U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 04/05/1990
Station ID: 8573364 SUPERCEDED DATE: 04/21/2003
Name: TOLCHESTER BEACH, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12278 Latitude: 39° 12.8' N
USGS Quad: ROCK HALL Longitude: 76° 14.7' W
To reach the tidal bench marks from the intersection of State Highways 213 and
291 in Chestertown, proceed west on State Highway 291 for 0.5 mile (0.8 km) to
State Highway 20, turn right on State Highway 20 and go 7.0 miles (11.3 km) to
State Highway 21, turn right on State Highway 21 and go 3.3 miles (5.3 km) to
Tolchester Marina at the end of the highway. The bench marks are on the marina
property and along State Highway 21. The tide gage and staff are on the
bulkhead along the entrance channel to the marina.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
MONUMENTATION: VM#: 3159
AGENCY: PID:
SETTING CLASSIFICATION:
BENCH MARK STAMPING: KNOB 1950
MONUMENTATION: Survey Disk VM#: 3157
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in the top of a 1.0-foot (0.3 m) square concrete
monument on top of a prominent hill between the marina and the bay, 18.0 feet
(5.5 m) NW of a spanish oak tree, 14.0 feet (4.3 m) SE of a post oak tree, and
1.0 foot (0.3 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 04/05/1990
Station ID: 8573364 SUPERCEDED DATE: 04/21/2003
Name: TOLCHESTER BEACH, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12278 Latitude: 39° 12.8' N
USGS Quad: ROCK HALL Longitude: 76° 14.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 6 1971
MONUMENTATION: Survey Disk VM#: 3158
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in the top of a concrete monument on the SW side of
the prominent hill between the marina and the bay, 198.0 feet (60.4 m) north of
the bulkhead running along the north side of the entrance channel, 67.1 feet
(20.5 m) NW of the center of three fuel tank vent pipes at the north edge of a
parking lot, 39.7 feet (12.1 m) north of a basketball goal post, and 0.8 foot
(0.2 m) south of an orange witness post.
BENCH MARK STAMPING: 3364 B 1983
MONUMENTATION: Survey Disk VM#: 3160
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is on the east side of the tennis courts, 104.5 feet (31.9 m)
north of the NW corner of a wooden bulkhead, 71.4 feet (21.8 m) SSW of the
easternmost wood fence post along the north edge of the marina property, 61.0
feet (18.6 m) NE of the SE corner of the fence around the tennis courts, and
14.9 feet (4.5 m) east of the fence around the tennis court (in line with the
nets). The bench mark is 0.4 feet (0.1 m) above ground level, crimped to a
stainless steel rod driven 60 feet (18 m) to refusal, and encased in a 4-inch
PVC pipe with a protective cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 04/05/1990
Station ID: 8573364 SUPERCEDED DATE: 04/21/2003
Name: TOLCHESTER BEACH, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12278 Latitude: 39° 12.8' N
USGS Quad: ROCK HALL Longitude: 76° 14.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3364 C 1983
MONUMENTATION: Survey Disk VM#: 3161
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is on an earthen dam on the north side of State Highway 21,
across from the main gate to Tolchester Marina, 104.4 feet (31.8 m) SE of a
fence post by the pond, 80.7 feet (24.6 m) north of the east gate post at the
entrance to the marina, 72.8 feet (22.2 m) NNE of the west gate post at the
entrance to the marina, 43.8 feet (13.4 m) NE of the centerline of State Highway
21, 18.9 feet (5.8 m) south of the pond shore, and 0.2 foot (0.1 m) south of an
orange witness post. The bench mark is 0.4 foot (0.1 m) below ground level,
crimped to a stainless steel rod driven 54 feet (16 m) to refusal, and encased
in a 4-inch PVC pipe with a protective cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 04/05/1990
Station ID: 8573364 SUPERCEDED DATE: 04/21/2003
Name: TOLCHESTER BEACH, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12278 Latitude: 39° 12.8' N
USGS Quad: ROCK HALL Longitude: 76° 14.7' W
T I D A L D A T U M S
Tidal datums at TOLCHESTER BEACH, CHESAPEAKE BAY based on:
LENGTH OF SERIES: 12 MONTHS
TIME PERIOD: JULY 1986-JUNE 1987
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 (03/19/1983) = 4.05
MEAN HIGHER HIGH WATER (MHHW) = 1.74
MEAN HIGH WATER (MHW) = 1.42
MEAN TIDE LEVEL (MTL) = 0.83
MEAN LOW WATER (MLW) = 0.23
MEAN LOWER LOW WATER (MLLW) = 0.00
LOWEST OBSERVED WATER LEVEL (02/09/1987) = -2.15
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
0 0.00 0.00
KNOB 1950 27.92 26.50
NO 6 1971 7.02 5.60
3364 B 1983 6.65 5.23
3364 C 1983 10.91 9.49
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 04/05/1990
Station ID: 8573364 SUPERCEDED DATE: 04/21/2003
Name: TOLCHESTER BEACH, CHESAPEAKE BAY
MARYLAND
NOAA Chart: 12278 Latitude: 39° 12.8' N
USGS Quad: ROCK HALL Longitude: 76° 14.7' 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.