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National Ocean Service
Datums Page Page 1 of 6
Station ID: 8444162 PUBLICATION DATE: 10/14/2011
Name: BOSTON LIGHT, BOSTON HARBOR
MA
NOAA Chart: 13270 Latitude: 42° 19.7' N ( 42.32830)
USGS Quad: HULL Longitude: 70° 53.5' W ( -70.89170)
To reach the tidal bench marks from Hull, MA via boat, proceed north for 2 km (1
nm) to Little Brewster Island, near the mouth of Boston Harbor and what is known
as Nantasket Roads. The tidal bench marks are located on the island in the
vicinity of the tide station. The tide station is located at the end of the
boat landing area for the island.
T I D A L B E N C H M A R K S
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8444162 PUBLICATION DATE: 10/14/2011
Name: BOSTON LIGHT, BOSTON HARBOR
MA
NOAA Chart: 13270 Latitude: 42° 19.7' N ( 42.32830)
USGS Quad: HULL Longitude: 70° 53.5' W ( -70.89170)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
DESIGNATION: 844 4162 NO 8
ALIAS: NO STAMPING 1
MONUMENTATION: Tidal Station disk VM#: 16256
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 19.7' N ( 42.32830) LONGITUDE: 70° 53.5' W ( -70.89170)
The primary bench mark is a disk set vertically in a rock outcrop on the western
side of the island in front of and to the south of the westernmost house on
island, 2.74 m (9.0 ft) north of the main sidewalk which leads to the lighthouse
and dock, 1.37 m (4.5 ft) east of the centerline of a narrow sidewalk leading to
house.
BENCH MARK STAMPING: USE 1885
DESIGNATION: 844 4162 USE
MONUMENTATION: Chiseled Cross VM#: 16257
AGENCY: US Army Corps of Engineers (USE) IDB PID#:
SETTING CLASSIFICATION: See descriptive text OPUS PID:
LATITUDE: 42° 19.6' N ( 42.32670) LONGITUDE: 70° 53.5' W ( -70.89170)
The bench is a chisled x on top of a granite monument, 5.09 m (16.7 ft) west of
the SW corner of the light keepers house and near a flagpole, 5.09 m (16.7 ft)
WNW of the top step leading to the house, 1.65 m (5.4 ft) NE of a white
flagpole, and 0.09 m (0.3 ft) above ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8444162 PUBLICATION DATE: 10/14/2011
Name: BOSTON LIGHT, BOSTON HARBOR
MA
NOAA Chart: 13270 Latitude: 42° 19.7' N ( 42.32830)
USGS Quad: HULL Longitude: 70° 53.5' W ( -70.89170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 10 1926
DESIGNATION: 844 4162 TIDAL 10
MONUMENTATION: Tidal Station disk VM#: 16258
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 19.6' N ( 42.32670) LONGITUDE: 70° 53.6' W ( -70.89330)
The bench mark is a disk set in top of a rock ledge on the NW part of the
island, 17.83 m (58.5 ft) NW of the NW corner of the westernmost house on the
island, 14.63 m (48.0 ft) north of the centerline of the north concrete
adandoned pier.
BENCH MARK STAMPING: 9 1926
DESIGNATION: 844 4162 TIDAL 9
MONUMENTATION: Tidal Station disk VM#: 16259
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 19.7' N ( 42.32830) LONGITUDE: 70° 53.6' W ( -70.89330)
The bench mark is a disk set in top of a rock outcrop on the western part of the
island, 11.13 m (36.5 ft) south of a narrow sidewalk at the north end of the
rock outcrop, 7.32 m (24.0 ft) east of the SE corner of the westernmost house on
the island, 3.96 m (13.0 ft) NW of the centerline of the main sidewalk between
lighthouse and boathouse.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8444162 PUBLICATION DATE: 10/14/2011
Name: BOSTON LIGHT, BOSTON HARBOR
MA
NOAA Chart: 13270 Latitude: 42° 19.7' N ( 42.32830)
USGS Quad: HULL Longitude: 70° 53.5' W ( -70.89170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LITTLE BREWSTER 1981
DESIGNATION: 844 4162 LITTLE BREWSTER
MONUMENTATION: Tidal Station disk VM#: 16260
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 19.7' N ( 42.32830) LONGITUDE: 70° 53.4' W ( -70.89000)
The bench mark is a disk set flush in a rock outcrop on the hill near the
lighthouse, 25.51 m (83.7 ft) north of the north wall of the lighthouse, 17.31 m
(56.8 ft) WNW of the west corner of a utility garage, and 10.91 m (35.8 ft) NNE
of the north side of the most southern sidewalk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8444162 PUBLICATION DATE: 10/14/2011
Name: BOSTON LIGHT, BOSTON HARBOR
MA
NOAA Chart: 13270 Latitude: 42° 19.7' N ( 42.32830)
USGS Quad: HULL Longitude: 70° 53.5' W ( -70.89170)
T I D A L D A T U M S
Tidal datums at BOSTON LIGHT, BOSTON HARBOR based on:
LENGTH OF SERIES: 1 YEAR
TIME PERIOD: July 2001 - June 2002
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8443970 BOSTON, BOSTON HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (02/21/2004) = 3.595
MEAN HIGHER HIGH WATER MHHW = 2.992
MEAN HIGH WATER MHW = 2.858
MEAN SEA LEVEL MSL = 1.498
MEAN TIDE LEVEL MTL = 1.479
MEAN LOW WATER MLW = 0.100
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (02/12/2001) = -0.867
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
844 4162 NO 8 7.749 4.891
USE 1885 7.609 4.751
10 1926 4.819 1.961
9 1926 7.013 4.155
LITTLE BREWSTER 1981 8.368 5.510
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8444162 PUBLICATION DATE: 10/14/2011
Name: BOSTON LIGHT, BOSTON HARBOR
MA
NOAA Chart: 13270 Latitude: 42° 19.7' N ( 42.32830)
USGS Quad: HULL Longitude: 70° 53.5' W ( -70.89170)
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.