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Datums Page Page 1 of 6
Station ID: 8466797 PUBLICATION DATE: 04/21/2003
Name: I-95 BRIDGE, HOUSATONIC RIVER
CT
NOAA Chart: 12370 Latitude: 41° 12.2' N ( 41.20330)
USGS Quad: MILFORFD Longitude: 73° 6.7' W ( -73.11170)
To reach the tidal bench marks from the west end of the U.S. Highway 1 bridge
over the Housatonic River in Stratford, proceed 0.5 km (0.3 mi) north through
the dock shopping complex to the Marina at the Dock. The bench marks are
located in the vicinity of the Marina, the west end of the railroad bridge, and
the shopping center. The tide gage and staff were located just south of the
boat launch at the Marina.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6797 B 1993
DESIGNATION: 846 6797 B
MONUMENTATION: Tidal Station disk VM#: 12462
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete head wall OPUS PID:
LATITUDE: 41° 12.2' N ( 41.20330) LONGITUDE: 73° 6.7' W ( -73.11170)
The primary bench mark is a disk set in the north end of a concrete headwall
near the east end of the marina boat storage area, 37 m (121 ft) NE of
fire-fighting pipe on an I-95 bridge pier, 20 m (66 ft) north of the bridge pier
with high voltage wires attached to it, and 13 m (42 ft) SSW of and downhill of
the SE corner of high voltage tower No. 862 along the railroad tracks.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8466797 PUBLICATION DATE: 04/21/2003
Name: I-95 BRIDGE, HOUSATONIC RIVER
CT
NOAA Chart: 12370 Latitude: 41° 12.2' N ( 41.20330)
USGS Quad: MILFORFD Longitude: 73° 6.7' W ( -73.11170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6797 A 1993
DESIGNATION: 846 6797 A
MONUMENTATION: Tidal Station disk VM#: 12461
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete retaining wall OPUS PID:
LATITUDE: 41° 12.2' N ( 41.20330) LONGITUDE: 73° 6.7' W ( -73.11170)
The bench mark is a disk set in the NE end of a concrete retaining wall at the
marina, 27.43 m (90.0 ft) NE of the NE corner of the marina office building,
11.83 m (38.8 ft) NNW of the inner NW corner of the boat launch, 2.04 m (6.7 ft)
SSE of a fire hydrant, and at ground level.
BENCH MARK STAMPING: 6797 C 1993
DESIGNATION: 846 6797 C
MONUMENTATION: Tidal Station disk VM#: 12463
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 12.2' N ( 41.20330) LONGITUDE: 73° 6.7' W ( -73.11170)
The bench mark is a disk set in a rock outcrop on the back side of The Dock
shopping center, 39.72 m (130.3 ft) NE of power pole number 5970, 26 m (85 ft)
SE and downhill of the SE corner of the I-95 bridge, 21.06 m (69.1 ft) SW of the
center of a fire hydrant, and 1 m (3 ft) above the pavement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8466797 PUBLICATION DATE: 04/21/2003
Name: I-95 BRIDGE, HOUSATONIC RIVER
CT
NOAA Chart: 12370 Latitude: 41° 12.2' N ( 41.20330)
USGS Quad: MILFORFD Longitude: 73° 6.7' W ( -73.11170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: A 34 1965
DESIGNATION: A 34
MONUMENTATION: Bench Mark disk VM#: 12464
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: LX0883
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 41° 12.0' N ( 41.20000) LONGITUDE: 73° 6.9' W ( -73.11500)
The bench mark is a disk set in top of the west end of a rock outcrop, 0.24 km
(0.15 mi) west of the west end of the U.S. Highway 1 bridge over the Housatonic
River, in the "Y" junction formed by Ferry Boulevard and U.S. Highway 1, 23.20 m
(76.1 ft) NW of the centerline of a traffic signal pole, 19.05 m (62.5 ft) NW of
the NW curb of the eastbound lane of Ferry Boulevard, 7 m (23 ft) east of the
east curb of a connectiing drive between the two highway lanes, and 2 m (6 ft)
above the level of the highway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8466797 PUBLICATION DATE: 04/21/2003
Name: I-95 BRIDGE, HOUSATONIC RIVER
CT
NOAA Chart: 12370 Latitude: 41° 12.2' N ( 41.20330)
USGS Quad: MILFORFD Longitude: 73° 6.7' W ( -73.11170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: Z 2
ALIAS: NO STAMPING 1
MONUMENTATION: Bolt VM#: 12465
AGENCY: Unknown IDB PID#: LX0885
SETTING CLASSIFICATION: Stone bridge abutment OPUS PID:
LATITUDE: 41° 12.3' N ( 41.20500) LONGITUDE: 73° 6.7' W ( -73.11170)
The bench mark is a bolt set on top of the south edge of the top stone at the
south end of the west abutment of the AMTRAK railroad bridge over the Housatonic
River, 3.54 m (11.6 ft) south of the south rail, 1.13 m (3.7 ft) east of the SW
corner of the abutment, and 0.3 m (1 ft) below the level of the track.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8466797 PUBLICATION DATE: 04/21/2003
Name: I-95 BRIDGE, HOUSATONIC RIVER
CT
NOAA Chart: 12370 Latitude: 41° 12.2' N ( 41.20330)
USGS Quad: MILFORFD Longitude: 73° 6.7' W ( -73.11170)
T I D A L D A T U M S
Tidal datums at I-95 BRIDGE, HOUSATONIC RIVER based on:
LENGTH OF SERIES: 3 Months
TIME PERIOD: June 1993 - August 1993
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8467150 BRIDGEPORT, BRIDGEPORT HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.182
MEAN HIGH WATER MHW = 2.080
North American Vertical Datum NAVD88 = 1.121
MEAN TIDE LEVEL MTL = 1.077
MEAN SEA LEVEL MSL = 1.067
MEAN LOW WATER MLW = 0.074
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6797 B 1993 4.145 2.065
6797 A 1993 3.997 1.917
6797 C 1993 5.577 3.497
A 34 1965 8.261 6.181
Z 2 10.040 7.960
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8466797 PUBLICATION DATE: 04/21/2003
Name: I-95 BRIDGE, HOUSATONIC RIVER
CT
NOAA Chart: 12370 Latitude: 41° 12.2' N ( 41.20330)
USGS Quad: MILFORFD Longitude: 73° 6.7' W ( -73.11170)
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.
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Station Location
Published bench mark
Unpublished bench mark