U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 6
Station ID: 8462764 PUBLICATION DATE: 05/07/2003
Name: LYME HWY. BR. CT. RIVER
CT
NOAA Chart: 12375 Latitude: 41° 19.3' N ( 41.32170)
USGS Quad: OLD LYME Longitude: 72° 21.0' W ( -72.35000)
To reach the tidal bench marks from the northernmost junction of U.S. Highway 1
and State Highway 154 in Old Saybrook, proceed NE on U.S. Highway 1 for 1.8 km
(1.1 mi), make a right turn onto Ferry Road just before the entrance to
Interstate Highway 95 north, proceed NE on Ferry Road for 1.6 km (1.0 mi)
Riverside Avenue, then north on Riverside Avenue for 0.24 km (0.15 mi) to the
entrance to the Seth Persson boat yard and Oak Leaf Marina. The bench marks are
along the waterfront to the south of the boat yard. The tide gage and staff
were at the north end of a T-shaped pier at the Oak Leaf Marina.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2764 D 1987
DESIGNATION: 846 2764 D
MONUMENTATION: Tidal Station disk VM#: 2235
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete footing OPUS PID:
LATITUDE: 41° 19.3' N ( 41.32170) LONGITUDE: 72° 21.0' W ( -72.35000)
The bench mark is a disk set in the SE concrete footing of a large high voltage
tower, 41 m (133 ft) east of the centerline of Ferry Road, 1.31 m (4.3 ft) NW of
the SE leg of the tower, 0.3 m (1 ft) south of the north edge of the concrete
footing, and 0.3 m (1 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8462764 PUBLICATION DATE: 05/07/2003
Name: LYME HWY. BR. CT. RIVER
CT
NOAA Chart: 12375 Latitude: 41° 19.3' N ( 41.32170)
USGS Quad: OLD LYME Longitude: 72° 21.0' W ( -72.35000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1 1938
DESIGNATION: TIDAL 1 STA 9
MONUMENTATION: Tidal Station disk VM#: 2232
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX0102
SETTING CLASSIFICATION: Large boulder OPUS PID:
LATITUDE: 41° 19.3' N ( 41.32170) LONGITUDE: 72° 21.0' W ( -72.35000)
The primary bench mark is a disk set in a large boulder NNE of the north yard of
Oak Leaf Marina, 112 m (367 ft) from the NW corner of the northernmost cottage
in the marina, 58 m (190 ft) NE of the centerline of a landing at the bottom of
a stairway leading from a gray house down to the river bank, 13 m (43 ft) east
of the bottom slope of a hill which runs parallel to the river bank, and 1 m (4
ft) above the beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8462764 PUBLICATION DATE: 05/07/2003
Name: LYME HWY. BR. CT. RIVER
CT
NOAA Chart: 12375 Latitude: 41° 19.3' N ( 41.32170)
USGS Quad: OLD LYME Longitude: 72° 21.0' W ( -72.35000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 6 1958
DESIGNATION: TIDAL 6 STA 9
MONUMENTATION: Tidal Station disk VM#: 2233
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX0101
SETTING CLASSIFICATION: Large bridge column base OPUS PID:
LATITUDE: 41° 19.3' N ( 41.32170) LONGITUDE: 72° 21.0' W ( -72.35000)
The bench mark is a disk set in the SE corner of the first footing of the Lyme
Highway bridge (Interstate Highway 95) on the west side of the river, 37.95 m
(124.5 ft) east of the centerline of Ferry Road, 0.24 m (0.8 ft) west of the
east edge of the base, 0.21 m (0.7 ft) north of the south upper edge of the
base, and 1.01 m (3.3 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8462764 PUBLICATION DATE: 05/07/2003
Name: LYME HWY. BR. CT. RIVER
CT
NOAA Chart: 12375 Latitude: 41° 19.3' N ( 41.32170)
USGS Quad: OLD LYME Longitude: 72° 21.0' W ( -72.35000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 7 1958
DESIGNATION: TIDAL 7 STA 9
MONUMENTATION: Tidal Station disk VM#: 2234
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX0100
SETTING CLASSIFICATION: Concrete retaining wall OPUS PID:
LATITUDE: 41° 18.8' N ( 41.31330) LONGITUDE: 72° 21.2' W ( -72.35330)
The bench mark is a disk set in the top of the north end of a concrete retaining
wall of Saybrook Marine Sales Company, 18 m (58 ft) NE of power pole #1759, 5 m
(16 ft) east of the centerline of Clark Street, 1.52 m (5.0 ft) south of the SW
corner of Saybrook Marine Sales building (2 Clark Street), and 0.3 m (1 ft)
above ground level and under a chain link fence on the retaining wall.
BENCH MARK STAMPING: 2764 E 1987
DESIGNATION: 846 2764 E
MONUMENTATION: Tidal Station disk VM#: 2236
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Retaining wall OPUS PID:
LATITUDE: 41° 19.3' N ( 41.32170) LONGITUDE: 72° 21.0' W ( -72.35000)
The bench mark is a disk set on top of a retaining wall on the east side of
Ferry Road south of the Lyme Highway bridge (Interstate Highway 95), 20 m (64
ft) NE of power pole #724, 7.16 m (23.5 ft) ESE of the centerline of Ferry Road,
4.42 m (14.5 ft) SSE of the north end of the retaining wall, 0.3 m (1 ft) west
of the edge of the wall, and level with the road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8462764 PUBLICATION DATE: 05/07/2003
Name: LYME HWY. BR. CT. RIVER
CT
NOAA Chart: 12375 Latitude: 41° 19.3' N ( 41.32170)
USGS Quad: OLD LYME Longitude: 72° 21.0' W ( -72.35000)
T I D A L D A T U M S
Tidal datums at LYME HWY. BR. CT. RIVER based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: June 1987 - August 1987
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 = 1.147
MEAN HIGH WATER MHW = 1.063
MEAN TIDE LEVEL MTL = 0.558
MEAN SEA LEVEL MSL = 0.557
MEAN LOW WATER MLW = 0.054
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2764 D 1987 9.738 8.675
1 1938 1.260 0.197
NO 6 1958 6.406 5.343
NO 7 1958 6.737 5.674
2764 E 1987 7.100 6.037
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8462764 PUBLICATION DATE: 05/07/2003
Name: LYME HWY. BR. CT. RIVER
CT
NOAA Chart: 12375 Latitude: 41° 19.3' N ( 41.32170)
USGS Quad: OLD LYME Longitude: 72° 21.0' W ( -72.35000)
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.