U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8573927 PUBLICATION DATE: 10/13/2020
Name: CHESAPEAKE CITY
MD
NOAA Chart: 12277 Latitude: 39° 31.6' N ( 39.52670)
USGS Quad: ELKTON Longitude: 75° 48.6' W ( -75.81000)
To reach the tidal bench marks from the south end of the State Highway 213
bridge over the Chesapeake and Delaware (C & D) Canal at Chesapeake City,
proceed south on State Highway 213 for 0.89 km (0.55 mi) and take the South
Chesapeake City exit, continue 0.3 km (0.2 mi) NNE (towards canal) from the base
of the exit to a signpost directing the way to the C & D Canal Museum, turn
right and follow the curving road for 0.2 km (0.1 mi) to a T-intersection, turn
right and follow the curving road for 0.6 km (0.4 mi) to a T-intersection, turn
left and proceed 0.08 km (0.05 mi) to the main gate of the U.S. Army Corps of
Engineers (COE) facility and the C & D Canal Museum. The bench marks are located
on the COE grounds. The tide gage is located at the west corner of the bulkhead
at the west end of the COE grounds.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 3927 B 1982
DESIGNATION: 857 3927 B
MONUMENTATION: Tidal Station disk VM#: 3173
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Galvanized steel rod OPUS PID:
LATITUDE: 39° 31.6' N ( 39.52653) LONGITUDE: 75° 48.4' W ( -75.80706)
The primary bench mark is a disk crimped to a galvanized steel rod located SE of
the COE administration building, 34.59 m (113.5 ft) SW of the centerline of the
main road, 10.58 m (34.7 ft) NNE of the center of the southernmost section of a
dock on the north shore of the harbor, 4.48 m (14.7 ft) SE of the concrete
walkway leading to the dock, 0.61 m (2.0 ft) east of the easternmost pole
supporting electrical boxes, and 0.33 m (1.1 ft) below ground. The rod is driven
7.0m (24 ft) to refusal and encased in a 4-inch pvc-pipe with cap and concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8573927 PUBLICATION DATE: 10/13/2020
Name: CHESAPEAKE CITY
MD
NOAA Chart: 12277 Latitude: 39° 31.6' N ( 39.52670)
USGS Quad: ELKTON Longitude: 75° 48.6' W ( -75.81000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: U 2 1931 6.834
DESIGNATION: U 2
MONUMENTATION: Bench Mark disk VM#: 3167
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JU1833
SETTING CLASSIFICATION: Concrete monument OPUS PID#: JU1833
LATITUDE: 39° 31.6' N ( 39.52717) LONGITUDE: 75° 48.4' W ( -75.80728)
The bench mark is a disk set in a 0.24 m (0.8 ft) square concrete monument
located south of the COE administration building, 14.57 m (47.8 ft) south of the
west concrete wall for the steps leading to the basement of the administration
building, 10.27m (33.7 ft) North of the centerline of the main road, 8.56m (28.1
ft) West of the West edge of a sidewalk leading to the administrative building,
and 0.15m (0.5 ft) above the ground.
BENCH MARK STAMPING: 3927 D 2006
DESIGNATION: 857 3927 D
MONUMENTATION: Flange-encased Rod VM#: 18224
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: BBCZ38
LATITUDE: 39° 31.6' N ( 39.52683) LONGITUDE: 75° 48.5' W ( -75.80794)
The bench mark is a stainless steel rod located 57.45 m (188.48 ft) south of the
south most corner of a small white 8.5' x 7.5' building, 14.6 m (47.9 ft) east
of the NE corner of a 4' x 4' concrete pad that has a trnasformer mounted on it.
The datum point is the top of a stainless steel rod driven 4.753 m (15.594 ft)
to refusal, inside a sleeve extending to the depth of 0.9 m (3.0 ft) and encased
in a 5-inch NOS logo cap with a concrete kickblock, mounted with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8573927 PUBLICATION DATE: 10/13/2020
Name: CHESAPEAKE CITY
MD
NOAA Chart: 12277 Latitude: 39° 31.6' N ( 39.52670)
USGS Quad: ELKTON Longitude: 75° 48.6' W ( -75.81000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3927 E 2015
DESIGNATION: 857 3927 E
MONUMENTATION: Flange-encased Rod VM#: 21637
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 39° 31.6' N ( 39.52747) LONGITUDE: 75° 48.6' W ( -75.81000)
The bench mark is a stainless steel rod located on the west side of the COE
facility near the NOAA tide station enclosure, 13.5 m (44.3 ft) northwest of the
northwest corner of the COE maintenance shop, 12.3 m (40.4 ft) east of the inner
bulkhead joint on the northern reach of the seawall, and 4.1 m (13.5 ft) south
of the southeast corner of the meteorological mast. The mark is driven 12.2 m
(40.0 ft) to refusal, and encased in a 5-inch (13 cm) NOS logo cap, mounted 8 cm
(3 inches) below grade.
BENCH MARK STAMPING: 3927 F 2016
DESIGNATION: 857 3927 F
MONUMENTATION: Tidal Station disk VM#: 21909
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Retaining wall OPUS PID:
LATITUDE: 39° 31.5' N ( 39.52503) LONGITUDE: 75° 48.4' W ( -75.80661)
The bench mark is a brass disk with NOS stamping set flush on the concrete
surface of the bridge abutment on the NE ledge, 7.9 m (26.0 ft) SW of the
telephone pole NO 41296 35396 #17, 4.42 m (14.5 ft) SE of the centerline of
route 286, and 0.24 m (0.8 ft) NW of the SE ledge of the bridge abutment.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8573927 PUBLICATION DATE: 10/13/2020
Name: CHESAPEAKE CITY
MD
NOAA Chart: 12277 Latitude: 39° 31.6' N ( 39.52670)
USGS Quad: ELKTON Longitude: 75° 48.6' W ( -75.81000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3927 G 2016
DESIGNATION: 857 3927 G
MONUMENTATION: Flange-encased Rod VM#: 21910
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 39° 31.6' N ( 39.52736) LONGITUDE: 75° 48.3' W ( -75.80547)
The bench mark is a stainless steel rod set on the hill South of the lower canal
road, 26.2 m (86.0 ft) East of the SE corner of the West storm sewer cover along
the South side of the lower canal road, 9.9 m (32.5 ft) South of the centerline
for the lower canal road, and 3.0 m (10.1 ft) North of an orange NOAA witness
post, driven 12.5 m (41.0 ft) to refusal, encased in an NOS access cover, and
receded 7.6 cm below grade.
BENCH MARK STAMPING: 95-91 1991
DESIGNATION: 95-91 1991
MONUMENTATION: Survey disk VM#: 21911
AGENCY: USACE IDB PID:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 39° 31.7' N ( 39.52817) LONGITUDE: 75° 48.0' W ( -75.80083)
The bench mark is a USACE brass disk set in a concrete monument along the S side
of the Lower Canal road located 21.3 m (70.0 ft) SE of pole #740, 10.2 m (33.4
ft) W of the center of a catch basin, and 5.5 m (18.0 ft) S of the centerline
of the Lower Canal road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8573927 PUBLICATION DATE: 10/13/2020
Name: CHESAPEAKE CITY
MD
NOAA Chart: 12277 Latitude: 39° 31.6' N ( 39.52670)
USGS Quad: ELKTON Longitude: 75° 48.6' W ( -75.81000)
T I D A L D A T U M S
Tidal datums at CHESAPEAKE CITY based on:
LENGTH OF SERIES: 15 YEARS
TIME PERIOD: 5/81-4/83, 4/04-3/12, 1/13-12/17
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8551910 REEDY POINT, C&D CANAL
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (09/19/2003) = 2.639
MEAN HIGHER HIGH WATER MHHW = 0.983
MEAN HIGH WATER MHW = 0.921
MEAN TIDE LEVEL MTL = 0.493
North American Vertical Datum NAVD88 = 0.487
MEAN SEA LEVEL MSL = 0.474
MEAN LOW WATER MLW = 0.065
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (04/05/1975) = -1.138
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
3927 B 1982 1.193 0.272
U 2 1931 6.834 2.197 1.276
3927 D 2006 2.617 1.696
3927 E 2015 1.856 0.935
3927 F 2016 2.611 1.690
3927 G 2016 3.559 2.638
95-91 1991 2.807 1.886
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8573927 PUBLICATION DATE: 10/13/2020
Name: CHESAPEAKE CITY
MD
NOAA Chart: 12277 Latitude: 39° 31.6' N ( 39.52670)
USGS Quad: ELKTON Longitude: 75° 48.6' W ( -75.81000)
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.