U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8440452 PUBLICATION DATE: 09/16/2003
Name: PLUM ISLAND, MERRIMACK RIVER ENTRANCE
MA
NOAA Chart: 13282 Latitude: 42° 49.0' N ( 42.81670)
USGS Quad: NEWBURYPORT EAST Longitude: 70° 49.2' W ( -70.82000)
To reach the tidal bench marks from the U.S. Coast Guard Station on Water Street
in Newburyport, proceed SW on Water Street for 4.8 km (3.0 mi) to Northern
Boulevard on Plum Island, then turn left and proceed north on Northern Boulevard
(Point Road) for 2.6 km (1.6 mi) to the abandoned Coast Guard Auxiliary Station
at Plum Island Point. The bench marks are near the large parking lot at the
point and near Newburyport Light. The tide station was on the NE abandoned Coast
Guard pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: TBM NO 1 1953
DESIGNATION: 844 0452 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 1456
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: ' °deg (0) LONGITUDE: ' °deg (0)
The primary bench mark is a disk set in the NW corner of the concrete foundation
for the wooden stairs at the south end of the U.S. Coast Guard Auxiliary
Station, 29.63 m (97.2 ft) east of power pole #18824, 24.23 m (79.5 ft) NNE of a
power pole in the SW area of the Auxiliary Station compound, 16.25 m (53.3 ft)
NE of the north corner of the easternmost of two red pump houses, 8.38 m (27.5
ft) SW of the east corner of the Auxiliary Station building, 0.55 m (1.8 ft) SE
of the west corner of the foundation, and 0.09 m (0.3 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8440452 PUBLICATION DATE: 09/16/2003
Name: PLUM ISLAND, MERRIMACK RIVER ENTRANCE
MA
NOAA Chart: 13282 Latitude: 42° 49.0' N ( 42.81670)
USGS Quad: NEWBURYPORT EAST Longitude: 70° 49.2' W ( -70.82000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: TBM NO 2 1953
DESIGNATION: 844 0452 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 1457
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation for Flagpole OPUS PID#: BBBJ41
LATITUDE: 42° 49.0' N ( 42.81670) LONGITUDE: 70° 49.2' W ( -70.82000)
The bench mark is a disk set in the concrete base of a former flag pole on the
grounds of the headquarters for Parker River National Wildlife Refuge, 25.39 m
(83.3 ft) SW of power pole #31, 24.48 m (80.3 ft) NW of a flag pole, 17.62 m
(57.8 ft) NE of the NE corner of the light keeper's house, 8.17 m (26.8 ft)
south of a 1.07 m (3.5 ft) diameter concrete well casing, 8 m (26 ft) NNE of the
northernmost of two bird house poles, and 0.21 m (0.7 ft) below ground level.
BENCH MARK STAMPING: 0452 A 1989
DESIGNATION: 844 0452 A
MONUMENTATION: Tidal Station disk VM#: 1458
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete loading dock OPUS PID:
LATITUDE: ' °deg (0) LONGITUDE: ' °deg (0)
The bench mark is a disk set in the south corner of the concrete loading dock of
the Division of Marine Fisheries Shellfish Purification Plant, 27.46 m (90.1 ft)
WSW of power pole #A579, 11.06 m (36.3 ft) SSW of the east corner of the loading
dock, 0.49 m (1.6 ft) north of the south corner of the loading dock, and 0.52 m
(1.7 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8440452 PUBLICATION DATE: 09/16/2003
Name: PLUM ISLAND, MERRIMACK RIVER ENTRANCE
MA
NOAA Chart: 13282 Latitude: 42° 49.0' N ( 42.81670)
USGS Quad: NEWBURYPORT EAST Longitude: 70° 49.2' W ( -70.82000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0452 B 1989
DESIGNATION: 844 0452 B
MONUMENTATION: Tidal Station disk VM#: 1459
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete slab OPUS PID:
LATITUDE: ' °deg (0) LONGITUDE: ' °deg (0)
The bench mark is a disk set in the west corner of a concrete slab NW of
Merrimack Fire Department Plum Island Station, 63 m (206 ft) NW of the NW corner
of the fire station, 17.53 m (57.5 ft) NNE of power pole #188-18, 9.97 m (32.7
ft) WSW of the NW corner of Plum Island Comfort Station, 5.64 m (18.5 ft) SSW of
the north edge of the slab, and 0.15 m (0.5 ft) above ground level.
BENCH MARK STAMPING: 0452 C 1989
DESIGNATION: 844 0452 C
MONUMENTATION: Tidal Station disk VM#: 1460
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: ' °deg (0) LONGITUDE: ' °deg (0)
The bench mark is a disk set in the south corner of the concrete foundation for
the Parker River National Wildlife Refuge headquarters radio tower, 34 m (111
ft) south of the headquarters' flag pole, 20.03 m (65.7 ft) NE of the north
corner of a cinderblock storage shed SW of the headquarters building, 1.37 m
(4.5 ft) SSE of the west corner of the building, and 0.21 m (0.7 ft) above
ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8440452 PUBLICATION DATE: 09/16/2003
Name: PLUM ISLAND, MERRIMACK RIVER ENTRANCE
MA
NOAA Chart: 13282 Latitude: 42° 49.0' N ( 42.81670)
USGS Quad: NEWBURYPORT EAST Longitude: 70° 49.2' W ( -70.82000)
T I D A L D A T U M S
Tidal datums at PLUM ISLAND, MERRIMACK RIVER ENTRANCE based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: June 1989 - September 1989
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8440466 NEWBURYPORT, MERRIMACK RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.654
MEAN HIGH WATER MHW = 2.529
MEAN TIDE LEVEL MTL = 1.310
MEAN SEA LEVEL MSL = 1.308
MEAN LOW WATER MLW = 0.091
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
TBM NO 1 1953 4.256 1.727
TBM NO 2 1953 4.183 1.654
0452 A 1989 3.844 1.315
0452 B 1989 3.432 0.903
0452 C 1989 4.843 2.314
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8440452 PUBLICATION DATE: 09/16/2003
Name: PLUM ISLAND, MERRIMACK RIVER ENTRANCE
MA
NOAA Chart: 13282 Latitude: 42° 49.0' N ( 42.81670)
USGS Quad: NEWBURYPORT EAST Longitude: 70° 49.2' W ( -70.82000)
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.