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.