U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8665111 PUBLICATION DATE: 07/21/2003 Name: SOUTH DEWEES ISLAND, DEWEES INLET SC NOAA Chart: 11521 Latitude: 32° 50.0' N ( 32.83330) USGS Quad: CAPERS INLET Longitude: 79° 43.6' W ( -79.72670) To reach the tidal bench marks proceed by boat to the SW side of Dewees Island. The bench marks are located along a dirt road leading NE from the creek. The tide gage and staff were located on a T-shaped pier on the SW side of Dewees Island, just north of Old House Creek in the channel between Dewees Island and Big Hill Marsh. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: S.D.I. NO 2 1975 DESIGNATION: 866 5101 S.D.I. TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 4138 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 32° 50.1' N ( 32.83555) LONGITUDE: 79° 43.7' W ( -79.72759) The primary bench mark is a disk located along the dirt road, 5 m (16 ft) NW of the centerline of the road, and 0.43 m (1.4 ft) SE of a metal witness post with sign. The bench mark is set 6 cm (0.2 ft) above ground level, crimped to the top of a copper-clad steel rod driven to an unspecified depth, and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8665111 PUBLICATION DATE: 07/21/2003 Name: SOUTH DEWEES ISLAND, DEWEES INLET SC NOAA Chart: 11521 Latitude: 32° 50.0' N ( 32.83330) USGS Quad: CAPERS INLET Longitude: 79° 43.6' W ( -79.72670) T I D A L B E N C H M A R K S BENCH MARK STAMPING: S.D.I. NO 4 1975 DESIGNATION: 866 5101 S.D.I. TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 4139 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper pipe OPUS PID: LATITUDE: 12° 50.0' N ( 12.83330) LONGITUDE: 79° 43.6' W ( -79.72670) The bench mark is a disk located 18.59 m (61.0 ft) SW of the dirt road leading to the beach, 11.58 m (38.0 ft) SE of the centerline of the dirt road leading to the center of the island, 2.68 m (8.8 ft) east of a 0.3 m (1 ft) diameter cedar tree, and 0.58 m (1.9 ft) NE of a metal witness post with sign. The bench mark is set at ground level, brazed to the top of a copper pipe and surrounded by soilcrete. BENCH MARK STAMPING: S.D.I. NO 5 1975 DESIGNATION: 866 5101 S.D.I. TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 4140 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper pipe OPUS PID: LATITUDE: 12° 50.0' N ( 12.83330) LONGITUDE: 79° 43.6' W ( -79.72670) The bench mark is a disk located 26.97 m (88.5 ft) north of bench mark S.D.I. NO 4 1975, 9.45 m (31.0 ft) NW of the centerline of the dirt road leading to the center of the island, 1.40 m (4.6 ft) SE of an oak tree, and 0.61 m (2.0 ft) NE of a metal witness post with sign. The bench mark is set 0.15 m (0.5 ft) above ground level, brazed to the top of a copper pipe and surrounded by soilcrete.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8665111 PUBLICATION DATE: 07/21/2003 Name: SOUTH DEWEES ISLAND, DEWEES INLET SC NOAA Chart: 11521 Latitude: 32° 50.0' N ( 32.83330) USGS Quad: CAPERS INLET Longitude: 79° 43.6' W ( -79.72670) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 5111 F 1982 DESIGNATION: 866 5101 F TIDAL MONUMENTATION: Tidal Station disk VM#: 4141 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Stainless steel rod OPUS PID: LATITUDE: 12° 50.0' N ( 12.83330) LONGITUDE: 79° 43.6' W ( -79.72670) The bench mark is a disk set in the front lawn of the caretaker's house, 123 m (403 ft) NE of bench mark S.D.I. NO 2 1975, 12.44 m (40.8 ft) SE of utility pole #141362, 1.89 m (6.2 ft) NE of a 0.46 m (1.5 ft) diameter palmetto tree, and 1.37 m (4.5 ft) south of a metal witness post with sign. The bench mark is set 6 cm (0.2 ft) below ground level, crimped to the top of a stainless steel rod driven 9.8 m (32 ft) to refusal, and encased in a 5-inch PVC pipe and concrete kickblock. BENCH MARK STAMPING: S.D.I. NO 1 1975 DESIGNATION: 866 5101 S.D.I. TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 17128 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 12° 50.0' N ( 12.83330) LONGITUDE: 79° 43.6' W ( -79.72670) The bench mark is a disk located near the pier, 2 m (8 ft) SE of the center of the turnaround in the dirt causeway road, 1.62 m (5.3 ft) NE of the end of the dock, and 0.58 m (1.9 ft) NW of a metal witness post. The bench mark is set 6 cm (0.2 ft) below ground level, crimped to the top of a unspecified rod and driven to an unspecified depth.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8665111 PUBLICATION DATE: 07/21/2003 Name: SOUTH DEWEES ISLAND, DEWEES INLET SC NOAA Chart: 11521 Latitude: 32° 50.0' N ( 32.83330) USGS Quad: CAPERS INLET Longitude: 79° 43.6' W ( -79.72670) T I D A L D A T U M S Tidal datums at SOUTH DEWEES ISLAND, DEWEES INLET based on: LENGTH OF SERIES: 1 YEAR TIME PERIOD: January 1976 - December 1976 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8665530 CHARLESTON, COOPER RIVER ENTRANCE Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (11/21/1976) = 2.185 MEAN HIGHER HIGH WATER MHHW = 1.671 MEAN HIGH WATER MHW = 1.555 MEAN SEA LEVEL MSL = 0.823 MEAN TIDE LEVEL MTL = 0.803 MEAN LOW WATER MLW = 0.052 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (02/07/1976) = -0.625 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW S.D.I. NO 2 1975 2.199 0.644 S.D.I. NO 4 1975 2.787 1.232 S.D.I. NO 5 1975 2.998 1.443 5111 F 1982 2.752 1.197 S.D.I. NO 1 1975 2.412 0.857 Foot Notes: Bench marks 5111 F 1982 and S.D.I. NO 1 1975 are based on one differential leveling connection and do not meet the quality control standards of the NOS. Therefore, caution should be used when deriving elevations for these marks.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8665111 PUBLICATION DATE: 07/21/2003 Name: SOUTH DEWEES ISLAND, DEWEES INLET SC NOAA Chart: 11521 Latitude: 32° 50.0' N ( 32.83330) USGS Quad: CAPERS INLET Longitude: 79° 43.6' W ( -79.72670) 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.