U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 05/09/2001
Station ID: 8444162 SUPERCEDED DATE: 04/21/2003
Name: BOSTON LIGHT, BOSTON HARBOR
MASSACHUSETTS
NOAA Chart: 13270 Latitude: 42° 19.7' N
USGS Quad: HULL Longitude: 70° 53.5' W
To reach the tidal bench marks from Hull, MA, go 2 km (1 nm) north of Hull, MA,
to Little Brewster Island which is 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, and the Boston Light gauge 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
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) PID:
SETTING CLASSIFICATION: Rock outcrop
The primary bench mark is a disk set flush 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) PID:
SETTING CLASSIFICATION: See descriptive text
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, 1.64 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 2 of 5
PUBLICATION DATE: 05/09/2001
Station ID: 8444162 SUPERCEDED DATE: 04/21/2003
Name: BOSTON LIGHT, BOSTON HARBOR
MASSACHUSETTS
NOAA Chart: 13270 Latitude: 42° 19.7' N
USGS Quad: HULL Longitude: 70° 53.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 10 1926
DESIGNATION: 844 4162 NO 10
MONUMENTATION: Bench Mark disk VM#: 16258
AGENCY: US Coast and Geodetic Survey (USC&GS) PID:
SETTING CLASSIFICATION: Rock outcrop
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 NO 9
MONUMENTATION: Bench Mark disk VM#: 16259
AGENCY: US Coast and Geodetic Survey (USC&GS) PID:
SETTING CLASSIFICATION: Rock outcrop
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 3 of 5
PUBLICATION DATE: 05/09/2001
Station ID: 8444162 SUPERCEDED DATE: 04/21/2003
Name: BOSTON LIGHT, BOSTON HARBOR
MASSACHUSETTS
NOAA Chart: 13270 Latitude: 42° 19.7' N
USGS Quad: HULL Longitude: 70° 53.5' W
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) PID:
SETTING CLASSIFICATION: Rock outcrop
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, 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 4 of 5
PUBLICATION DATE: 05/09/2001
Station ID: 8444162 SUPERCEDED DATE: 04/21/2003
Name: BOSTON LIGHT, BOSTON HARBOR
MASSACHUSETTS
NOAA Chart: 13270 Latitude: 42° 19.7' N
USGS Quad: HULL Longitude: 70° 53.5' W
T I D A L D A T U M S
Tidal datums at BOSTON LIGHT, BOSTON HARBOR based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: September 2000 - December 2000
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8443970 BOSTON, BOSTON HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.998
MEAN HIGH WATER MHW = 2.866
MEAN SEA LEVEL MSL = 1.495
MEAN TIDE LEVEL MTL = 1.480
MEAN LOW WATER MLW = 0.094
MEAN LOWER LOW WATER MLLW = 0.000
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
844 4162 NO 8 7.773 4.907
USE 1885 7.632 4.766
10 1926 4.843 1.977
9 1926 7.037 4.171
LITTLE BREWSTER 1981 8.393 5.527
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 05/09/2001
Station ID: 8444162 SUPERCEDED DATE: 04/21/2003
Name: BOSTON LIGHT, BOSTON HARBOR
MASSACHUSETTS
NOAA Chart: 13270 Latitude: 42° 19.7' N
USGS Quad: HULL Longitude: 70° 53.5' W
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 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.