U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 7
Station ID: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
To reach the tidal bench marks from South Portland, Maine via boat, proceed east
to Cushing Island, in the SW section of Casco Bay. The bench marks are located
on the north side of the island near the old Army pier. The tide gage and staff
were located on the NE side of the 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: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
DESIGNATION: TIDAL 1 STA 83
ALIAS: 1
MONUMENTATION: Tidal Station disk VM#: 1920
AGENCY: U.S Department of Defense (DOD) IDB PID#: OC0216
SETTING CLASSIFICATION: Concrete abutment OPUS PID:
LATITUDE: 43° 38.7' N ( 43.64500) LONGITUDE: 70° 11.9' W ( -70.19830)
The bench mark is a disk set flush in the top of concrete abutment at the NE end
of the pier, 3.7 m (12.0 ft) NE of the centerline of the pier, and 1.1 m (3.7
ft) NE of the SW end of the concrete abutment. (Note: Benchmark historically
known as 1)
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: TIDAL 2 STA 83
ALIAS: 2
MONUMENTATION: Rivet VM#: 1921
AGENCY: US Coast & Geodetic Survey
(USC&GS) IDB PID#: OC0215
SETTING CLASSIFICATION: Concrete manhole OPUS PID:
LATITUDE: 43° 38.7' N ( 43.64500) LONGITUDE: 70° 11.9' W ( -70.19830)
The bench mark is a monel rivet set flush in top of a concrete manhole, 27.4 m
(90 ft) NE of the east concrete abutment of the pier, 13.1 m (43 ft) SE of the
centerline of the road leading to the post office, 5.4 m (17.8 ft) SE of the
seawall, 0.4 m (1.3 ft) north of the SE corner of the manhole, and set 0.3 m (1
ft) above ground level. (Note: Benchmark historically known as 2)
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: TIDAL 3 STA 83
ALIAS: 3
MONUMENTATION: Rivet VM#: 1922
AGENCY: US Coast & Geodetic Survey
(USC&GS) IDB PID#: OC0217
SETTING CLASSIFICATION: Concrete manhole OPUS PID:
LATITUDE: 43° 38.7' N ( 43.64500) LONGITUDE: 70° 11.9' W ( -70.19830)
The bench mark is a monel rivet set flush in top of a concrete manhole on the
north side of the brick mule barn located NW of the pier, 26.7 m (87.5 ft) NW of
the NW end of the pier, 8.3 m (27.3 ft) SW of the centerline of the road leading
to the pier, 1.2 m (4.1 ft) SW of the north wall of the building, and set 0.2 m
(0.5 ft) above ground level. (Note: Benchmark historically known as 3)
BENCH MARK STAMPING: 841 7997 D 1979
DESIGNATION: 841 7997 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 1923
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 43° 38.7' N ( 43.64500) LONGITUDE: 70° 11.9' W ( -70.19830)
The bench mark is set flush in the top of a seawall north of the end of the
pier, 40.6 feet (12.4 m) NW of the Bench Mark 2, (a monel rivet), 25.3 feet (7.7
m) SE of the centerline of the paved road, 12.3 feet (3.8 m) NW of the shore
line, and 6.8 feet (2.1 m) west of a 1 ft square block of granite located in the
sea wall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 841 7997 E 1979
DESIGNATION: 841 7997 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 1924
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Cconcrete step OPUS PID:
LATITUDE: 43° 38.7' N ( 43.64500) LONGITUDE: 70° 11.9' W ( -70.19830)
The bench mark is set flush in the second step of a cement staircase leading to
a red wood house on the north side of the paved road, leading to the pier, 12.3
feet (3.8 m) NW of the centerline of the paved road, 5.3 feet (1.6 m) SE of the
south corner of the red brick house support structure, and 0.8 foot (0.2 m) east
of the corner of the second stair.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
T I D A L D A T U M S
Tidal datums at CUSHING ISLAND, CASCO BAY based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: September 1979 - September 1979
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8418150 PORTLAND, CASCO BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.988
MEAN HIGH WATER MHW = 2.858
MEAN SEA LEVEL MSL = 1.493
MEAN TIDE LEVEL MTL = 1.483
North American Vertical Datum NAVD88 = 1.403
MEAN LOW WATER MLW = 0.108
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
TIDAL 1 STA 83 5.019 2.161
TIDAL 2 STA 83 3.894 1.036
TIDAL 3 STA 83 6.054 3.196
841 7997 D 1979 5.330 2.472
841 7997 E 1979 7.583 4.725
Foot Notes:
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8417997 PUBLICATION DATE: 05/20/2004
Name: CUSHING ISLAND, CASCO BAY
ME
NOAA Chart: 13290 Latitude: 43° 38.7' N ( 43.64500)
USGS Quad: PORTLAND EAST Longitude: 70° 11.9' W ( -70.19830)
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.