U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 06/19/1991
Station ID: 8446009 SUPERCEDED DATE: 04/21/2003
Name: BRANT ROCK, GREEN HARBOR RIVER
MASSACHUSETTS
NOAA Chart: 13253 Latitude: 42° 5.0' N
USGS Quad: DUXBURY Longitude: 70° 38.8' W
To reach the tidal bench marks from the intersection of State Routes 3 and 14
(Exit 11 on State Route 3), proceed east on State Route 14 for 0.7 mile (1.1 km)
to State Route 139, then west on State Route 139 for 4.5 miles (7.2 km) to Town
Pier Road, turn right onto Town Pier Road and go SE for 0.7 mile (1.1 km) to
Brant Rock Town Pier. The bench marks are near the town pier, along State Route
139 at the bridge over Green River Harbor, and along the ocean sea wall in Brant
Rock (near the intersection of State Route 139 and Ocean Street). The tide
gauge and staff were near the midpoint of the Brant Rock Town Pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1972
MONUMENTATION: Survey Disk VM#: 1490
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Sea Wall
The bench mark is set in the sea wall at the west end of the Brant Rock Town
Pier parking lot, 26.0 feet (7.9 m) NNW of a flagpole, 26.0 feet (7.9 m) SSW of
power pole #P3, and 19.2 feet (5.9 m) NW of the NW corner of the Harbormaster's
office.
BENCH MARK STAMPING: NO 3 1972
MONUMENTATION: Survey Disk VM#: 1491
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Sea Wall
The bench mark is set in the sea wall at the west side of the Brant Rock Town
Pier parking lot, 92.2 feet (28.1 m) north of Bench Mark NO 1 1972, 35.4 feet
(10.8 m) SSW of light pole #43S and 4.3 feet (1.3 m) west of a steel guard rail.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 06/19/1991
Station ID: 8446009 SUPERCEDED DATE: 04/21/2003
Name: BRANT ROCK, GREEN HARBOR RIVER
MASSACHUSETTS
NOAA Chart: 13253 Latitude: 42° 5.0' N
USGS Quad: DUXBURY Longitude: 70° 38.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6009 A 1990
MONUMENTATION: Survey Disk VM#: 1492
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Bridge Abutment
The bench mark is set in the SW concrete abutment of the Town Pier Road bridge
over a small creek, 178 feet (54 m) SSW of the NW abutment, 13.4 feet (4.1 m)
WNW of the road centerline, 0.6 foot (0.2 m) SSW of the north face of the
abutment, and level with the road.
BENCH MARK STAMPING: 29 Q
MONUMENTATION: Survey Disk VM#: 1493
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Slab
The bench mark is set in the top slab of the SE side of the concrete sluiceway
over Green Harbor River, 16 feet (5 m) SE of the centerline of State Route 139,
3.8 feet (1.2 m) east of the west corner of the slab, and 2.9 feet (0.9 m)NW of
the edge of the slab.
BENCH MARK STAMPING: BRANT ROCK DATUM NO 2
MONUMENTATION: Survey Disk VM#: 1494
AGENCY: PID#: MY4009
SETTING CLASSIFICATION: Concrete Sea Wall
The bench mark is set in the sea wall behind the house at 508 Ocean Street, 36.0
feet (11.0 m) east of the SE corner of the house, 26.3 feet (8.0 m) NE of the NW
corner of the house, 0.4 foot (0.1 m) east of the west edge of the sea wall, and
2.6 feet (0.8 m) above back yard of the house.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 06/19/1991
Station ID: 8446009 SUPERCEDED DATE: 04/21/2003
Name: BRANT ROCK, GREEN HARBOR RIVER
MASSACHUSETTS
NOAA Chart: 13253 Latitude: 42° 5.0' N
USGS Quad: DUXBURY Longitude: 70° 38.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BRANT ROCK SEAWALL DATUM
MONUMENTATION: Survey Disk VM#: 1495
AGENCY: PID#: MY0078
SETTING CLASSIFICATION: Concrete Sea Wall
The bench mark is set in the concrete sea wall behind the house at 21 South
Street, 61.6 feet (18.8 m) NE of the south corner of the sea wall, 44.2 feet
(13.5 m) east of the NE corner of the house, 1.3 feet (0.4 m) west of the east
edge of the sea wall, and 1.3 feet (0.4 m) above the patio in the back yard of
the house.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 06/19/1991
Station ID: 8446009 SUPERCEDED DATE: 04/21/2003
Name: BRANT ROCK, GREEN HARBOR RIVER
MASSACHUSETTS
NOAA Chart: 13253 Latitude: 42° 5.0' N
USGS Quad: DUXBURY Longitude: 70° 38.8' W
T I D A L D A T U M S
Tidal datums at BRANT ROCK, GREEN HARBOR RIVER based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: JUNE - AUGUST 1990
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8443970 BOSTON
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (06/23/1990) = 12.04
MEAN HIGHER HIGH WATER MHHW = 9.93
MEAN HIGH WATER MHW = 9.49
MEAN TIDE LEVEL MTL = 4.92
MEAN LOW WATER MLW = 0.35
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (05/26/1990) = -1.61
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1972 14.65 5.16
NO 3 1972 14.57 5.08
6009 A 1990 17.53 8.04
29 Q 16.30 6.81
BRANT ROCK DATUM NO 2 21.05 11.56
BRANT ROCK SEAWALL DATUM 21.08 11.59
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 06/19/1991
Station ID: 8446009 SUPERCEDED DATE: 04/21/2003
Name: BRANT ROCK, GREEN HARBOR RIVER
MASSACHUSETTS
NOAA Chart: 13253 Latitude: 42° 5.0' N
USGS Quad: DUXBURY Longitude: 70° 38.8' 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.