U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
Station ID: 8515586 PUBLICATION DATE: 10/30/2003
Name: NORTHPORT, NORTHPORT BAY
NY
NOAA Chart: 12365 Latitude: 40° 54.0' N ( 40.90000)
USGS Quad: NORTHPORT Longitude: 73° 21.2' W ( -73.35330)
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 8.9 km (5.5 mi) to
Route 25A in Huntington, turn right onto Route 25A and go east for 7.6 km (4.8
mi) to Church Street in the village of Northport, turn left onto Church Street
and go north for 1.3 km (0.8 mi) to Main Street, turn left again and go west for
0.8 km (0.5 mi) 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
DESIGNATION: 851 5586 RESET 1
MONUMENTATION: Tidal Station disk VM#: 5098
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: KU0449
SETTING CLASSIFICATION: Concrete landing OPUS PID:
LATITUDE: 40° 54.0' N ( 40.90000) LONGITUDE: 73° 21.2' W ( -73.35330)
The primary bench mark is a disk 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.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 8515586 PUBLICATION DATE: 10/30/2003
Name: NORTHPORT, NORTHPORT BAY
NY
NOAA Chart: 12365 Latitude: 40° 54.0' N ( 40.90000)
USGS Quad: NORTHPORT Longitude: 73° 21.2' W ( -73.35330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5586 A 1990
DESIGNATION: 851 5586 A
MONUMENTATION: Tidal Station disk VM#: 5099
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: concrete slab OPUS PID:
LATITUDE: 40° 54.0' N ( 40.90000) LONGITUDE: 73° 21.2' W ( -73.35330)
The bench mark is a disk set in an irregular slab of concrete on the north side
of the parking lot at Northport Village Dock, 38 m (125 ft) south of the village
park flagpole and near the south end of the rip-rap shoreline protection which
extends north of the parking lot, 5.43 m (17.8 ft) north of the north edge of
the paved parking surface, 3.81 m (12.5 ft) SW of the west edge of the paved
walk which runs along the water, and 1.62 m (5.3 ft) west of the face of the
west center upright of the northernmost of two dinghy racks on the west side of
the paved walk.
BENCH MARK STAMPING: 5586 B 1990
DESIGNATION: 851 5586 B
MONUMENTATION: Tidal Station disk VM#: 5100
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete slab OPUS PID:
LATITUDE: 40° 54.0' N ( 40.90000) LONGITUDE: 73° 21.2' W ( -73.35330)
The bench mark is a disk set in a 3 m x 4 m (9 ft x 12 ft) concrete slab which
extends west from the pump houses near the NE corner of the Northport Village
Dock parking lot, 10.97 m (36.0 ft) north of the NE corner of the
Bushnell/Demarest law office building, 2.59 m (8.5 ft) NW of the west face of
the pump house, 0.27 m (0.9 ft) east of the west edge of the slab, and 0.27 m
(0.9 ft) 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
Station ID: 8515586 PUBLICATION DATE: 10/30/2003
Name: NORTHPORT, NORTHPORT BAY
NY
NOAA Chart: 12365 Latitude: 40° 54.0' N ( 40.90000)
USGS Quad: NORTHPORT Longitude: 73° 21.2' W ( -73.35330)
T I D A L D A T U M S
Tidal datums at NORTHPORT, NORTHPORT BAY based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: June 1990 - August 1990
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8518490 NEW ROCHELLE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.392
MEAN HIGH WATER MHW = 2.285
MEAN SEA LEVEL MSL = 1.180
MEAN TIDE LEVEL MTL = 1.177
MEAN LOW WATER MLW = 0.069
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
RESET 1 1938 5.103 2.818
5586 A 1990 3.375 1.090
5586 B 1990 4.962 2.677
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 8515586 PUBLICATION DATE: 10/30/2003
Name: NORTHPORT, NORTHPORT BAY
NY
NOAA Chart: 12365 Latitude: 40° 54.0' N ( 40.90000)
USGS Quad: NORTHPORT Longitude: 73° 21.2' W ( -73.35330)
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.