U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
To reach the tidal bench marks from the Essex Town Hall Public Library Building
on State Route 22, proceed NE for 0.3 km (0.2 mi) on SR 22 to the Y intersection
with State Route 133; then NW for 0.1 km (0.06 mi) to the intersection with
Spring Street; then NE for 0.1 km (0.06 mi) to the intersection with Dodge
Street; then SE for 0.6 km (0.4 mi) to the Essex River Marina. The tide gage
and staff were located near the eastern end of the main marina bulkhead and the
tidal bench marks are in the vicinity of the marina and the entrance roads.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1771 A 1994
DESIGNATION: 844 1771 A
MONUMENTATION: Tidal Station disk VM#: 1539
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The primary bench mark is a disk set on the property of the Essex Marina, 58.0 m
(190.3 ft) NNE of the eastern-most light pole at the entrance ramp to the
eastern-most floating pier, 32.50 m (106.6 ft) SE of the SE corner of the Essex
River Tour Shelter, 27.80 m (91.2 ft) east of the Marina Bulkhead, and 1.0 m
(3.3 ft) SE of a small lone cedar tree. The bench mark is 20 cm (0.7 ft) below
grade, crimped to a stainless steel rod driven 8.5 m (28 ft) to refusal, and
encased in a 6-inch PVC pipe and standard kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1771 B 1994
DESIGNATION: 844 1771 B
MONUMENTATION: Tidal Station disk VM#: 1540
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete pad OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a disk set in the concrete apron fronting the concrete service
building on the Essex Marina Property, 19.40 m (63.6 ft) SW of the NE corner of
the service building, 1.90 m (6.2 ft) NE of the SW same building, 0.70 m (2.3
ft) east of the west edge of the concrete apron, and 0.21 m (0.7 ft) west of the
west face of the building.
BENCH MARK STAMPING: 1771 C 1994
DESIGNATION: 844 1771 C
MONUMENTATION: Tidal Station disk VM#: 1541
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a disk set alongside the dirt road leading to the Essex
Marina, 41.0 m (134.5 ft) east of power pole No. 1654 on the NE side of the
road, 4.0 m (13.1 ft) NE of the centerline of the dirt road, and 4.0 m (13.1 ft)
NNW of power pole No. 1655. The bench mark is 21 cm (0.7 ft) below grade,
crimped to a stainless steel rod driven 4.9 m (16 ft) to refusal, and encased in
a 6-inch PVC pipe and standard kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1771 D 1994
DESIGNATION: 844 1771 D
MONUMENTATION: Tidal Station disk VM#: 1856
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a disk set in a rock outcrop on the north side of the dirt
road leading to the Essex Marina, 24.00 m (78.7 ft) NNW of power pole No.
2-1653, 23.10 m (75.8 ft) SE of power pole no. 39-5759, and 5.00 m (16.4 ft)
north of the centerline of dirt road.
BENCH MARK STAMPING: 1771 E 1994
DESIGNATION: 844 1771 E
MONUMENTATION: Tidal Station disk VM#: 1861
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete retaining wall OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a disk set in a concrete retaining wall at the intersection of
Route 133 and Spring Street, 18.20 m (59.7 ft) south of the north end of the
wall, 9.40 m (30.8 ft) north of power pole No. 34-1072-4, 7.80 m (25.6 ft) west
of the centerline of Route 133, and 0.1 m (0.3 ft) above grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: AG52
DESIGNATION: 844 1771 AG52
MONUMENTATION: Survey disk VM#: 1867
AGENCY: Massachusetts Department of Public Works
(MADPW) IDB PID#:
SETTING CLASSIFICATION: Granite step OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a disk set in the west corner of the first granite step at the
main entrance to the Essex Town Hall on Martin Street (State Route 22), 135 m
(443 ft) west along Martin Street from the centerline of Winthrop Street, and 25
m (82 ft) south of the centerline of Martin Street.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: 844 1771 (2233)
ALIAS: NO STAMPING 1
MONUMENTATION: Chiseled Square VM#: 1873
AGENCY: Unknown IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a chiseled square on a rock outcrop on the south side of
Eastern Avenue (State Route 133) just east of the intersection with Southern
Avenue, 14.30 m (46.9 ft) east of Telephone Pole No. 299S, 8.80 m (28.9 ft) west
of Telephone Pole No. 300S 1659, and 7.10 m (23.3 ft) south of the Eastern
Avenue centerline.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: 844 1771 (3564)
ALIAS: NO STAMPING 2
MONUMENTATION: Rivet VM#: 2015
AGENCY: Unknown IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 42° 37.9' N ( 42.63170) LONGITUDE: 70° 46.6' W ( -70.77670)
The bench mark is a rivet set in a rock outcrop on the south side of Eastern
Avenue just east of the intersection with Southern Avenue, 14.60 m (47.9 ft)
east of Telephone Pole No. 299S, 8.40 m (27.6 ft) west of Telephone Pole No.
300S 1659, and 7.30 m (24.0 ft) south of the Eastern Avenue centerline.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
T I D A L D A T U M S
Tidal datums at ESSEX, ESSEX RIVER based on:
LENGTH OF SERIES: 4 Months
TIME PERIOD: June 1994 - September 1994
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8443970 BOSTON, BOSTON HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.025
MEAN HIGH WATER MHW = 2.895
MEAN SEA LEVEL MSL = 1.550
MEAN TIDE LEVEL MTL = 1.495
MEAN LOW WATER MLW = 0.096
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1771 A 1994 3.738 0.843
1771 B 1994 4.374 1.479
1771 C 1994 3.396 0.501
1771 D 1994 6.320 3.425
1771 E 1994 9.641 6.746
AG52 9.176 6.281
844 1771 (2233) 7.311 4.416
844 1771 (3564) 7.390 4.495
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 8
Station ID: 8441771 PUBLICATION DATE: 04/21/2003
Name: ESSEX, ESSEX RIVER
MA
NOAA Chart: 13279 Latitude: 42° 37.9' N ( 42.63170)
USGS Quad: IPSWICH Longitude: 70° 46.6' W ( -70.77670)
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.