U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 10/29/1985
Station ID: 8551973 SUPERCEDED DATE: 04/21/2003
Name: ST. GEORGES, C&D CANAL
DELAWARE
NOAA Chart: 12277 Latitude: 39° 33.3' N
USGS Quad: ST. GEORGES Longitude: 75° 38.9' W
To reach the tidal bench marks from Elkton, MD, proceed east on U.S. Highway 40
for 6.2 miles (10.0 km) to State Highway 72, proceed south on State Highway 72
for 3.7 miles (6.0 km) to U.S. Highway 13, then south on U.S. Highway 13 for 1.4
miles (2.3 km) to a point just before the St. Georges bridge at the C&D canal,
bear right and follow the road under the bridge to the center of town. Proceed
to Delaware Street, turn right onto Delaware Street and drive to a small bridge,
turn right just before the bridge onto a dirt road and drive to its end, turn
left onto the canal access road and drive to the pier. The bench marks are
located in the area between Main Street and the pier. The tide gage and staff
were located on the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1973
MONUMENTATION: Survey Disk VM#: 2984
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Wall
The bench mark is set flush in the south concrete bridge wall (engraved 1922) of
the small bridge on Delaware Street in St. Georges, 25.7 feet (7.8 m) west of
the east end of the wall, 25.1 feet (7.7 m) south of the north bridge wall
(engraved 309), 10.4 feet (3.2 m) east of the west end of the wall, and 3.0 feet
(0.9 m) above the roadway.
BENCH MARK STAMPING: NO 2 1973
MONUMENTATION: Survey Disk VM#: 2985
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set flush in a concrete storm drain on the north side of
Delaware Street, where the road curb takes a jog for the drain, 99.5 feet (30.3
m) WNW of the center of the intersection of Delaware Street and Broad Street,
and 38.1 feet (11.6 m) north of the south curb of Delaware Street.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 10/29/1985
Station ID: 8551973 SUPERCEDED DATE: 04/21/2003
Name: ST. GEORGES, C&D CANAL
DELAWARE
NOAA Chart: 12277 Latitude: 39° 33.3' N
USGS Quad: ST. GEORGES Longitude: 75° 38.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1973
MONUMENTATION: Survey Disk VM#: 2986
AGENCY: PID:
SETTING CLASSIFICATION: Sidewalk
The bench mark is set flush in the SE corner of a raised sidewalk in front of
the M&K Studio on the west side of Main Street, in line with the south edge of
the sidewalk on the south side of Delaware Street, 45.9 feet (14.0 m) WNW of the
NW corner of the small grocery store at the SE corner of the intersection of
North Main Street and Delaware Street, 43.1 feet (13.1 m) south of the north
edge of the raised sidewalk, and 5.8 feet (1.8 m) east of the front of the M&K
Studio.
BENCH MARK STAMPING: NO 4 1973
MONUMENTATION: Survey Disk VM#: 2987
AGENCY: PID:
SETTING CLASSIFICATION: Mat Foundation
The bench mark is set flush in the bottom step of the stairway encircling the
eastern of the twelfth pair of bridge supports as counted from the canal, and
the eastern of the eighth pair of bridge supports as counted from where the road
becomes a bridge.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 10/29/1985
Station ID: 8551973 SUPERCEDED DATE: 04/21/2003
Name: ST. GEORGES, C&D CANAL
DELAWARE
NOAA Chart: 12277 Latitude: 39° 33.3' N
USGS Quad: ST. GEORGES Longitude: 75° 38.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1973 A 1979
MONUMENTATION: Survey Disk VM#: 2988
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is at the top of the canal embankment, 55.9 feet (17.0 m) north
of utility pole #280, 45.0 feet (13.7 m) north of the lower dirt road, 20.2 feet
(6.2 m) south of the centerline of the dirt road on top of the embankment, and
1.9 feet (0.6 m) north of a witness post. The bench mark is crimped to a
stainless steel rod driven 30 feet (9 m) to refusal, encased in a PVC pipe and
concrete kickblock, and 0.3 foot (0.1 m) above ground level.
BENCH MARK STAMPING: 30/71
MONUMENTATION: Survey Disk VM#: 2989
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Post
The bench mark is 295.0 feet (89.9 m) east of Bench Mark 1973 A 1979, 49.5 feet
(15.1 m) north of the centerline of the dirt road along the canal, 21.0 feet
(6.4 m) south of the centerline of the upper dirt road, and 12.7 feet (3.9 m)
north of a utility pole with a cable running to the canal. The bench mark is
set flush in a concrete post 0.3 foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 10/29/1985
Station ID: 8551973 SUPERCEDED DATE: 04/21/2003
Name: ST. GEORGES, C&D CANAL
DELAWARE
NOAA Chart: 12277 Latitude: 39° 33.3' N
USGS Quad: ST. GEORGES Longitude: 75° 38.9' W
T I D A L D A T U M S
Tidal datums at ST. GEORGES, C&D CANAL based on:
LENGTH OF SERIES: 9 MONTHS
TIME PERIOD: AUGUST 1973 - MAY 1974
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8557380 LEWES
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (12/02/1974) = 7.75
MEAN HIGHER HIGH WATER MHHW = 4.81
MEAN HIGH WATER MHW = 4.59
MEAN TIDE LEVEL MTL = 2.39
MEAN LOW WATER MLW = 0.18
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (01/17/1975) = -2.46
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1973 10.61 6.02
NO 2 1973 18.46 13.87
NO 3 1973 20.61 16.02
NO 4 1973 28.00 23.41
1973 A 1979 17.02 12.43
30/71 18.29 13.70
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 10/29/1985
Station ID: 8551973 SUPERCEDED DATE: 04/21/2003
Name: ST. GEORGES, C&D CANAL
DELAWARE
NOAA Chart: 12277 Latitude: 39° 33.3' N
USGS Quad: ST. GEORGES Longitude: 75° 38.9' 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.