U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 PUBLICATION DATE: 01/11/1982 Station ID: 8630249 SUPERCEDED DATE: 04/21/2003 Name: U.S.C.G STATION, CHINCOTEAGUE ISLAND VIRGINIA NOAA Chart: 12211 Latitude: 37° 55.9' N USGS Quad: CHINCOTEAGUE WEST Longitude: 75° 23.0' W To reach the tidal bench marks from the junction of State Highway 175 and Main Street in Chincoteague, proceed 0.3 mile southwest along Main Street, to the U.S. Coast Guard Base. The tide gage and staff were located at the northern edge of the U.S. Coast Guard south wharf at Chincoteague. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 2 1962 MONUMENTATION: Survey Disk VM#: 3253 AGENCY: PID#: FW0136 SETTING CLASSIFICATION: Concrete Post The bench mark is 200 feet west of the centerline of Main Street, 38 feet south of the north boundary (an east-west fence) of the Coast Guard Station, and at the base of a flag pole. The bench mark is set flush in concrete. BENCH MARK STAMPING: NO 3 1962 MONUMENTATION: Survey Disk VM#: 3254 AGENCY: PID#: FW0135 SETTING CLASSIFICATION: Concrete Porch The bench mark is set in a concrete porch, located 0.5 mile south of Chincoteague bridge (Virginia 175), just north of the Coast Guard Station driveway, 27 feet west of the centerline of Main Street and located on the southwest corner of the concrete porch of Conant Brothers Hardware Store.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 PUBLICATION DATE: 01/11/1982 Station ID: 8630249 SUPERCEDED DATE: 04/21/2003 Name: U.S.C.G STATION, CHINCOTEAGUE ISLAND VIRGINIA NOAA Chart: 12211 Latitude: 37° 55.9' N USGS Quad: CHINCOTEAGUE WEST Longitude: 75° 23.0' W T I D A L B E N C H M A R K S BENCH MARK STAMPING: TIDAL BM NO 1 1976 MONUMENTATION: Survey Disk VM#: 3255 AGENCY: PID#: FW0614 SETTING CLASSIFICATION: Concrete Retaining Wall The bench mark is set in the top of a concrete retaining wall at the U.S. Coast Guard Base, on the north side of a boat ramp, 1.8 feet from the north- west end of the wall (at the end of a wooden sidewalk), and 0.2 foot above ground. BENCH MARK STAMPING: TIDAL BM NO 4 1976 MONUMENTATION: Survey Disk VM#: 3256 AGENCY: PID#: FW0613 SETTING CLASSIFICATION: Concrete Post The bench mark is set in concrete, 37.5 feet northwest of the centerline of Main Street, 31.5 feet southeast of telephone pole No. NO 1 AH, 10.3 feet southwest of the centerline of an exit driveway, and 0.2 foot below ground. BENCH MARK STAMPING: T 421 1963 MONUMENTATION: Survey Disk VM#: 3257 AGENCY: PID#: FW0139 SETTING CLASSIFICATION: Concrete Post The bench mark is set in a concrete post from the junction of State Highway 175 and Main Street at Chincoteague, 1.0 mile southwest along Main Street, 67.5 feet west-northwest and across the street from the northwest corner of a pink, one-story, block house, 26 feet west of the centerline of Main Street, 5.5 feet north-northeast of power pole No. 34 H-6MX, and 0.2 foot above ground level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 PUBLICATION DATE: 01/11/1982 Station ID: 8630249 SUPERCEDED DATE: 04/21/2003 Name: U.S.C.G STATION, CHINCOTEAGUE ISLAND VIRGINIA NOAA Chart: 12211 Latitude: 37° 55.9' N USGS Quad: CHINCOTEAGUE WEST Longitude: 75° 23.0' W T I D A L D A T U M S Tidal datums at U.S.C.G STATION, CHINCOTEAGUE ISLAND based on: LENGTH OF SERIES: 1 YEAR TIME PERIOD: FEB 1977 - JAN 1978 TIDAL EPOCH: 1960-1978 CONTROL TIDE STATION: 8638610 Hampton Roads, Virginia Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET: MEAN HIGHER HIGH WATER MHHW = 1.85 MEAN HIGH WATER MHW = 1.71 MEAN TIDE LEVEL MTL = 0.90 * NATIONAL GEODETIC VERTICAL DATUM NGVD29 = 0.64 MEAN LOW WATER MLW = 0.09 MEAN LOWER LOW WATER MLLW = 0.00 * NGVD reference based on adjustment of 1973 and NOS levels of 1977. North American Vertical Datum (NAVD88) Bench Mark Elevation Information In FEET above: Stamping or Designation MLLW MHW NO 2 1962 4.84 3.13 NO 3 1962 5.42 3.71 TIDAL BM NO 1 1976 4.70 2.99 TIDAL BM NO 4 1976 4.53 2.82 T 421 1963 4.00 2.29
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 PUBLICATION DATE: 01/11/1982 Station ID: 8630249 SUPERCEDED DATE: 04/21/2003 Name: U.S.C.G STATION, CHINCOTEAGUE ISLAND VIRGINIA NOAA Chart: 12211 Latitude: 37° 55.9' N USGS Quad: CHINCOTEAGUE WEST Longitude: 75° 23.0' W 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 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.