of the walkway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 8452944 PUBLICATION DATE: 05/20/2020
Name: CONIMICUT LIGHT, NARRAGANSETT BAY
RI
NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667)
USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2944 A 2004
DESIGNATION: 845 2944 A
MONUMENTATION: Tidal Station disk VM#: 17662
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Lighthouse foundation OPUS PID:
LATITUDE: 41° 43.0' N ( 41.71697) LONGITUDE: 71° 20.7' W ( -71.34511)
The bench mark is a disk set in the concrete walkway around the lighthouse near
the top of the stairs, 7.95 m (26.1 ft) south of the north end of the catwalk
leading to the lighthouse, 4.03 m (13.2 ft) NNE of the center of the door
leading into the lighthouse, and 0.98 m (3.2 ft) north of the lighthouse wall.
BENCH MARK STAMPING: 2944 B 2004
DESIGNATION: 845 2944 B
MONUMENTATION: Tidal Station disk VM#: 17663
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete walkway OPUS PID:
LATITUDE: 41° 43.0' N ( 41.71694) LONGITUDE: 71° 20.7' W ( -71.34508)
The bench mark is a disk set in the concrete walkway around the lighthouse, 1.80
m (5.9 ft) SSW of the center of the three solar panels mounted on the handrail,
0.79 m (2.6 ft) ESE of the lighthouse wall, and 0.50 m (1.6 ft) WNW of the outer
edge of the lighthouse base.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 8452944 PUBLICATION DATE: 05/20/2020
Name: CONIMICUT LIGHT, NARRAGANSETT BAY
RI
NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667)
USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333)
T I D A L D A T U M S
Tidal datums at CONIMICUT LIGHT, NARRAGANSETT BAY based on:
LENGTH OF SERIES: 15 YEARS
TIME PERIOD: 8/01-7/09,5/10-4/12,6/12-5/13,9/13-8/14,4/15-3/18
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8454000 PROVIDENCE, PROVIDENCE RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (10/29/2012) = 2.743
MEAN HIGHER HIGH WATER MHHW = 1.398
MEAN HIGH WATER MHW = 1.322
MEAN TIDE LEVEL MTL = 0.687
MEAN SEA LEVEL MSL = 0.642
MEAN LOW WATER MLW = 0.052
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (02/11/2001) = -0.851
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
845 2944 BOLT 4.882 3.560
845 2944 SRM 3.108 1.786
2944 A 2004 4.882 3.560
2944 B 2004 4.892 3.570
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 8452944 PUBLICATION DATE: 05/20/2020
Name: CONIMICUT LIGHT, NARRAGANSETT BAY
RI
NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667)
USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333)
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.