U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8418268 PUBLICATION DATE: 05/20/2004
Name: FORE RIVER, PORTLAND
ME
NOAA Chart: 13292 Latitude: 43° 38.5' N ( 43.64170)
USGS Quad: PORTLAND WEST Longitude: 70° 17.1' W ( -70.28500)
To reach the tidal bench marks, proceed to the Bancroft and Martin Oil Depot,
which is adjacent to the US Route 1 Highway Bridge connecting Portland and South
Portland, on the bank of the Fore River. The bench marks are located in the NE
corner of the depot near the docking facilities. The tide gage and staff were
located on the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 841 8268 A 1979
DESIGNATION: 841 8268 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 1949
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 43° 38.5' N ( 43.64170) LONGITUDE: 70° 17.1' W ( -70.28500)
The primary bench mark is a disk set flush in the concrete foundation supporting
the NW leg of a metal squasher, 6.0 m (19.7 ft) south of the centerline of the
road leading to the pier, 2.1 m (7.0 ft) east of the NE post of the docking
facilities sign which is adjacent to the squasher, and 0.2 m (0.5 ft) north of
the NW leg of the squasher.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8418268 PUBLICATION DATE: 05/20/2004
Name: FORE RIVER, PORTLAND
ME
NOAA Chart: 13292 Latitude: 43° 38.5' N ( 43.64170)
USGS Quad: PORTLAND WEST Longitude: 70° 17.1' W ( -70.28500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 841 8268 B 1979
DESIGNATION: 841 8268 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 1950
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 43° 38.5' N ( 43.64170) LONGITUDE: 70° 17.1' W ( -70.28500)
The bench mark is a disk set flush in the concrete foundation supporting a large
bollard, located in the NE corner of the depot, 9 m (30 ft) west of the
shoreline, 2.7 m (9.0 ft) north of the SW corner of the foundation, 1.5 m (5.0
ft) NW of the bollard, and 0.3 m (1.0 ft) south of the NW corner of the concrete
foundation.
BENCH MARK STAMPING: 841 8268 C 1979
DESIGNATION: 841 8268 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 1951
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete sewer tank OPUS PID:
LATITUDE: 43° 38.5' N ( 43.64170) LONGITUDE: 70° 17.1' W ( -70.28500)
The bench mark is a disk set flush in the NW corner of a concrete sewer tank
holding bin, located in the NE corner of the depot, 12.6 m (41.5 ft) NW of the
fire hydrant adjacent to the bin, 10.1 m (35 ft) west of the shoreline, 2.7 m
(8.9 ft) east of the NW corner of the bin, and 0.2 m (0.5 ft) west of the NE
corner of the bin.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8418268 PUBLICATION DATE: 05/20/2004
Name: FORE RIVER, PORTLAND
ME
NOAA Chart: 13292 Latitude: 43° 38.5' N ( 43.64170)
USGS Quad: PORTLAND WEST Longitude: 70° 17.1' W ( -70.28500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 841 8268 D 1979
DESIGNATION: 841 8268 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 1952
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 43° 38.5' N ( 43.64170) LONGITUDE: 70° 17.1' W ( -70.28500)
The bench mark is a disk set flush in the concrete foundation of a small metal
press, located in the NE corner of the depot, 7.8 m (25 ft) ESE of the railroad
tracks running through the road alongside the concrete foundation, 1.8 m (5.8
ft) north of the NW corner of the small shed located on the concrete foundation,
and 1.2 m (4.0 ft) south of the north side of the foundation.
BENCH MARK STAMPING: 841 8268 E 1979
DESIGNATION: 841 8268 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 1953
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete abutment OPUS PID:
LATITUDE: 43° 38.5' N ( 43.64170) LONGITUDE: 70° 17.1' W ( -70.28500)
The bench mark is a disk set flush in the south side of the railroad bridge
concrete abutment, located just outside the confines of the Bancroft and Martin
Oil Depot, 9.9 m (32.5 ft) south of the south edge of the Route 1 Highway bridge
west of the railroad bridge, 2.4 m (8.0 ft) west of the east side of the
abutment, and 1.1 m (3.5 ft) down from the top of the bridge on the lip
supporting the bridge braces.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8418268 PUBLICATION DATE: 05/20/2004
Name: FORE RIVER, PORTLAND
ME
NOAA Chart: 13292 Latitude: 43° 38.5' N ( 43.64170)
USGS Quad: PORTLAND WEST Longitude: 70° 17.1' W ( -70.28500)
T I D A L D A T U M S
Tidal datums at FORE RIVER, PORTLAND based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: September 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 = 3.034
MEAN HIGH WATER MHW = 2.899
MEAN SEA LEVEL MSL = 1.510
MEAN TIDE LEVEL MTL = 1.503
MEAN LOW WATER MLW = 0.106
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
841 8268 A 1979 5.766 2.867
841 8268 B 1979 5.005 2.106
841 8268 C 1979 4.782 1.883
841 8268 D 1979 5.545 2.646
841 8268 E 1979 6.060 3.161
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8418268 PUBLICATION DATE: 05/20/2004
Name: FORE RIVER, PORTLAND
ME
NOAA Chart: 13292 Latitude: 43° 38.5' N ( 43.64170)
USGS Quad: PORTLAND WEST Longitude: 70° 17.1' W ( -70.28500)
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.