U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
To reach the tidal bench marks from Interstate 95 heading north, take Exit 1
(State Highway 103) which is 0.6 mile (1.0 km) north of the Maine state line
continue on State Highway 103 for 1.4 miles (2.3 km) to the main gate of
Portsmouth Naval Shipyard. The bench marks are located on the shipyard
compound. The tide gage and staff are located at Berth 2. A security clearance
is required to enter Berth 2.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 21 1975
MONUMENTATION: Survey Disk VM#: 1982
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Bulkhead
The bench mark is set flush in the top of a concrete bulkhead in the NE corner
of a concrete and granite seawall adjacent to the NE corner of the tide house,
75.7 feet (23.1 m) SW of the SW corner of one story building No. TB-63, 35.8
feet (10.9 m) north of the north side of the tide house, 3.0 feet (0.9 m) NW of
the intersection of the granite and concrete bulkhead.
BENCH MARK STAMPING: 5 1928
MONUMENTATION: Survey Disk VM#: 1974
AGENCY: PID#: OC0514
SETTING CLASSIFICATION: Concrete Water Table
The bench mark is set in the top horizontal face of the water table on the south
face of Building No. 2, 95.0 feet (29.0 m) NNW of the NW corner of Building No.
115, 46.8 feet (14.3 m) east of the SW corner of Building No. 155, 5.5 feet (1.7
m) west of the SE corner of Building No. 2, and 1.9 feet (0.6 m) above the
pavement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6 1940
MONUMENTATION: Survey Disk VM#: 1975
AGENCY: PID#: OC0515
SETTING CLASSIFICATION: Granite Foundation
The bench mark is set in the top face of the granite foundation mat on the north
side of the NE corner of Building No. 2, 80.2 feet (24.4 m) south of the most
southeasterly point of Dry Dock # 1, 79.0 feet (24.1 m) SSW of the SW corner of
boiler pad at Dry Dock # 1, 3.2 feet (1.0 m) west of the white door with Danger
440 Volts sign on it, and 1.7 feet (0.5 m) west of the NE corner of the
building.
BENCH MARK STAMPING: 7 1940
MONUMENTATION: Survey Disk VM#: 1976
AGENCY: PID#: OC0516
SETTING CLASSIFICATION: Concrete Monolith
The bench mark is a standard disk set in the top face of a concrete monolith on
the east side of the SE corner of the new addition to Building No. 92, 104.5
feet (31.9 m) east of the SW corner of the new addition to Building No. 92, 74.6
feet (22.7 m) NW of the most northeasterly point of Dry Dock No. 1, 18.3 feet
(5.6 m) south of the most southerly track of railroad tracks leading to the new
addition of Building No. 92, and 2.1 feet (0.6 m) above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8 1940
MONUMENTATION: Survey Disk VM#: 1977
AGENCY: PID#: OC0517
SETTING CLASSIFICATION: Concrete Monolith
The bench mark is set in the top face of a concrete monolith on the west side of
the new addition to Building No. 92, 40.0 feet (12.2 m) north of the SW corner
at the building, 38.0 feet (11.6 m) SE of a barbed chain link fence on the west
side of Building No. 92, 11.4 feet (3.5 m) east of the most westerly brick face
of the new addition to Building No. 92, and 1.9 feet (0.6 m) above the parking
lot.
BENCH MARK STAMPING: #1 DD-1-D 1958
MONUMENTATION: Survey Disk VM#: 1978
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Sidewalk
The bench mark is set flush in a concrete sidewalk SE of the Marine Barracks,
61.0 feet (18.6 m) east of a fire hydrant in front of the Marine Barracks, 60.4
feet (18.4 m) west of the SW corner of a three car brick garage, (Building No.
M17) and 6.2 feet (1.9 m) NW of a concrete light pole.
BENCH MARK STAMPING: #2 DD-1-D 1958
MONUMENTATION: Survey Disk VM#: 1979
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Pad
The bench mark is set flush in a concrete pad between two cannons SE of the
Marine Barracks, 51.0 feet (15.5 m) SSE of the drive around the Marine Barracks,
9.5 feet (2.9 m) SW of the northern most cannon, and 5.4 feet (1.6 m) NW of the
southern most cannon.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 1A 1975
MONUMENTATION: Survey Disk VM#: 1980
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Manhole
The bench mark is set in the top of an octagonal concrete manhole, 14.8 feet
(4.5 m) north of the SW corner of Building No. 234, 12.5 feet (3.8 m) south of
the NW corner of Building 234, 10.0 feet (3.0 m) east of the west face of a
bulkhead, 4.0 feet (1.2 m) west of the east face of Building No. 234, and 2.1
feet (0.6 m) above the ground.
BENCH MARK STAMPING: NO 3 1975
MONUMENTATION: Survey Disk VM#: 1981
AGENCY: PID:
SETTING CLASSIFICATION: Step
The bench mark is set in the easterly of two 0.5 foot (0.2 m) high raised steps
on either side of the door at the north side of Building No. 162, 76.2 feet
(23.2 m) west of the NE corner of Building No. 162, 50.8 feet (15.5 m) south of
the centerline of Goodrich Ave., 11.1 feet (3.4 m) east of the NW corner of
Building No. 162, 2.9 feet (0.9 m) north of the building, and 0.6 foot (0.2 m)
above the pavement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO STAMPING 1
MONUMENTATION: Chiseled Triangle VM#: 1983
AGENCY: PID#: OC1289
SETTING CLASSIFICATION: Granite Water Table
The bench mark is a triangular cut on the NE corner of the granite water table
on Building No. 74, 64.9 feet (19.8 m) west of the NW corner of Building No. 59,
37.7 feet (11.5 m) SE of the SW corner of Building No. 130, 24.5 feet (7.5 m)
south of the SE corner of Building No. 130, and 1.5 feet (0.5 m) above the
ground. (NOTE: Bench mark historically referred to as NAVY 10.)
BENCH MARK STAMPING: NO STAMPING 2
MONUMENTATION: Square Cut VM#: 1984
AGENCY: PID#: OC0513
SETTING CLASSIFICATION: Concrete Step
The bench mark is a square cut on the second step at the NE entrance of Building
No. 13, 42.9 feet (13.1 m) east of the NW corner of Building No. 13, 15.0 feet
(4.6 m) south of the sidewalk on the north side of the building, 8.3 feet (2.5
m) west of the NE corner of Building No. 13, and 1.9 feet (0.6 m) above the
road. (NOTE: Bench mark historically referred to as NAVY 12.)
BENCH MARK STAMPING: NO STAMPING 3
MONUMENTATION: Chiseled Corner VM#: 1985
AGENCY: PID#: OC0518
SETTING CLASSIFICATION: Granite Water Table
The bench mark is cut away corner of the granite water table at the NE corner of
Building No. 89, 51.7 feet (15.8 m) SE of the NW corner of Building No. 115,
50.2 feet (15.3 m) SE of the NW corner of Building No. 89, 17.5 feet (5.3 m)
south of the SE corner of Building No. 115, and 0.7 feet (0.2 m) above the
ground. (NOTE: Bench mark historically referred to as NAVY 13.)
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
T I D A L D A T U M S
Tidal datums at PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU based on:
LENGTH OF SERIES: 9 YEARS
TIME PERIOD: 1974-76, 1979-85
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8418150 PORTLAND
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (02/07/1978) = 12.78
MEAN HIGHER HIGH WATER MHHW = 8.90
MEAN HIGH WATER MHW = 8.46
MEAN TIDE LEVEL MTL = 4.39
* NATIONAL GEODETIC VERTICAL DATUM NGVD29 = 4.11
MEAN LOW WATER MLW = 0.33
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/10/1977) = -3.00
* NGVD is based on elevations published in Quad 430703, Oct-1968 and
NOSleveling of 1979-86.
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 21 1975 12.97 4.51
5 1928 24.18 15.72
6 1940 14.58 6.12
7 1940 17.39 8.93
8 1940 17.45 8.99
#1 DD-1-D 1958 25.47 17.01
#2 DD-1-D 1958 24.20 15.74
NO 1A 1975 15.90 7.44
NO 3 1975 15.03 6.57
NO STAMPING 1 19.28 10.82
NO STAMPING 2 23.78 15.32
NO STAMPING 3 17.89 9.43
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
PUBLICATION DATE: 07/16/1987
Station ID: 8419870 SUPERCEDED DATE: 04/21/2003
Name: PORTSMOUTH NAVAL SHIPYARD, SEAVEY ISLAND, PORTSMOU
MAINE
NOAA Chart: 13283 Latitude: 43° 4.8' N
USGS Quad: KITTERY Longitude: 70° 44.5' W
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 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.