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Datums Page Page 1 of 5
Station ID: 8441241 PUBLICATION DATE: 10/26/2010
Name: PLUM IS. SOUTH END
MA
NOAA Chart: 13278 Latitude: 42° 42.6' N ( 42.71014)
USGS Quad: lpswich Longitude: 70° 47.3' W ( -70.78861)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
DESIGNATION: 844 1241 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 19593
AGENCY: USGS IDB PID#:
SETTING CLASSIFICATION: Bedrock outcrop OPUS PID:
LATITUDE: 42° 42.6' N ( 42.71028) LONGITUDE: 70° 47.3' W ( -70.78889)
The primary bench mark is a disk set in exposed bedrock in the lawn west of the
house, 57.67 m (189.2 ft) WSW of bench mark TIDAL 2, 17.18 m (56.4 ft) west of
western corner of house, 13.65 m (44.8 ft) NNW of center of stone step path down
to ramp and beach, 2.95 m (9.7 ft) NE of the top edge of bluff down to beach and
0.02 m (0.07 ft) below grade.
BENCH MARK STAMPING:
DESIGNATION: 844 1241 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 19594
AGENCY: USGS IDB PID#:
SETTING CLASSIFICATION: Bedrock outcrop OPUS PID#: BBBV25
LATITUDE: 42° 42.6' N ( 42.71053) LONGITUDE: 70° 47.3' W ( -70.78839)
The bench mark is set in exposed bedrock in the lawn northeast of the house and
shed, 57.67 m (189.2 ft) ENE of bench mark TIDAL 1, 54.97 m (180.3 ft) NNW of
the centerline of the road where it meets the lawn, 34.19 m (112.2 ft) NE of the
northern most corner of house, 13.01 m (42.7 ft) south of the northern top edge
of bluff down to beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8441241 PUBLICATION DATE: 10/26/2010
Name: PLUM IS. SOUTH END
MA
NOAA Chart: 13278 Latitude: 42° 42.6' N ( 42.71014)
USGS Quad: lpswich Longitude: 70° 47.3' W ( -70.78861)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO. 4 1949
DESIGNATION: 844 1241 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 19595
AGENCY: USGS IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 42° 42.6' N ( 42.71053) LONGITUDE: 70° 47.3' W ( -70.78900)
The bench mark is set near the top of a giant 3.25 m x 4.82 m x 2.64 m (10.6 ft
x 15.8 ft x 8.6 ft) boulder resting on the northwestern bluff down to the beach,
31.28 m (102.6 ft) NNW of the western corner of the house, 28.69 m (94.1 ft)
north of bench mark TIDAL 1, 3.64 m (11.9 ft) NW of the top of the northwestern
edge of bluff down to beach, 0.90 m (3.0 ft) below level of lawn.
BENCH MARK STAMPING: 1241 A 2010
DESIGNATION: 844 1241 A
MONUMENTATION: Tidal Station disk VM#: 19596
AGENCY: NOS IDB PID#:
SETTING CLASSIFICATION: Outcrop OPUS PID:
LATITUDE: 42° 42.6' N ( 42.71022) LONGITUDE: 70° 47.3' W ( -70.78806)
The bench mark is set flush in exposed bedrock in the lawn west of the point
where the road meets the lawn, 41.48 m (136.1 ft) SSE of bench mark 8441241
TIDAL 2, 41.47 m (136.0 ft) east of the eastern most corner of house, 8.15 m
(26.7 ft) NW of the center of road where if meets the lawn, and 7.88 m (25.9 ft)
NE of the top of the southern edge of the bluff down to beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8441241 PUBLICATION DATE: 10/26/2010
Name: PLUM IS. SOUTH END
MA
NOAA Chart: 13278 Latitude: 42° 42.6' N ( 42.71014)
USGS Quad: lpswich Longitude: 70° 47.3' W ( -70.78861)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1241 B 2010
DESIGNATION: 844 1241 B
MONUMENTATION: Tidal Station disk VM#: 19597
AGENCY: NOS IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 42° 42.6' N ( 42.71031) LONGITUDE: 70° 47.2' W ( -70.78711)
The bench mark is set flush in the top of a 0.95 m x 2.05 m x 1.30 m (3.1 ft x
6.7 ft x 4.3 ft) boulder partially buried in the short bluff down to stone beach
along the road to the house at the end of the point, 83.89 m (275.2 ft) ESE of
bench mark 8441241 A, 26.71 m (87.6ft) WNW of a 1.90 m (6.2 ft) tall US Fish &
Wildlife Service "Area Closed" sign along the dirt/grass road to the point, 4.95
m (16.2 ft) SW of the centerline of the dirt/grass road to the end of the point
and 0.35 m (1.1 ft) below the surface of road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8441241 PUBLICATION DATE: 10/26/2010
Name: PLUM IS. SOUTH END
MA
NOAA Chart: 13278 Latitude: 42° 42.6' N ( 42.71014)
USGS Quad: lpswich Longitude: 70° 47.3' W ( -70.78861)
T I D A L D A T U M S
Tidal datums at PLUM IS. SOUTH END based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: May 2010 - July 2010
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 = 2.892
MEAN HIGH WATER MHW = 2.769
MEAN TIDE LEVEL MTL = 1.432
MEAN SEA LEVEL MSL = 1.429
MEAN LOW WATER MLW = 0.095
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
844 1241 TIDAL 1 6.538 3.769
844 1241 TIDAL 2 6.497 3.728
NO. 4 1949 5.581 2.812
1241 A 2010 6.723 3.954
1241 B 2010 4.783 2.014
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8441241 PUBLICATION DATE: 10/26/2010
Name: PLUM IS. SOUTH END
MA
NOAA Chart: 13278 Latitude: 42° 42.6' N ( 42.71014)
USGS Quad: lpswich Longitude: 70° 47.3' W ( -70.78861)
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.