U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
Station ID: 8570255 PUBLICATION DATE: 02/13/2004
Name: KEYDASH, ISLE OF WIGHT BAY
MD
NOAA Chart: 12211 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: OCEAN CITY Longitude: 75° 5.1' W ( -75.08500)
To reach the tidal bench marks from the intersection of Route 50 and
Philadelphia Avenue in Ocean City, proceed north on Philadelphia Avenue for 1.1
km (0.7 mi) to the intersection of Philadelphia Avenue and 9th Street, then turn
left and proceed east on 9th Street for 0.2 km (0.1 mi) to the intersection of
9th Street and Edgewater Avenue. The tide gage and staff were located on the
most southerly wooden pier on the western edge of the property at 901 Edgewater
Avenue, just north of 9th Street.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: C 104 RESET 1976
DESIGNATION: C 104 RESET
MONUMENTATION: Bench Mark disk VM#: 3020
AGENCY: National Ocean Survey (NOS) IDB PID#: HU1172
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 38° 20.7' N ( 38.34500) LONGITUDE: 74° 4.9' W ( -74.08170)
The bench mark is a disk set flush in the concrete foundation of the center
support for the water tower between 14th and 15 Streets and between St. Louis
and Philadelphia Avenues, 40.5 m (133 ft) west of the center of Philadelphia
Avene, 26.8 m (88 ft) west of powerline pole G1724-92352, 14.3 m (47 ft) east of
an alley, and 0.3 m (1 ft) west of the eastern corner of the foundation.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 8570255 PUBLICATION DATE: 02/13/2004
Name: KEYDASH, ISLE OF WIGHT BAY
MD
NOAA Chart: 12211 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: OCEAN CITY Longitude: 75° 5.1' W ( -75.08500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0255 C 1978
DESIGNATION: 857 0255 C
MONUMENTATION: Tidal Station disk VM#: 3016
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete pavement OPUS PID:
LATITUDE: 38° 20.5' N ( 38.34170) LONGITUDE: 75° 5.1' W ( -75.08500)
The bench mark is a disk set in concrete pavement on the east side of the Ocean
City Volunteer Fire Company Headquarters between the 1st and 2nd doors from the
north side of the building, 22 m (72 ft) south of 15th Street, 20.57 m (67.5 ft)
west of the centerline of Philadelphia Avenue, and 3.51 m (11.5 ft) north of the
centerline of the center door of Volunteer Fire Company Headquarters.
BENCH MARK STAMPING: 0255 D 1978
DESIGNATION: 857 0255 D
MONUMENTATION: Tidal Station disk VM#: 3017
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete porch OPUS PID#: BBDH85
LATITUDE: 38° 20.5' N ( 38.34170) LONGITUDE: 75° 5.1' W ( -75.08500)
The bench mark is a disk set in a concrete porch on the west side of pumping
station NO 2, on 15th Street, 24.87 m (81.6 ft) east of the centerline of St.
Louis Avenue, 13.41 m (44.0 ft) south of the centerline of 15th Street and 0.58
m (1.9 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 8570255 PUBLICATION DATE: 02/13/2004
Name: KEYDASH, ISLE OF WIGHT BAY
MD
NOAA Chart: 12211 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: OCEAN CITY Longitude: 75° 5.1' W ( -75.08500)
T I D A L D A T U M S
Tidal datums at KEYDASH, ISLE OF WIGHT BAY based on:
LENGTH OF SERIES: 1 YEAR
TIME PERIOD: June 1977 - May 1978
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8638610 SEWELLS POINT, HAMPTON ROADS
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (10/14/1977) = 1.113
MEAN HIGHER HIGH WATER MHHW = 0.558
MEAN HIGH WATER MHW = 0.505
MEAN SEA LEVEL MSL = 0.284
MEAN TIDE LEVEL MTL = 0.272
MEAN LOW WATER MLW = 0.040
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/11/1978) = -1.194
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
C 104 RESET 1976 2.471 1.966
0255 C 1978 1.903 1.398
0255 D 1978 2.429 1.924
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 8570255 PUBLICATION DATE: 02/13/2004
Name: KEYDASH, ISLE OF WIGHT BAY
MD
NOAA Chart: 12211 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: OCEAN CITY Longitude: 75° 5.1' W ( -75.08500)
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.