U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 04/26/1999
Station ID: 8420411 SUPERCEDED DATE: 04/21/2003
Name: DOVER, COCHECO RIVER
NEW HAMPSHIRE
NOAA Chart: 13285 Latitude: 43° 11.8' N
USGS Quad: DOVER EAST Longitude: 70° 52.2' W
To reach the tidal bench marks from the intersection of Washington Street and
Central Avenue (Route 108) in downtown Dover, proceed SE on Washington Street
for one block, turn left and continue on Main Street, bear right on Poplar
Street, then turn right on Cocheco Street and proceed to George's Marina. The
bench marks are along Cocheco Street and Washington Street. The tide gage was
located at the dock at George's Marina.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: D 50 RESET 1977
DESIGNATION: D 50 RESET 1977
MONUMENTATION: Bench Mark disk VM#: 13987
AGENCY: CGS PID#: OC1094
SETTING CLASSIFICATION: Bridge abutment
The primary bench mark is a disk set in the south abutment of the east end of
the Washington Street bridge over the Cocheco River in downtown Dover, 0.3 km
(0.2 mi) east of the Post Office on Washington Street, 9.8 m (32 ft) south of
the centerline of the street, 0.9 m (3 ft) south of a guardrail, and 0.3 m (1
ft) west of a brick wall.
BENCH MARK STAMPING: 0411 A 1998
DESIGNATION: 842 0411 A
MONUMENTATION: Bench Mark disk VM#: 13984
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Retaining wall
The bench mark is a disk set in the east end of the concrete retaining wall
along the north side of Cocheco Street near George's Marina, 0.2 km (0.1 mi)
east on Cocheco Street from its intersection with Portland Street, 13.65 m (44.8
ft) east of power pole No. 119-14, 4.58 m (15.0 ft) north of the centerline of
Cocheco Street, 0.74 m (2.4 ft) west of the east end of the wall, and 1 m (3.3
ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 04/26/1999
Station ID: 8420411 SUPERCEDED DATE: 04/21/2003
Name: DOVER, COCHECO RIVER
NEW HAMPSHIRE
NOAA Chart: 13285 Latitude: 43° 11.8' N
USGS Quad: DOVER EAST Longitude: 70° 52.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0411 B 1998
DESIGNATION: 842 0411 B
MONUMENTATION: Bench Mark disk VM#: 13985
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Concrete pad
The bench mark is a disk set in the SE corner of a concrete pad on the west side
of George's Marina Ships Store, 0.08 km (0.05 mi) east on Cocheco Street from
its intersection with Portland Street, 24.78 m (81.3 ft) SW of the SE corner of
the store, 18.20 m (59.7 ft) NE od power pole No. 119-9-52-2 on the south side
of Cocheco Street, and 1.88 m (6.2 ft) SSE of the SW corner of the store.
BENCH MARK STAMPING:
DESIGNATION: 842 0411 P7
MONUMENTATION: Survey disk VM#: 13986
AGENCY: City of Dover PID:
SETTING CLASSIFICATION: Sidewalk
The bench mark is a disk set in the middle of the sidewalk at the NE corner of
the intersection of Washington Street and Central Avenue, in front of the Bank
of New Hampshire, 6.35 m (20.8 ft) west of the SE corner of the bank entrance,
5.13 m (16.8 ft) SSW of the NE corner of the entrance, and 1.41 m (4.6 ft) SE of
a light pole.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 04/26/1999
Station ID: 8420411 SUPERCEDED DATE: 04/21/2003
Name: DOVER, COCHECO RIVER
NEW HAMPSHIRE
NOAA Chart: 13285 Latitude: 43° 11.8' N
USGS Quad: DOVER EAST Longitude: 70° 52.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: F 5 1933
DESIGNATION: F 5
MONUMENTATION: Bench Mark disk VM#: 13988
AGENCY: CGS PID#: OC0394
SETTING CLASSIFICATION: Large brick building
The bench mark is a disk set vertically in the north face of the New Hampshire
Department of Human Services building (four-storied brick, formerly the Masonic
Temple), near the intersection of Washington and Locust Streets, 11.0 m (36 ft)
east of the east curb of Locust Street, 8.81 m (28.9 ft) east of the NW corner
of the building, 3.7 m (12 ft) south of the south curb of Washington Street, and
1.34 m (4.4 ft) above the sidewalk.
BENCH MARK STAMPING: Y 1 1923 56.552
DESIGNATION: Y 1
MONUMENTATION: Bench Mark disk VM#: 13989
AGENCY: CGS PID#: OC0328
SETTING CLASSIFICATION: Large building
The bench mark is a disk set vertically in the east face of the U.S. Post Office
near the intersection of Washington and Walnut Streets, near the SE corner of
the stone foundation of the building, 11.89 m (39.0 ft) north of the north curb
of Washington Street, 6.7 m (22 ft) west of the west curb of Walnut Street, 0.6
m (2 ft) north of the SE corner of the building, 1.5 m (5 ft) above Walnut
Street, and 0.46 m (1.5 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 04/26/1999
Station ID: 8420411 SUPERCEDED DATE: 04/21/2003
Name: DOVER, COCHECO RIVER
NEW HAMPSHIRE
NOAA Chart: 13285 Latitude: 43° 11.8' N
USGS Quad: DOVER EAST Longitude: 70° 52.2' W
T I D A L D A T U M S
Tidal datums at DOVER, COCHECO RIVER based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: July 1998 - August 1998
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8418150 PORTLAND, CASCO BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (06/15/1998) = 3.342
MEAN HIGHER HIGH WATER MHHW = 2.337
MEAN HIGH WATER MHW = 2.222
North American Vertical Datum NAVD88 = 1.213
MEAN SEA LEVEL MSL = 1.190
MEAN TIDE LEVEL MTL = 1.151
MEAN LOW WATER MLW = 0.079
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (05/27/1998) = -0.254
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
D 50 RESET 1977 8.100 5.878
0411 A 1998 7.511 5.289
0411 B 1998 5.252 3.030
842 0411 P7 13.113 10.891
F 5 1933 16.005 13.783
Y 1 1923 56.552 18.250 16.028
Foot Notes:
June 1998 tide observations were not used in computing datums at this station
due to extreme river level conditions
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 04/26/1999
Station ID: 8420411 SUPERCEDED DATE: 04/21/2003
Name: DOVER, COCHECO RIVER
NEW HAMPSHIRE
NOAA Chart: 13285 Latitude: 43° 11.8' N
USGS Quad: DOVER EAST Longitude: 70° 52.2' 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.