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Superseded Bench Mark Sheet for 8515586, NORTHPORT, NORTHPORT BAY NY

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  4

                                                   PUBLICATION DATE:  02/11/1992
Station ID: 8515586                                SUPERCEDED DATE:   04/21/2003
Name:       NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND
            NEW YORK
NOAA Chart: 12365                                  Latitude:         40° 54.0' N
USGS Quad:  NORTHPORT                              Longitude:        73° 21.2' W


To reach the tidal bench marks from exit 40 North on the Long Island Expressway,
proceed north on Walt Whitman Road (State Highway 110) for 5.5 miles (8.9 km) to
Route 25A in Huntington, turn right onto Route 25A and go east for 4.75 miles
(7.64 km) to Church Street in the village of Northport, turn left onto Church
Street and go north for 0.75 mile (1.2 km) to Main Street, turn left again and
go west for 0.5 mile (0.8 km) to the end of Main Street at Northport Village
Dock.  The bench marks are in the park section adjacent to the dock and along
Main Street.  The tide gauge and staff were on the inshore corner of the L of
the dock.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  RESET 1 1938

MONUMENTATION:           Survey Disk                               VM#:     5098
AGENCY:                                                            PID#:  KU0449
SETTING CLASSIFICATION:  Concrete Landing


The primary bench mark is set in the top surface of the concrete landing at the
entrance to Chemical Bank at 56 Main Street, halfway between the building and
the edge of the landing, and between the two westernmost of four pillars in
front of the building.



                         BENCH MARK STAMPING:  5586 A 1990

MONUMENTATION:           Survey Disk                               VM#:     5099
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Irregular Concrete Slab


The bench mark is set in an irregular slab of concrete on the north side of the
parking lot at Northport Village Dock, about 125 feet (38 m) south of the
village park flagpole and near the south end of the rip-rap shoreline protection
which extends north of the parking lot, 17.8 ft (5.4 m) north of the north edge
of the paved parking surface, 12.5 ft (3.8 m) SW of the west edge of the paved
walk which runs along the water, and 5.3 ft (1.6 m) west of the face of the west
center upright of the northernmost of two dinghy racks located on the west side
of the paved walk.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  4

                                                   PUBLICATION DATE:  02/11/1992
Station ID: 8515586                                SUPERCEDED DATE:   04/21/2003
Name:       NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND
            NEW YORK
NOAA Chart: 12365                                  Latitude:         40° 54.0' N
USGS Quad:  NORTHPORT                              Longitude:        73° 21.2' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  5586 B 1990

MONUMENTATION:           Survey Disk                               VM#:     5100
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Slab


The bench mark is set in a 9 x 12-foot (3 x 4 m) concrete slab which extends
west from the pump houses near the NE corner of the Northport Village Dock
parking lot, 36.0 feet (11.0 m) north of the NE corner of the Bushnell/Demarest
law office building, 8.5 feet (2.6 m) NW of the west face of the pump house, 0.9
foot    (0.3 m) east of the west edge of the slab, and 0.9 foot (0.3 m) north of
the south edge of the slab.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  4

                                                   PUBLICATION DATE:  02/11/1992
Station ID: 8515586                                SUPERCEDED DATE:   04/21/2003
Name:       NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND
            NEW YORK
NOAA Chart: 12365                                  Latitude:         40° 54.0' N
USGS Quad:  NORTHPORT                              Longitude:        73° 21.2' W


                            T I D A L   D A T U M S 


Tidal datums at NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           JUNE-AUGUST 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)         =   9.64
     MEAN HIGHER HIGH WATER                     MHHW   =   7.84
     MEAN HIGH WATER                            MHW    =   7.48
     MEAN TIDE LEVEL                            MTL    =   3.86
     MEAN LOW WATER                             MLW    =   0.23
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (06/22/1990)         =  -0.58

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     RESET 1 1938                               16.89      9.41
     5586 A 1990                                11.22      3.74
     5586 B 1990                                16.43      8.95


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  4

                                                   PUBLICATION DATE:  02/11/1992
Station ID: 8515586                                SUPERCEDED DATE:   04/21/2003
Name:       NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND
            NEW YORK
NOAA Chart: 12365                                  Latitude:         40° 54.0' N
USGS Quad:  NORTHPORT                              Longitude:        73° 21.2' 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.

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Products available at 8515586 NORTHPORT, NORTHPORT BAY, NY

Revised: 08/08/2018
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