U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 Station ID: 8452944 PUBLICATION DATE: 05/20/2020 Name: CONIMICUT LIGHT, NARRAGANSETT BAY RI NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667) USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333) To reach the Conimicut Light tidal station head north in boat towards providence, RI, lighthouse is just south of the city in the Narragansett Bay. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: DESIGNATION: 845 2944 BOLT ALIAS: BOLT MONUMENTATION: Bolt VM#: 16300 AGENCY: National Ocean Service (NOS) IDB PID: SETTING CLASSIFICATION: Steel bolt OPUS PID: LATITUDE: 41° 43.0' N ( 41.71697) LONGITUDE: 71° 20.7' W ( -71.34508) The primary bench mark is a steel bolt with a chiseled X in the top of it, located on the south side of the lighthouse in the third handrail pole from the catwalk, 4.22 m (13.8 ft) south of the south side of handrail, 1.22 m (4.0 ft) SE of the side of the lighthouse, and 0.05 m (0.2 ft) NE of the bottom outer steel bulkhead around the lighthouse. BENCH MARK STAMPING: DESIGNATION: 845 2944 SRM MONUMENTATION: Chiseled Square VM#: 16017 AGENCY: National Ocean Service (NOS) IDB PID: SETTING CLASSIFICATION: Metal pier I-beam OPUS PID: LATITUDE: 41° 43.0' N ( 41.71708) LONGITUDE: 71° 20.7' W ( -71.34511) The bench mark is a chiseled square at the NW corner of the catwalk to the lighthouse, 7.65 m (25.1 ft) north of the north side of the lighthouse base, 1.80 m (5.9 ft) NW of the 4" protective well, and 1.45 m (4.8 ft) NNW of the SE corner of the walkway.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 Station ID: 8452944 PUBLICATION DATE: 05/20/2020 Name: CONIMICUT LIGHT, NARRAGANSETT BAY RI NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667) USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 2944 A 2004 DESIGNATION: 845 2944 A MONUMENTATION: Tidal Station disk VM#: 17662 AGENCY: National Ocean Service (NOS) IDB PID: SETTING CLASSIFICATION: Lighthouse foundation OPUS PID: LATITUDE: 41° 43.0' N ( 41.71697) LONGITUDE: 71° 20.7' W ( -71.34511) The bench mark is a disk set in the concrete walkway around the lighthouse near the top of the stairs, 7.95 m (26.1 ft) south of the north end of the catwalk leading to the lighthouse, 4.03 m (13.2 ft) NNE of the center of the door leading into the lighthouse, and 0.98 m (3.2 ft) north of the lighthouse wall. BENCH MARK STAMPING: 2944 B 2004 DESIGNATION: 845 2944 B MONUMENTATION: Tidal Station disk VM#: 17663 AGENCY: National Ocean Service (NOS) IDB PID: SETTING CLASSIFICATION: Concrete walkway OPUS PID: LATITUDE: 41° 43.0' N ( 41.71694) LONGITUDE: 71° 20.7' W ( -71.34508) The bench mark is a disk set in the concrete walkway around the lighthouse, 1.80 m (5.9 ft) SSW of the center of the three solar panels mounted on the handrail, 0.79 m (2.6 ft) ESE of the lighthouse wall, and 0.50 m (1.6 ft) WNW of the outer edge of the lighthouse base.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 Station ID: 8452944 PUBLICATION DATE: 05/20/2020 Name: CONIMICUT LIGHT, NARRAGANSETT BAY RI NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667) USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333) T I D A L D A T U M S Tidal datums at CONIMICUT LIGHT, NARRAGANSETT BAY based on: LENGTH OF SERIES: 15 YEARS TIME PERIOD: 8/01-7/09,5/10-4/12,6/12-5/13,9/13-8/14,4/15-3/18 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8454000 PROVIDENCE, PROVIDENCE RIVER Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (10/29/2012) = 2.743 MEAN HIGHER HIGH WATER MHHW = 1.398 MEAN HIGH WATER MHW = 1.322 MEAN TIDE LEVEL MTL = 0.687 MEAN SEA LEVEL MSL = 0.642 MEAN LOW WATER MLW = 0.052 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (02/11/2001) = -0.851 Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 845 2944 BOLT 4.882 3.560 845 2944 SRM 3.108 1.786 2944 A 2004 4.882 3.560 2944 B 2004 4.892 3.570
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 Station ID: 8452944 PUBLICATION DATE: 05/20/2020 Name: CONIMICUT LIGHT, NARRAGANSETT BAY RI NOAA Chart: 13221 Latitude: 41° 43.0' N ( 41.71667) USGS Quad: BRISTOL Longitude: 71° 20.6' W ( -71.34333) 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.