U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8461925 PUBLICATION DATE: 04/21/2003
Name: NIANTIC, NIANTIC RIVER
CT
NOAA Chart: 13211 Latitude: 41° 19.5' N ( 41.32500)
USGS Quad: NIANTIC Longitude: 72° 11.2' W ( -72.18670)
To reach the tidal bench marks from the intersection of I-95 and State Route
161, proceed south on Route 161 for 5.0 km (3.1 mi) to Route 156 (Main Street),
then proceed east on Main Street for 0.3 km (0.2 mi) to Smith Avenue. Continue
north on Smith Avenue for 0.08 km (0.05 mi) to Grand Street then proceed east on
Grand Street for 0.2 km (0.1 mi) to Harbor Hill Marina. The bench marks are
located in the vicinity of the marina, and at the intersections of Grand Street,
Smith Avenue, Route 161, and Main Street. The tide gage and staff were attached
to pilings along the bulkhead at the north end of the marina.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1925 A 1993
DESIGNATION: 846 1925 A
MONUMENTATION: Tidal Station disk VM#: 12448
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete platform OPUS PID:
LATITUDE: 41° 19.5' N ( 41.32500) LONGITUDE: 72° 11.2' W ( -72.18670)
The primary bench mark is a disk set in the SW corner of the concrete marine
hoist platform at the Port Niantic Marina (17 Smith Avenue), 30 m (100 ft) NNE
of a large tree adjacent to the port office, 17.10 m (56.1 ft) SE of the NE
corner of the large boat storage building, 1.22 m (4.0 ft) NE of the SW corner
of the platform, and level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8461925 PUBLICATION DATE: 04/21/2003
Name: NIANTIC, NIANTIC RIVER
CT
NOAA Chart: 13211 Latitude: 41° 19.5' N ( 41.32500)
USGS Quad: NIANTIC Longitude: 72° 11.2' W ( -72.18670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1925 B 1993
DESIGNATION: 846 1925 B
MONUMENTATION: Tidal Station disk VM#: 12449
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete platform OPUS PID:
LATITUDE: 41° 19.5' N ( 41.32500) LONGITUDE: 72° 11.2' W ( -72.18670)
The bench mark is a disk set in the SE corner of the old concrete marine hoist
platform of the Boats Inc. Marina, 39 m (128 ft) east of the NE corner of the
Marina office building, 31 m (102 ft) north of the Marina flagpole, 16.25 m
(53.3 ft) south of the corner of the wooden bulkhead bordering the boat launch
ramp, and level with the ground.
BENCH MARK STAMPING: 370X
DESIGNATION: 846 1925 370X
MONUMENTATION: Bench Mark disk VM#: 12450
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 41° 19.5' N ( 41.32500) LONGITUDE: 72° 11.2' W ( -72.18670)
The bench mark is a disk set in a concrete monument along the south side of Main
Street south of the intersection of Route 161 and Main Street, 5.82 m (19.1 ft)
south of the centerline of Main Street, 3.63 m (11.9 ft) east of the extended
centerline of Route 161, 1.22 m (4.0 ft) NW of SNET utility pole 188, and 0.09 m
(0.3 ft) below the road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8461925 PUBLICATION DATE: 04/21/2003
Name: NIANTIC, NIANTIC RIVER
CT
NOAA Chart: 13211 Latitude: 41° 19.5' N ( 41.32500)
USGS Quad: NIANTIC Longitude: 72° 11.2' W ( -72.18670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4611
DESIGNATION: 846 1925 4611
MONUMENTATION: Survey disk VM#: 12452
AGENCY: Connecticut Geodetic Survey (CTGS) IDB PID#: LX5512
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 41° 19.5' N ( 41.32500) LONGITUDE: 72° 11.2' W ( -72.18670)
The bench mark is a disk set in top of a concrete monument at the SW corner of
the intersection of Smith Avenue and Main Street, 19.96 m (65.5 ft) NW of SNET
utility pole 177, 9.24 m (30.3 ft) west of the centerline of Smith Avenue, 5.43
m (17.8 ft) north of the centerline Main Street, and level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8461925 PUBLICATION DATE: 04/21/2003
Name: NIANTIC, NIANTIC RIVER
CT
NOAA Chart: 13211 Latitude: 41° 19.5' N ( 41.32500)
USGS Quad: NIANTIC Longitude: 72° 11.2' W ( -72.18670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LEWIS 2 1946
DESIGNATION: LEWIS 2
MONUMENTATION: Triangulation Station disk VM#: 12453
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX5485
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 41° 19.5' N ( 41.32500) LONGITUDE: 72° 11.2' W ( -72.18670)
The bench mark is a disk set in a concrete monument on top of a dirt bluff on
the south side of Grand Street, 25 m (82 ft) west of the mean high water line,
20.24 m (66.4 ft) north of a utility pole, 19 m (62 ft) south of the Grand
Street centerline, and 0.09 m (0.3 ft) above ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8461925 PUBLICATION DATE: 04/21/2003
Name: NIANTIC, NIANTIC RIVER
CT
NOAA Chart: 13211 Latitude: 41° 19.5' N ( 41.32500)
USGS Quad: NIANTIC Longitude: 72° 11.2' W ( -72.18670)
T I D A L D A T U M S
Tidal datums at NIANTIC, NIANTIC RIVER based on:
LENGTH OF SERIES: 2 Months
TIME PERIOD: July 1993 - August 1993
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8461490 NEW LONDON, THAMES RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.918
MEAN HIGH WATER MHW = 0.832
MEAN SEA LEVEL MSL = 0.446
MEAN TIDE LEVEL MTL = 0.440
MEAN LOW WATER MLW = 0.048
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1925 A 1993 1.517 0.685
1925 B 1993 2.490 1.658
370X 5.489 4.657
4611 3.931 3.099
LEWIS 2 1946 4.690 3.858
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8461925 PUBLICATION DATE: 04/21/2003
Name: NIANTIC, NIANTIC RIVER
CT
NOAA Chart: 13211 Latitude: 41° 19.5' N ( 41.32500)
USGS Quad: NIANTIC Longitude: 72° 11.2' W ( -72.18670)
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.