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Administration National Ocean Service Datums Page Page 1 of 4 PUBLICATION DATE: 02/11/1992 Station ID: 8515586 SUPERCEDED DATE: 04/21/2003 Name: NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND NEW YORK NOAA Chart: 12365 Latitude: 40° 54.0' N USGS Quad: NORTHPORT Longitude: 73°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and Atmospheric Administration National Ocean Service Page 2 of 4 PUBLICATION DATE: 02/11/1992 Station ID: 8515586 SUPERCEDED DATE: 04/21/2003 Name: NORTHPORT HARBOR, NORTHPORT BAY, LONG ISLAND SOUND NEW YORK NOAA Chart: 12365 Latitude: 40° 54.0' N USGS Quad: NORTHPORT Longitude: 73°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.