U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8459681 PUBLICATION DATE: 05/06/2003
Name: BLOCK ISLAND, SW END, BLOCK ISLAND SOUND
RI
NOAA Chart: 13217 Latitude: 41° 9.8' N ( 41.16330)
USGS Quad: BLOCK ISLAND Longitude: 71° 36.6' W ( -71.61000)
To reach the tidal bench marks from the ferry terminal in Old Harbor, Block
Island, proceed north on Water Street for 1.6 km (0.1 mi), then the road curves
left onto Dodge Street, continue west on Dodge Street for 0.3 km (0.2 mi) to a
four way stop intersection, then cross intersection and continue NW on Ocean
Avenue for 0.8 km (0.5 mi) to its intersection with Beach Avenue, follow arrow
indicating direction to New Harbor, turn NE on Beach Avenue, then left onto
Ocean Avenue for 0.3 km (0.2 mi) to its intersection with West Side Road, then
turn left on West Side Road, bear right at a cemetery and continue 4.5 km (2.8
mi) to the intersection of Cooneymus Road, turn right on Cooneymus Road and head
west to the beach. The bench marks are located along Cooneymus Road. The tide
gage orifice was located offshore of the foot of Cooneymus Road.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9681 B 1998
DESIGNATION: 845 9681 B
MONUMENTATION: Tidal Station disk VM#: 13966
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 41° 9.8' N ( 41.16330) LONGITUDE: 71° 36.6' W ( -71.61000)
The primary bench mark is a disk located 0.7 km (0.4 mi) from the intersection
of Cooneymus Road and West Side Road, on the north side of Conneymus Road, 10.80
m (35.4 ft) east of a utility pole with an electric meter attached on the west
side of the utility pole, 4.26 m (14.0 ft) north of the centerline of Cooneymus
Road, 12.44 m (40.8 ft) west of the centerline of the driveway located at 899
Cooneymus Road, and 3.53 m (11.6 ft) south of a witness post. The bench mark is
crimped to the top of a stainless rod driven 12.2 m (40 ft) to refusal, and
encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8459681 PUBLICATION DATE: 05/06/2003
Name: BLOCK ISLAND, SW END, BLOCK ISLAND SOUND
RI
NOAA Chart: 13217 Latitude: 41° 9.8' N ( 41.16330)
USGS Quad: BLOCK ISLAND Longitude: 71° 36.6' W ( -71.61000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9681 A 1998
DESIGNATION: 845 9681 A
MONUMENTATION: Flange-encased Rod VM#: 13965
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 41° 9.8' N ( 41.16330) LONGITUDE: 71° 36.6' W ( -71.61000)
The bench mark is a flange-encased rod located 0.7 km (0.4 mi) from the
intersection of Cooneymus Road and West Side Road, on the south side of
Conneymus Road, 19.80 m (65.0 ft) east of the center of the driveway leading to
a two story cedar shake dwelling, 28.10 m (92.2 ft) SW of a utility pole marked
"NET&CO 67", 4.75 m ( 15.6 ft) south of the centerline of Cooneymus Road, and
1.28 m (4.2 ft) north of a witness post. The datum point is the top of a
stainless rod driven 12.2 m (40 ft) to refusal, encased in a 1 m (3 ft) sleeve
and NOS logo cap.
BENCH MARK STAMPING: 9681 C 1998
DESIGNATION: 845 9681 C
MONUMENTATION: Flange-encased Rod VM#: 13967
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 41° 9.8' N ( 41.16330) LONGITUDE: 71° 36.6' W ( -71.61000)
The bench mark is a flange-encased rod located 0.56 km (0.35 mi) from the
intersection of Cooneymus Road and West Side Road, on the east side of Conneymus
Road, 3.65 m (12.0 ft) north of a utility pole marked "NET&CO 63", 4.29 m ( 14.1
ft) east of the centerline of Cooneymus Road, 10.39 m (34.1 ft) NE of a utility
pole on the west side of Conneymus Road marked "NET&CO ", and 0.85 m (2.8 ft)
west of a witness post. The datum point is the top of a stainless steel rod
driven 24.1 m (79 ft) to refusal, and encased in a 1 m (3 ft) sleeve and NOS
logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8459681 PUBLICATION DATE: 05/06/2003
Name: BLOCK ISLAND, SW END, BLOCK ISLAND SOUND
RI
NOAA Chart: 13217 Latitude: 41° 9.8' N ( 41.16330)
USGS Quad: BLOCK ISLAND Longitude: 71° 36.6' W ( -71.61000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9681 D 1998
DESIGNATION: 845 9681 D
MONUMENTATION: Tidal Station disk VM#: 13968
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 41° 9.8' N ( 41.16330) LONGITUDE: 71° 36.6' W ( -71.61000)
The bench mark is a disk located 0.24 km (0.15 mi) from the intersection of
Cooneymus Road and West Side Road, on the SW side of Conneymus Road, 32.60 m
(107.0 ft) SW of a utility pole marked "NET&CO 56", 15.50 m (50.8 ft) SE of a
utility pole on the north side of Cooneymus Road marked "NET&CO 57", 4.17 m (
13.7 ft) SW of the centerline of Cooneymus Road, and 0.55 m (1.8 ft) NE of a
witness post. The bench mark is crimped to the top of a stainless rod driven
6.7 m (22 ft) to refusal, and encased in a PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 9681 E 1998
DESIGNATION: 845 9681 E
MONUMENTATION: Flange-encased Rod VM#: 13969
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 41° 9.8' N ( 41.16330) LONGITUDE: 71° 36.6' W ( -71.61000)
The bench mark is a flange-encased rod located 0.08 km (0.05 mi) from the
intersection of Cooneymus Road and West Side Road, on the west side of Conneymus
Road, 39.68 m (130.2 ft) west of a utility pole marked "NET&CO 52", 4.90 m (16.4
ft) north of the centerline of Conneymus Road, 1.28 m (4.2 ft) east of a utility
pole marked "NET&CO 53", and 0.85 m (2.8 ft) south of a witness post. The datum
point is the top of a stainless rod driven 8.8 m (29 ft) to refusal, and encased
in a 1 m (3 ft) sleeve and NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8459681 PUBLICATION DATE: 05/06/2003
Name: BLOCK ISLAND, SW END, BLOCK ISLAND SOUND
RI
NOAA Chart: 13217 Latitude: 41° 9.8' N ( 41.16330)
USGS Quad: BLOCK ISLAND Longitude: 71° 36.6' W ( -71.61000)
T I D A L D A T U M S
Tidal datums at BLOCK ISLAND, SW END, BLOCK ISLAND SOUND based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: May 1998 - October 1998
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8452660 NEWPORT, NARRAGANSETT BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.900
MEAN HIGH WATER MHW = 0.826
MEAN TIDE LEVEL MTL = 0.431
MEAN SEA LEVEL MSL = 0.418
MEAN LOW WATER MLW = 0.035
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
9681 B 1998 5.123 4.297
9681 A 1998 7.056 6.230
9681 C 1998 6.096 5.270
9681 D 1998 15.369 14.543
9681 E 1998 17.463 16.637
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8459681 PUBLICATION DATE: 05/06/2003
Name: BLOCK ISLAND, SW END, BLOCK ISLAND SOUND
RI
NOAA Chart: 13217 Latitude: 41° 9.8' N ( 41.16330)
USGS Quad: BLOCK ISLAND Longitude: 71° 36.6' W ( -71.61000)
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.