U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8446009 PUBLICATION DATE: 02/05/2004
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 1.1 km (0.7 mi)
to State Route 139, then continue west on State Route 139 for 7.2 km (4.5 mi) to
Town Pier Road, then turn right and proceed SE for 1.1 km (0.7 mi) on Town Pier
Road to the 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 guage and staff were located 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
DESIGNATION: 844 6009 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 1490
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete sea wall
The primary bench mark is a disk set in the concrete seawall located at the west
end of the Brant Rock Town Pier parking lot, 8 m (26 ft) NNW of a flagpole, 8 m
(26 ft) SSW of power pole #P3, and 5.85 m (19.2 ft) NW of the NW corner of the
Harbormaster's office.
BENCH MARK STAMPING: NO 3 1972
DESIGNATION: 844 6009 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 1491
AGENCY: National Ocean Survey (NOS) PID:
SETTING CLASSIFICATION: Concrete sea wall
The bench mark is a disk set in the concrete seawall located at the west side of
the Brant Rock Town Pier parking lot, 28.10 m (92.2 ft) north of bench mark NO 1
1972, 10.79 m (35.4 ft) SSW of light pole #43S and 1.31 m (4.3 ft) west of a
steel guard rail.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8446009 PUBLICATION DATE: 02/05/2004
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
DESIGNATION: 844 6009 A
MONUMENTATION: Tidal Station disk VM#: 1492
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Concrete bridge abutment
The bench mark is a disk set in the SW concrete abutment of the Town Pier Road
bridge located over a small creek, 54 m (178 ft) SSW of the NW abutment, 4.08 m
(13.4 ft) WNW of the road centerline, 0.18 m (0.6 ft) SSW of the north face of
the abutment.
BENCH MARK STAMPING: 29 Q
DESIGNATION: 844 6009 BM 29 Q
MONUMENTATION: Bench Mark disk VM#: 1493
AGENCY: US Coast and Geodetic Survey (USC&GS) PID:
SETTING CLASSIFICATION: Concrete sluiceway
The bench mark is a disk set in the top slab of the SE side of the concrete
sluiceway over Green Harbor River, 5 m (16 ft) SE of the centerline of State
Route 139, 1.16 m (3.8 ft) east of the west corner of the slab, and 0.88 m (2.9
ft) NW of the edge of the slab.
BENCH MARK STAMPING: BRANT ROCK DATUM RM NO 2
DESIGNATION: BRANT ROCK DATUM 1940 RM2
MONUMENTATION: Reference Mark disk VM#: 1494
AGENCY: US Coast and Geodetic Survey (USC&GS) PID#: MY4009
SETTING CLASSIFICATION: Concrete sea wall
The bench mark is a disk set in the concrete seawall behind the house at 508
Ocean Street, 11 m (36 ft) east of the SE corner of the house, 8.02 m (26.3 ft)
NE of the NW corner of the house, 0.12 m (0.4 ft) east of the west edge of the
seawall, and 0.79 m (2.6 ft) above back yard of the house.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8446009 PUBLICATION DATE: 02/05/2004
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
DESIGNATION: BRANT ROCK SEAWALL DATUM
MONUMENTATION: Triangulation Station disk VM#: 1495
AGENCY: US Coast and Geodetic Survey (USC&GS) PID#: MY0078
SETTING CLASSIFICATION: Concrete sea wall
The bench mark is a disk set in the concrete seawall located behind the house at
21 South Street, 18.78 m (61.6 ft) NE of the south corner of the seawall, 13.47
m (44.2 ft) east of the NE corner of the house, 0.4 m (1.3 ft) west of the east
edge of the seawall, and 0.4 m (1.3 ft) 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
Station ID: 8446009 PUBLICATION DATE: 02/05/2004
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 1990 - August 1990
TIDAL EPOCH: 1983-2001
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) = 3.009
MEAN HIGH WATER (MHW) = 2.873
MEAN SEA LEVEL (MSL) = 1.508
MEAN TIDE LEVEL (MTL) = 1.490
MEAN LOW WATER (MLW) = 0.106
MEAN LOWER LOW WATER (MLLW) = 0.000
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 1 1972 4.419 1.546
NO 3 1972 4.394 1.521
6009 A 1990 5.296 2.423
29 Q 4.921 2.048
BRANT ROCK DATUM RM NO 2 6.369 3.496
BRANT ROCK SEAWALL DATUM 6.381 3.509
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8446009 PUBLICATION DATE: 02/05/2004
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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.