U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 01/22/1988
Station ID: 8571901 SUPERCEDED DATE: 04/21/2003
Name: AVALON, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12266 Latitude: 38° 42.7' N
USGS Quad: TILGHMAN Longitude: 76° 20.1' W
To reach the tidal bench marks from Knapps Narrows Bridge on Tilghman Island,
proceed south on State Road 33 for 0.8 mile (1.3 km) to Wharf Street, turn left
onto Wharf Street and continue 0.5 mile (0.8 km) to the end of the pier. The
bench marks are located at the seaward end of the pier around the abandoned
Skipjack Restaurant and around the abandoned factory located south of Wharf
Street at the waterfront. The tide gage and staff were located on a dock
(Harrison's Chesapeake House) east of a hotel and restaurant and north of Wharf
Street.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1901 A 1983
MONUMENTATION: Survey Disk VM#: 3070
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Seawall
The bench mark is in the east seawall of Avalon Pier, 201.3 feet (61.4 m) ENE of
Bench Mark 1901 B 1983, 178.3 feet (54.3 m) NE of the NE corner of the abandoned
Skipjack Restaurant, 132.7 feet (40.4 m) ENE of the NE corner of the easternmost
cinderblock shed on the north side of the restaurant, 112.5 feet (34.3 m) north
of the asphalt-concrete interface on the pier, 67.7 feet (20.6 m) south of
the east end of the north wood bulkhead, 1.8 feet (0.5 m) north of a raised
section of the eastern seawall, 0.5 foot (0.2 m) west of the east edge of the
seawall, and at ground level.
BENCH MARK STAMPING: 1901 B 1983
MONUMENTATION: Survey Disk VM#: 3071
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Pier
The bench mark is at the seaward end of Avalon Pier, 137.7 feet (42.0 m) south
of a utility pole at the NE corner of the pier, 73.7 feet (22.5 m) north of the
NW corner of the abandoned Skipjack Restaurant, 68.8 feet (21.0 m) NE of a
piling at the corner where the pier meets the access road, 42.5 feet (13.0 m)
ESE of the end fence post for a 8.0-foot (2.4 m) high chain link fence on the
west side of the pier, 7.6 feet (2.3 m) NW of the westernmost of two small
cinderblock sheds on the north side of the restaurant, and at ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 01/22/1988
Station ID: 8571901 SUPERCEDED DATE: 04/21/2003
Name: AVALON, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12266 Latitude: 38° 42.7' N
USGS Quad: TILGHMAN Longitude: 76° 20.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1901 C 1983
MONUMENTATION: Survey Disk VM#: 3072
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Pier
The bench mark is on Avalon Pier, 134.7 feet (41.1 m) south of the south inside
corner where the pier meets the access road, 86.6 feet (26.4 m) SSW of the SE
corner of the porch on the south side of the abandoned Skipjack Restaurant, 73.9
feet (22.5 m) NNE of the SW corner of the pier, 15.3 feet (4.7 m) east of the
north end of a wood bulkhead which forms a part of the west face of the pier,
and at ground level.
BENCH MARK STAMPING: 1901 D 1983
MONUMENTATION: Survey Disk VM#: 3073
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set flush in the concrete apron at the north end of the
abandoned factory located south of Wharf Street at the waterfront, immediately
south of the east end of an east/west drainage channel in the concrete on the
east side of the factory in a covered open air section, 68.0 feet (20.7 m) SE of
the SE corner of a protective steel bar frame surrounding a large refrigeration
compressor, 40.9 feet (12.5 m) east of the east wall of the enclosed part of the
factory, and 5.4 feet (1.6 m) south of the fourth wood roof support beam south
of the NE corner of the factory.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 01/22/1988
Station ID: 8571901 SUPERCEDED DATE: 04/21/2003
Name: AVALON, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12266 Latitude: 38° 42.7' N
USGS Quad: TILGHMAN Longitude: 76° 20.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1901 E 1983
MONUMENTATION: Survey Disk VM#: 3074
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Pad
The bench mark is set flush in a 11.4-foot (3.5 m) diameter semi-circular
concrete pad inside the abandoned factory located south of Wharf Street at the
waterfront, 32.2 feet (9.8 m) west of an east wall of the factory, 26.8 feet
(8.2 m) east of the inside corner formed by one wing of the building, 7.4 feet
(2.3 m) north of an east/west wall which is a continuation of an exterior wall,
and 1.7 feet (0.5 m) from the edge of the semi-circular concrete structure where
the floor level drops 3.7 feet (1.2 m).
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 01/22/1988
Station ID: 8571901 SUPERCEDED DATE: 04/21/2003
Name: AVALON, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12266 Latitude: 38° 42.7' N
USGS Quad: TILGHMAN Longitude: 76° 20.1' W
T I D A L D A T U M S
Tidal datums at AVALON, CHESAPEAKE BAY based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: SEPT 29-NOV 28, 1983
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8574680 BALTIMORE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (10/23/1983) = 3.60
MEAN HIGHER HIGH WATER MHHW = 1.76
MEAN HIGH WATER MHW = 1.54
MEAN TIDE LEVEL MTL = 0.87
MEAN LOW WATER MLW = 0.21
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (10/29/1983) = -1.19
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
1901 A 1983 5.67 4.13
1901 B 1983 3.50 1.96
1901 C 1983 3.99 2.45
1901 D 1983 7.35 5.81
1901 E 1983 8.45 6.91
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 01/22/1988
Station ID: 8571901 SUPERCEDED DATE: 04/21/2003
Name: AVALON, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12266 Latitude: 38° 42.7' N
USGS Quad: TILGHMAN Longitude: 76° 20.1' 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.