U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 5
Station ID: 8418031 PUBLICATION DATE: 09/26/2003
Name: PORTLAND HEAD LIGHT STATION
ME
NOAA Chart: 13292 Latitude: 43° 37.4' N ( 43.62330)
USGS Quad: CAPE ELIZABETH Longitude: 70° 12.4' W ( -70.20670)
To reach the tidal bench marks from the South Portland proceed south 3.2 km (2
mi) along Shore Road to the Coast Guard Light Station at Portland Head. The
bench marks are located in the vicinity of the Light Station. The tide gage and
staff were located along the vertical cliff, east of the Light Station.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 8031 A 1979
DESIGNATION: 841 8031 A
MONUMENTATION: Tidal Station disk VM#: 1934
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete support OPUS PID:
LATITUDE: 43° 37.4' N ( 43.62330) LONGITUDE: 70° 12.4' W ( -70.20670)
The bench mark is a disk set flush in the SE corner concrete support of the
Coast Guard fog horn compressor shed located within the confines of the Portland
Head Coast Guard Light Station, 10.39 m (34.1 ft) ESE of the Portland Head
Lighthouse bearing ENE from the Ram Island Ledge Light, and 0.43 m (1.4 ft)
above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8418031 PUBLICATION DATE: 09/26/2003
Name: PORTLAND HEAD LIGHT STATION
ME
NOAA Chart: 13292 Latitude: 43° 37.4' N ( 43.62330)
USGS Quad: CAPE ELIZABETH Longitude: 70° 12.4' W ( -70.20670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8031 B 1979
DESIGNATION: 841 8031 B
MONUMENTATION: Tidal Station disk VM#: 1935
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge outcrop OPUS PID:
LATITUDE: 43° 37.4' N ( 43.62330) LONGITUDE: 70° 12.4' W ( -70.20670)
The bench mark is a disk set flush in a rock ledge outcrop on the northern side
of the Light Station located within the confines of the Portland Head Coast
Guard Light Station, 32.0 m (105 ft) WNW of bench mark 841 8031 A 1979, 15.09 m
(49.5 ft) NW of the intersection of the lighthouse and museum portion of the
station, 3.81 m (12.5 ft) NNW of the NE corner of the Coast Guard living
quarters bearing SW from the Ram Island Ledge Light.
BENCH MARK STAMPING: 8031 C 1979
DESIGNATION: 841 8031 C
MONUMENTATION: Tidal Station disk VM#: 1936
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge outcrop OPUS PID:
LATITUDE: 43° 37.4' N ( 43.62330) LONGITUDE: 70° 12.4' W ( -70.20670)
The bench mark is a disk set in a rock ledge outcrop west of the stations
automobile garage located within the confines of the Portland Head Coast Guard
Light Station, 26 m (85 ft) NW of bench mark 841 8031 B 1979, 13.56 m (44.5 ft)
NW of the NW corner of the Coast Guard living quarters, 8.08 m (26.5 ft) west of
the SW corner of the garage, and 7.47 m (24.5 ft) north of the centerline of the
driveway leading to the station.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8418031 PUBLICATION DATE: 09/26/2003
Name: PORTLAND HEAD LIGHT STATION
ME
NOAA Chart: 13292 Latitude: 43° 37.4' N ( 43.62330)
USGS Quad: CAPE ELIZABETH Longitude: 70° 12.4' W ( -70.20670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8031 D 1979
DESIGNATION: 841 8031 D
MONUMENTATION: Tidal Station disk VM#: 1937
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 43° 37.4' N ( 43.62330) LONGITUDE: 70° 12.4' W ( -70.20670)
The bench mark is a disk set in a rock outcrop on the south side of the Light
Station located within the confines of the Portland Head Coast Guard Light
Station, 30.02 m (98.5 ft) SSW of bench mark 841 8031 C 1979, 29 m (95 ft) NW of
the intersection of the south side of the station Museum building and the
lighthouse, 7.25 m (23.8 ft) SSW of the SW corner of the Coast Guard living
quarters, and 3.05 m (10.0 ft) north of the vertical cliff on the south side of
the station.
BENCH MARK STAMPING: 8031 E 1979
DESIGNATION: 841 8031 E
MONUMENTATION: Tidal Station disk VM#: 1938
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 43° 37.4' N ( 43.62330) LONGITUDE: 70° 12.4' W ( -70.20670)
The bench mark is a disk set in the SE corner of the concrete foundation of a
permament bicycle rack NE of the driveway leading to the Light Station located
within the confines of the Portland Head Light Station, 18.44 m (60.5 ft) NW of
bench mark 8031 C 1979, 18.44 m (24.5 ft) NE of the centerline of the driveway
leading to the station, and 4 m (12 ft) SW of the rock ledge that bench mark
8031 C 1979 is set in.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8418031 PUBLICATION DATE: 09/26/2003
Name: PORTLAND HEAD LIGHT STATION
ME
NOAA Chart: 13292 Latitude: 43° 37.4' N ( 43.62330)
USGS Quad: CAPE ELIZABETH Longitude: 70° 12.4' W ( -70.20670)
T I D A L D A T U M S
Tidal datums at PORTLAND HEAD LIGHT STATION based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: October 1979 - October 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 = 2.943
MEAN HIGH WATER MHW = 2.810
MEAN SEA LEVEL MSL = 1.466
MEAN TIDE LEVEL MTL = 1.456
MEAN LOW WATER MLW = 0.103
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
8031 A 1979 10.850 8.040
8031 B 1979 12.248 9.438
8031 C 1979 12.324 9.514
8031 D 1979 12.851 10.041
8031 E 1979 12.355 9.545
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8418031 PUBLICATION DATE: 09/26/2003
Name: PORTLAND HEAD LIGHT STATION
ME
NOAA Chart: 13292 Latitude: 43° 37.4' N ( 43.62330)
USGS Quad: CAPE ELIZABETH Longitude: 70° 12.4' W ( -70.20670)
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.