U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 Station ID: 8573903 PUBLICATION DATE: 04/30/2003 Name: TOWN POINT WHARF MARYLAND NOAA Chart: 12277 Latitude: 39° 30.2' N USGS Quad: NORTH EAST Longitude: 75° 55.0' W To reach the tidal bench marks from South Chesapeake City, proceed 5 km (3 mi) south on U.S. Highway 213 to Town Point Road, then 5.1 km (3.2 mi) west on Town Road to Hollywood Beach Road, turn right and go 1.5 km (0.9 mi) NW on a black top road to its end, bear left at the Y onto Gour Road. The bench marks are located along Gour Road. The tide gage and staff were located on Town Point Wharf. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 5 1972 DESIGNATION: 857 3903 TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 5896 AGENCY: National Ocean Survey (NOS) PID: SETTING CLASSIFICATION: Concrete slab The primary bench mark is a disk set flush in the SW corner of a concrete slab at the base of a 18 m (60 ft) tower in the center of the wharf, 8.69 m (28.5 ft) east of the west end of the wharf, and 7.47 m (24.5 ft) south of the north wall of the wharf. BENCH MARK STAMPING: M 130 1971 DESIGNATION: M 130 MONUMENTATION: Bench Mark disk VM#: 5895 AGENCY: US Coast and Geodetic Survey (USC&GS) PID#: JU1847 SETTING CLASSIFICATION: Copper-clad steel rod with baseplate The bench mark is a disk located 58.80 m (192.9 ft) NW of the centerline of the road leading SW to the North Bluff (this road is perpendicular to Gour Road), 8.90 m (29.2 ft) SW of the center of a large concrete street drain near the NE gate post, 6.77 m (22.2 m) south of the SW gate post for the gate across the road, 5.09 m (16.7 ft) SW of the centerline of Gour Road, 5.45 m (17.8 ft) SE of the twin trunk 5-feet diameter tree, and 5.58 m (18.3 ft) NW of the most southern of two 6x6-feet gate posts. The bench mark is set 6 cm (0.2 ft) below ground level, crimped to the top of a 1.22 m (4 ft) copper-clad steel rod attached to a metal base plate, and encased in a 4-inch steel pipe.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 Station ID: 8573903 PUBLICATION DATE: 04/30/2003 Name: TOWN POINT WHARF MARYLAND NOAA Chart: 12277 Latitude: 39° 30.2' N USGS Quad: NORTH EAST Longitude: 75° 55.0' W T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 2 1975 DESIGNATION: 857 3903 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 5898 AGENCY: National Ocean Survey (NOS) PID: SETTING CLASSIFICATION: Retaining walls The bench mark is a disk set flush in a concrete bulkhead in front of a private residence, 5.58 m (18.3 ft) west of the centerline of the road leading to the wharf, and 0.88 m (2.9 ft) west of the east end of the bulkhead. BENCH MARK STAMPING: 3903 A 1986 DESIGNATION: 857 3903 A TIDAL MONUMENTATION: Tidal Station disk VM#: 5899 AGENCY: National Ocean Service (NOS) PID: SETTING CLASSIFICATION: Stainless steel rod The bench mark is a disk located near Town Point Wharf at the end of Gour Road, 20.21 m (66.3 ft) SE of a telephone pole with a light on the north side of North Bluff Road, 9.75 m (32.0 ft) SE of the centerline of North Bluff Road, 7.74 m (25.4 ft) SW of the centerline of Gour Road, and 3.63 m (11.9 ft) SW of the most northerly mailbox post of eleven mailboxes. The bench mark is set 15 cm (0.5 ft) below ground level, crimped to the top of a stainless steel rod driven 9.1 m (30 ft) and encased in a 6-inch PVC pipe with a cap.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 Station ID: 8573903 PUBLICATION DATE: 04/30/2003 Name: TOWN POINT WHARF MARYLAND NOAA Chart: 12277 Latitude: 39° 30.2' N USGS Quad: NORTH EAST Longitude: 75° 55.0' W T I D A L D A T U M S Tidal datums at TOWN POINT WHARF based on: LENGTH OF SERIES: 7 YEARS TIME PERIOD: January 1987 - December 1993 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8574680 BALTIMORE, FORT MCHENRY, PATAPSCO RIVER Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (09/06/1979) = 2.024 MEAN HIGHER HIGH WATER (MHHW) = 0.817 MEAN HIGH WATER (MHW) = 0.721 MEAN TIDE LEVEL (MTL) = 0.390 MEAN SEA LEVEL (MSL) = 0.383 MEAN LOW WATER (MLW) = 0.059 MEAN LOWER LOW WATER (MLLW) = 0.000 LOWEST OBSERVED WATER LEVEL (04/05/1975) = -1.128 National Geodetic Vertical Datum (NGVD 29) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW NO 5 1972 2.209 1.488 M 130 1971 3.232 2.511 NO 2 1975 2.600 1.879 3903 A 1986 4.632 3.911
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 Station ID: 8573903 PUBLICATION DATE: 04/30/2003 Name: TOWN POINT WHARF MARYLAND NOAA Chart: 12277 Latitude: 39° 30.2' N USGS Quad: NORTH EAST Longitude: 75° 55.0' 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 (NAVD 88). NGVD 29 is a fixed datum adopted as a national standard geodetic reference for heights but is now considered superseded. NGVD 29 is sometimes referred to as Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National Geodetic Survey (NGS) data base via the World Wide Web at National Geodetic Survey. NAVD 88 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. NAVD 88 replaces NGVD 29 as the national standard geodetic reference for heights. Bench mark elevations relative to NAVD 88 are available from NGS through the World Wide Web at National Geodetic Survey. NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred to MLLW only when two or more of the bench marks listed have NAVD 88 elevations. The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal datums elevation table may differ slightly from NAVD 88 elevations listed for each bench mark in the NGS database.