U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 04/08/1992
Station ID: 8516761 SUPERCEDED DATE: 04/21/2003
Name: PORT WASHINGTON, MANHASSET BAY
NEW YORK
NOAA Chart: 12366 Latitude: 40° 49.9' N
USGS Quad: SEA CLIFF Longitude: 73° 42.2' W
To reach the tidal bench marks from the intersection of Port Washington
Boulevard and Main Street in Port Washington, proceed west on Main Street for
1.0 mile (1.6 km) to North Hempstead Town Dock which is on the north side of
the street. The bench marks are in the parking area for the dock. The tide
gauge and staff were in the NW corner of the wharf area.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: AIRWAY 1990
MONUMENTATION: Survey Disk VM#: 7065
AGENCY: PID#: AA9607
SETTING CLASSIFICATION: Concrete Monument Base
The primary bench mark is set in the concrete base of a monument commemorating
aviation history at the NW corner of North Hemp- stead Town Dock, 1.9 feet (0.6
m) north of the NW corner of the granite monument, 1.4 feet (0.4 m) SW of the NW
face of the concrete retaining wall, and 0.3 foot (0.1 m) west of the east face
of the base which supports the monument.
BENCH MARK STAMPING: 6761 A 1990
MONUMENTATION: Survey Disk VM#: 7066
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Pad
The bench mark is set in the NE corner of a 3.5-foot (1.1 m) square concrete pad
which is north of the north face of the office building of the North Hempstead
Town Dock, 12.8 feet (3.9 m) north of the SW corner of the building, 10.1
feet (3.1 m) SW of the NW corner of the building, and 3.3 feet (1.0 m) north of
the north face of the building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 04/08/1992
Station ID: 8516761 SUPERCEDED DATE: 04/21/2003
Name: PORT WASHINGTON, MANHASSET BAY
NEW YORK
NOAA Chart: 12366 Latitude: 40° 49.9' N
USGS Quad: SEA CLIFF Longitude: 73° 42.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6761 B 1990
MONUMENTATION: Survey Disk VM#: 7067
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Walk
The bench mark is set in the NE corner of a concrete landing which has five
steps leading north and five steps leading south from Main Street down to the
parking lot of North Hempstead Town Dock, 12.8 feet (3.9 m) west of the west
curb face of Main Street, 11.3 feet (3.4 m) north of the north face of a
decorative stone wall, and 0.9 foot (0.3 m) south of the south face of the stone
wall.
BENCH MARK STAMPING: 6761 C 1990
MONUMENTATION: Survey Disk VM#: 7068
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Retaining Wall
The bench mark is set in the SE corner of the concrete cap of the retaining wall
of the North Hempstead Town Dock parking lot at a point where the wall has a
short L-shaped leg which extends NE, 42.5 feet (13.0 m) SW of the parking lot
light pole, 3.6 feet (1.1 m) NE of the SW face of the retaining wall, 0.7 foot
(0.2 m) SW of the NE end of the retaining wall, and 0.7 foot (0.2 m) SE of the
NW face of the L-shaped leg of the wall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 04/08/1992
Station ID: 8516761 SUPERCEDED DATE: 04/21/2003
Name: PORT WASHINGTON, MANHASSET BAY
NEW YORK
NOAA Chart: 12366 Latitude: 40° 49.9' N
USGS Quad: SEA CLIFF Longitude: 73° 42.2' W
T I D A L D A T U M S
Tidal datums at PORT WASHINGTON, MANHASSET BAY based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: JUNE-JULY 1990
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8518490 NEW ROCHELLE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (08/20/1990) = 9.92
MEAN HIGHER HIGH WATER MHHW = 7.91
MEAN HIGH WATER MHW = 7.55
MEAN TIDE LEVEL MTL = 3.91
MEAN LOW WATER MLW = 0.27
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (06/22/1990) = -0.80
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
AIRWAY 1990 15.71 8.16
6761 A 1990 15.27 7.72
6761 B 1990 18.93 11.38
6761 C 1990 13.77 6.22
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 04/08/1992
Station ID: 8516761 SUPERCEDED DATE: 04/21/2003
Name: PORT WASHINGTON, MANHASSET BAY
NEW YORK
NOAA Chart: 12366 Latitude: 40° 49.9' N
USGS Quad: SEA CLIFF Longitude: 73° 42.2' 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.