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Bench Mark Sheet for 8458694, WATCH HILL POINT RI

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                                                
Station ID: 8458694                         PUBLICATION DATE:  04/01/2004
Name:       WATCH HILL POINT                                  
            RI
NOAA Chart: 13214                           Latitude:   41° 18.3' N (  41.30500)
USGS Quad:  WATCH HILL                      Longitude:  71° 51.6' W ( -71.86000)


To reach the tidal bench marks from the city of Watch Hill proceed south 0.8 km
(0.5 mi) to the abandoned U.S. Coast Guard Watch Hill Station at Watch Hill
Point.  The bench marks are located in the area around the Coast Guard Station
and Watch Hill Point Lighthouse.  The gage and staff were located on a piling in
a small cove NW of the Coast Guard Station.  NOTE:  These bench mark
descriptions are based on September 10, 1962 recovery information.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  BM NO 2 1939
                         DESIGNATION:          845 8694 TIDAL 2

MONUMENTATION:           Bench Mark disk                       VM#:         2219
AGENCY:                  US Coast & Geodetic Survey
                         (USC&GS)                                 IDB PID#:  LW0809
SETTING CLASSIFICATION:  Step                                  OPUS PID:        
LATITUDE:   41° 18.3' N (  41.30500)          LONGITUDE:  71° 51.5' W ( -71.85830)


The primary bench mark is a disk set in the concrete base of the wooden steps at
the NW entrance door to the main Coast Guard Station Building, 5.30 m (17.4 ft)
NNE of the west corner of the building, and 0.12 m (0.4 ft) NE of the NE edge of
the bottom step.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 8458694                         PUBLICATION DATE:  04/01/2004
Name:       WATCH HILL POINT                                  
            RI
NOAA Chart: 13214                           Latitude:   41° 18.3' N (  41.30500)
USGS Quad:  WATCH HILL                      Longitude:  71° 51.6' W ( -71.86000)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  BM NO 1 1939
                         DESIGNATION:          845 8694 TIDAL 1

MONUMENTATION:           Bench Mark disk                       VM#:         2218
AGENCY:                  US Coast & Geodetic Survey
                         (USC&GS)                                 IDB PID#:  LW0810
SETTING CLASSIFICATION:  Concrete apron                        OPUS PID#: LW0810
LATITUDE:   41° 18.3' N (  41.30500)          LONGITUDE:  71° 51.5' W ( -71.85830)


The bench mark is a disk set in the concrete apron in the south corner of the
Coast Guard station garage at the gate entrance, 1 m (2 ft) SW of the SW edge of
the SW door of the garage, and 0.12 m (0.4 ft) NE of the SW edge of the apron.



                         BENCH MARK STAMPING:  BM NO 3 1939
                         DESIGNATION:          845 8694 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:         2220
AGENCY:                  US Coast & Geodetic Survey
                         (USC&GS)                                 IDB PID#:  LW0808
SETTING CLASSIFICATION:  Concrete sea wall                     OPUS PID:        
LATITUDE:   41° 18.2' N (  41.30330)          LONGITUDE:  71° 51.5' W ( -71.85830)


The bench mark is a disk set in the top of a concrete sea wall, 10.91 m (35.8
ft) NW of the north corner of the main building for the Watch Hill Point
lighthouse, 8 m (25 ft) north of a bend in the sea wall, and 4.48 m (14.7 ft) SW
of the top of the sea wall where the wall goes down to a lower level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 8458694                         PUBLICATION DATE:  04/01/2004
Name:       WATCH HILL POINT                                  
            RI
NOAA Chart: 13214                           Latitude:   41° 18.3' N (  41.30500)
USGS Quad:  WATCH HILL                      Longitude:  71° 51.6' W ( -71.86000)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  BM NO 4 1961
                         DESIGNATION:          845 8694 TIDAL 4

MONUMENTATION:           Bench Mark disk                       VM#:         2221
AGENCY:                  US Coast & Geodetic Survey
                         (USC&GS)                                 IDB PID#:        
SETTING CLASSIFICATION:  Concrete sea wall                     OPUS PID:        
LATITUDE:   41° 18.3' N (  41.30500)          LONGITUDE:  71° 51.4' W ( -71.85670)


The bench mark is a disk set in the western breakwater at the Coast Guard
Station, 88.79 m (291.3 ft) north of bench mark BM NO 3 1939, 75.71 m (248.4 ft)
SW of bench mark BM NO 2 1939, 11 m (35 ft) east of the approximate high water
mark, and 2.62 m (8.6 ft) south of the north end of the breakwater.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 8458694                         PUBLICATION DATE:  04/01/2004
Name:       WATCH HILL POINT                                  
            RI
NOAA Chart: 13214                           Latitude:   41° 18.3' N (  41.30500)
USGS Quad:  WATCH HILL                      Longitude:  71° 51.6' W ( -71.86000)


                            T I D A L   D A T U M S 


Tidal datums at WATCH HILL POINT based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           August 1962 - August 1962
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8461490 NEW LONDON, THAMES RIVER


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     MEAN HIGHER HIGH WATER                     MHHW   =  0.914
     MEAN HIGH WATER                            MHW    =  0.831
     North American Vertical Datum              NAVD88 =  0.553
     MEAN SEA LEVEL                             MSL    =  0.457
     MEAN TIDE LEVEL                            MTL    =  0.438
     MEAN LOW WATER                             MLW    =  0.045
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     BM NO 2 1939                                6.271    5.440
     BM NO 1 1939                                3.262    2.431
     BM NO 3 1939                                4.450    3.619
     BM NO 4 1961                                3.862    3.031


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                                                
Station ID: 8458694                         PUBLICATION DATE:  04/01/2004
Name:       WATCH HILL POINT                                  
            RI
NOAA Chart: 13214                           Latitude:   41° 18.3' N (  41.30500)
USGS Quad:  WATCH HILL                      Longitude:  71° 51.6' W ( -71.86000)


                             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.

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Products available at 8458694 WATCH HILL POINT, RI

Revised: 08/08/2018
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services