U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
To reach the tidal bench marks from the intersection of State Routes 127 and
127A, proceed NE on State Route 127A (Broadway) for 0.6 km (0.4 mi) to Mount
Pleasant Street, then continue NE past Mount Pleasant Street for 0.2 km (0.1 mi)
to the parking lot for the T-wharf. The bench marks are in the vicinity of the
T-wharf, along Broadway, and on Bearskin Neck. The tide gauge and staff were on
the Sandy Bay Yacht Club pier.
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 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 10 1928
DESIGNATION: TIDAL 10 STA 8
MONUMENTATION: Tidal Station disk VM#: 11826
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: MY0231
SETTING CLASSIFICATION: Granite sidewalk curb OPUS PID:
LATITUDE: 42° 39.5' N ( 42.65830) LONGITUDE: 70° 37.0' W ( -70.61670)
The primary bench mark is a disk set in a granite curb near the intersection of
Broadway and Mount Pleasant Street, 24 m (79 ft) NNE of the north corner of
Rockport Baptist Church, 17.28 m (56.7 ft) WNW of power pole #1468, and 7.56 m
(24.8 ft) south of the centerline of Broad Street.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 11 1928
DESIGNATION: TIDAL 11 STA 8
MONUMENTATION: Tidal Station disk VM#: 11827
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Granite sidewalk curb OPUS PID:
LATITUDE: 42° 39.5' N ( 42.65830) LONGITUDE: 70° 36.9' W ( -70.61500)
The bench mark is a disk set in a granite curb in front of the brick School
Administration building on the north side of Broadway, 21.95 m (72.0 ft) SW of
the SE corner of the building, 16.18 m (53.1 ft) east of the SW corner of the
building, and 5.39 m (17.7 ft) north of the centerline of Broadway. Note: The
high point of the mark is along the west edge of the mark.
BENCH MARK STAMPING: 1551 A 1992
DESIGNATION: 844 1551 A
MONUMENTATION: Tidal Station disk VM#: 11828
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete retaining wall OPUS PID#: BBBJ40
LATITUDE: 42° 39.5' N ( 42.65830) LONGITUDE: 70° 36.9' W ( -70.61500)
The bench mark is a disk set in a 0.30 m x 0.40 m (1.0 ft x 1.3 ft) concrete
base along the north edge of the T-wharf, 25.30 m (83.0 ft) NW of the entrance
to Sandy Bay Yacht Club, 17.01 m (55.8 ft) WSW of the NE interior corner of the
T-wharf, 0.61 m (2.0 ft) NW of telephone pole #189, and 0.15 m (0.5 ft) above
the asphalt pavement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1551 B 1992
DESIGNATION: 844 1551 B
MONUMENTATION: Tidal Station disk VM#: 11829
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete base OPUS PID:
LATITUDE: 42° 39.5' N ( 42.65830) LONGITUDE: 70° 36.9' W ( -70.61500)
The bench mark is a disk set in the NW corner of a 0.40 m (1.3 ft) square
concrete base for the street sign at the intersection of South Street and
Donovans Corner on Bearskin Neck, 12.68 m (41.6 ft) SSW of telephone pole #1484,
7.50 m (24.6 ft) NE of a 0.61 m (2.0 ft) diameter granite post, and 0.76 m (2.5
ft) SW of the NW corner of the Lobster Shack.
BENCH MARK STAMPING: MOE 78
DESIGNATION: 841 1551 MOE
MONUMENTATION: Survey disk VM#: 11830
AGENCY: US Army Corps of Engineers (USE) IDB PID#:
SETTING CLASSIFICATION: Granite rock OPUS PID:
LATITUDE: 42° 39.5' N ( 42.65830) LONGITUDE: 70° 36.9' W ( -70.61500)
The bench mark is a disk set in a granite rock along the south side of a rotary
at the end of Bearskin Neck, 29 m (94 ft) SW of the center of the rock located
in the middle of the rotary at the end of Bearskin Neck, 7.44 m (24.4 ft) NE of
the NW corner of Old Stone Fort, 1.46 m (4.8 ft) SSE of the inner edge of the
curb, and 0.30 m (1.0 ft) above the road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: 844 1551 T 25
MONUMENTATION: Not specified (see descriptive text) VM#: 11831
AGENCY: Unknown IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 39.5' N ( 42.65830) LONGITUDE: 70° 36.9' W ( -70.61500)
The bench mark is a copper plug in a rock outcrop behind the New England
Telephone Company building at the intersection of Main and Hale Streets in
Rockport, 21 m (70 ft) south of the intersection, 10 m (33 ft) SW of the
centerline of Hale Street, and 5 m (17 ft) SE of the east corner of the
building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
T I D A L D A T U M S
Tidal datums at ROCKPORT HARBOR based on:
LENGTH OF SERIES: 2 Months
TIME PERIOD: August 1992 - September 1992
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 = 2.883
MEAN HIGH WATER MHW = 2.752
MEAN SEA LEVEL MSL = 1.436
MEAN TIDE LEVEL MTL = 1.426
MEAN LOW WATER MLW = 0.099
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 10 1928 5.495 2.743
NO 11 1928 6.517 3.765
1551 A 1992 4.709 1.957
1551 B 1992 5.083 2.331
MOE 78 8.817 6.065
844 1551 T 25 20.455 17.703
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8441551 PUBLICATION DATE: 04/21/2003
Name: ROCKPORT HARBOR
MA
NOAA Chart: 13279 Latitude: 42° 39.5' N ( 42.65830)
USGS Quad: ROCKPORT Longitude: 70° 36.9' W ( -70.61500)
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.