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

                                                                                
Station ID: 8459338                         PUBLICATION DATE:  08/03/2004
Name:       BLOCK ISLAND HARBOR, OLD HARBOR                   
            RI
NOAA Chart: 13217                           Latitude:   41° 10.4' N (  41.17330)
USGS Quad:  BLOCK ISLAND                    Longitude:  71° 33.4' W ( -71.55670)


To reach the tidal bench marks from Point Judith or New London, CT, proceed by
ferry to the ferry terminal at Old Harbor on Block Island.  The bench marks are
in the harbor area and along Water Street.  The tide gage and staff were on the
NW side of the large pier of the ferry landing.


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


                 PRIMARY BENCH MARK STAMPING:  NO 4 1938
                         DESIGNATION:          845 9338 TIDAL 4

MONUMENTATION:           Bench Mark disk                       VM#:         2222
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  LW0927
SETTING CLASSIFICATION:  Stone foundation                      OPUS PID:        
LATITUDE:   41° 10.4' N (  41.17330)          LONGITUDE:  71° 33.5' W ( -71.55830)


The primary bench mark is a disk set in top at the east side of the stone
foundation of the Womens Christian Temperance Union statue in the center of the
intersection of Front, High, and Water Streets, near the SE corner of the base,
22.01 m (72.2 ft) SW of the SW porch corner of Chapel Cottage on Front Street,
17.40 m (57.1 ft) south of the south corner of a 3-story blue and white building
at the intersection of Front and Water Streets, and 13.47 m (44.2 ft) east of an
unnumbered power pole at the intersection of Water and High Streets, and at
ground level.

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

                                                                                
Station ID: 8459338                         PUBLICATION DATE:  08/03/2004
Name:       BLOCK ISLAND HARBOR, OLD HARBOR                   
            RI
NOAA Chart: 13217                           Latitude:   41° 10.4' N (  41.17330)
USGS Quad:  BLOCK ISLAND                    Longitude:  71° 33.4' W ( -71.55670)


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


                         BENCH MARK STAMPING:  9338 A 1987
                         DESIGNATION:          845 9338 A

MONUMENTATION:           Tidal Station disk                    VM#:         2223
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete loading platform             OPUS PID:        
LATITUDE:   41° 10.4' N (  41.17330)          LONGITUDE:  71° 33.5' W ( -71.55830)


The bench mark is a disk set in the NE corner of the Block Island Post Office
loading platform, 29.11 m (95.5 ft) SW of the centerline of Corn Neck Road,
10.12 m (33.2 ft) west of the NE corner of the post office, 0.82 m (2.7 ft) east
of the southernmost of two loading platform columns, and 0.64 m (2.1 ft) above
ground level.



                         BENCH MARK STAMPING:  9338 B 1987
                         DESIGNATION:          845 9338 B

MONUMENTATION:           Tidal Station disk                    VM#:         2224
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Concrete retaining wall               OPUS PID:        
LATITUDE:   41° 10.4' N (  41.17330)          LONGITUDE:  71° 33.5' W ( -71.55830)


The bench mark is a disk set in top of the north corner of the concrete
retaining wall in front of the National Hotel, 26.03 m (85.4 ft) north of the
center railing of the steps for the main entrance to the hotel, 16.61 m (54.5
ft) SE of the bottom step of the entrance to the Surf Hotel, 6.40 m (21.0 ft) SW
of the centerline of the bend in Water Street, 0.15 m (0.5 ft) west of a white
picket fence, and at sidewalk level.

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

                                                                                
Station ID: 8459338                         PUBLICATION DATE:  08/03/2004
Name:       BLOCK ISLAND HARBOR, OLD HARBOR                   
            RI
NOAA Chart: 13217                           Latitude:   41° 10.4' N (  41.17330)
USGS Quad:  BLOCK ISLAND                    Longitude:  71° 33.4' W ( -71.55670)


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


                         BENCH MARK STAMPING:  NO 2 1930
                         DESIGNATION:          845 9338 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:        16865
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  LW0930
SETTING CLASSIFICATION:  Concrete retaining wall               OPUS PID:        
LATITUDE:   41° 10.4' N (  41.17330)          LONGITUDE:  71° 33.5' W ( -71.55830)


The bench mark is a disk set in a concrete retaining wall in front of small
frame Mobil Marine Service building on Water Street, 31.33 m (102.8 ft) west of
the SW corner of the Ballard Restaurant, 28.65 m (94.0 ft) SE of the SW corner
of the Old Harbor Dock Office, 3.29 cm (10.8 ft) SE of the NW end of the wall at
the Mobil building entrance, and 0.97 m (3.2 ft) above ground level.

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

                                                                                
Station ID: 8459338                         PUBLICATION DATE:  08/03/2004
Name:       BLOCK ISLAND HARBOR, OLD HARBOR                   
            RI
NOAA Chart: 13217                           Latitude:   41° 10.4' N (  41.17330)
USGS Quad:  BLOCK ISLAND                    Longitude:  71° 33.4' W ( -71.55670)


                            T I D A L   D A T U M S 


Tidal datums at BLOCK ISLAND HARBOR, OLD HARBOR based on:

     LENGTH OF SERIES:      1 YEAR
     TIME PERIOD:           April 1988 - March 1989
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8452660 NEWPORT, NARRAGANSETT BAY


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

     HIGHEST OBSERVED WATER LEVEL (10/22/1988)         =  1.573
     MEAN HIGHER HIGH WATER                     MHHW   =  0.981
     MEAN HIGH WATER                            MHW    =  0.905
     MEAN TIDE LEVEL                            MTL    =  0.470
     MEAN SEA LEVEL                             MSL    =  0.446
     MEAN LOW WATER                             MLW    =  0.035
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (02/09/1989)         = -0.665

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     NO 4 1938                                   7.762    6.857
     9338 A 1987                                 3.306    2.401
     9338 B 1987                                 6.141    5.236
     NO 2 1930                                   3.224    2.319


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

                                                                                
Station ID: 8459338                         PUBLICATION DATE:  08/03/2004
Name:       BLOCK ISLAND HARBOR, OLD HARBOR                   
            RI
NOAA Chart: 13217                           Latitude:   41° 10.4' N (  41.17330)
USGS Quad:  BLOCK ISLAND                    Longitude:  71° 33.4' W ( -71.55670)


                             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.