U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
PUBLICATION DATE: 03/28/1988
Station ID: 8574680 SUPERCEDED DATE: 04/21/2003
Name: BALTIMORE (FORT MCHENRY), PATAPSCO RIVER
MARYLAND
NOAA Chart: 12281 Latitude: 39° 16.0' N
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W
To reach the tidal bench marks from the north bound Baltimore-Washington
Expressway (State Highway 295) take the Water View exit east to State Highway 2
(Hanover Street), proceed north on Hanover Street for 1.5 miles (2.4 km) to Fort
Avenue, turn right and travel east on Fort Avenue for 1.8 miles (2.9 km) to the
entrance of Fort McHenry, turn left onto Wallace Avenue, then right again onto
Nimitz Drive and then left onto Halsey Road to its end, turn right and continue
past a gate to the U.S. Corps of Engineers (COE) compound. The bench marks are
located in the U.S. Naval Reserve compound, the COE compound, and on the Fort
McHenry grounds. The tide gage and staff are located on the COE pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 32 1922
MONUMENTATION: Survey Disk VM#: 434
AGENCY: PID#: JV0586
SETTING CLASSIFICATION: Granite Sill
The bench mark is set in the top of a granite door sill on the west side of the
U.S. Naval Reserve Center Building, 65.1 feet (19.8 m) NE of the SW corner of
the building, 33.0 feet (10.1 m) SE of the centerline of Halsey Road, and 1.4
feet (0.4 m) above the sidewalk.
BENCH MARK STAMPING: 25 1919
MONUMENTATION: Survey Disk VM#: 427
AGENCY: PID#: JV0583
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in the top of a concrete monument in the COE compound,
46.3 feet (14.1 m) east of the NE corner of the COE soil laboratory (a single
story structure with yellow siding), 38 feet (12 m) south of the edge of the sea
wall, and 0.5 foot (0.2 m) above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
PUBLICATION DATE: 03/28/1988
Station ID: 8574680 SUPERCEDED DATE: 04/21/2003
Name: BALTIMORE (FORT MCHENRY), PATAPSCO RIVER
MARYLAND
NOAA Chart: 12281 Latitude: 39° 16.0' N
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 27 1922
MONUMENTATION: Survey Disk VM#: 429
AGENCY: PID#: JV0579
SETTING CLASSIFICATION: Granite Foundation
The bench mark is set in the center of an octagon shaped granite cannon base at
the easternmost point of the star shaped fort at Fort McHenry grounds, 150 feet
(46 m) ESE of the fort flagpole, 5.5 feet (1.7 m) ESE of a pile of cannon balls,
and 0.4 foot (0.1 m) east of the west edge of the base.
BENCH MARK STAMPING: 28 1922
MONUMENTATION: Survey Disk VM#: 430
AGENCY: PID#: JV0580
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set in the east corner of the 3-foot (1 m) square concrete
sub-base on the east leg of a range beacon near the east end of the Fort McHenry
grounds, 53.7 feet (16.4 m) south of the SW leg of an electric meter box, 41.8
feet (12.7 m) WNW of the offshore edge of the sea wall, 1.1 feet (0.3 m) east of
the east leg of the beacon, and 0.4 foot (0.1 m) below the ground.
BENCH MARK STAMPING: 29 1922
MONUMENTATION: Survey Disk VM#: 431
AGENCY: PID#: JV0582
SETTING CLASSIFICATION: Granite Sea Wall
The bench mark is set in the sea wall cap in the COE compound, 61.3 feet (18.7
m) NE of the doorway of Building 2609, 26.6 feet (8.1 m) SE of the centerline of
the fire boat pier, and 1 foot (0.3 m) south of the north edge of the sea wall
cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
PUBLICATION DATE: 03/28/1988
Station ID: 8574680 SUPERCEDED DATE: 04/21/2003
Name: BALTIMORE (FORT MCHENRY), PATAPSCO RIVER
MARYLAND
NOAA Chart: 12281 Latitude: 39° 16.0' N
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 30 1922
MONUMENTATION: Survey Disk VM#: 432
AGENCY: PID#: JV0584
SETTING CLASSIFICATION: Granite Sill
The bench mark is set in the top of a granite sill in the COE compound, 20 feet
(6 m) west of the centerline of a paved road between the fire department
barracks and soil laboratory, 6.7 feet (2.0 m) south of the NE corner of a
warehouse, and 3 feet (1 m) above the ground.
BENCH MARK STAMPING: 31 1922
MONUMENTATION: Survey Disk VM#: 433
AGENCY: PID#: JV0585
SETTING CLASSIFICATION: Granite Sill
The bench mark is set in the top of a granite door sill of the U.S. Naval
Reserve Center boiler room at the north end of Halsey Road, 44.7 feet (13.6 m)
north of the NW corner of the main Naval Reserve Center Building, 18.0 feet (5.5
m) NNE of the centerline of the entrance road to the COE compound, 4.6 feet (1.4
m) NW of the edge of the top step, and 3 feet (1 m) above the ground.
BENCH MARK STAMPING: 35 1922
MONUMENTATION: Survey Disk VM#: 435
AGENCY: PID#: JV0576
SETTING CLASSIFICATION: Granite Sill
The bench mark is set in the main entrance door sill to the Southern States Coop
Mills office building at the intersection of East Fort Avenue and Wallace
Street, 127 feet (39 m) SSW of the centerline of Fort Avenue, 37.8 feet (11.5 m)
WNW of the brick wall around the Fort McHenry grounds, and 0.5 foot (0.2 m) SE
of the west side of the entrance way to the building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
PUBLICATION DATE: 03/28/1988
Station ID: 8574680 SUPERCEDED DATE: 04/21/2003
Name: BALTIMORE (FORT MCHENRY), PATAPSCO RIVER
MARYLAND
NOAA Chart: 12281 Latitude: 39° 16.0' N
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4680 A 1980
MONUMENTATION: Survey Disk VM#: 436
AGENCY: PID:
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is located in the COE compound in line with a line of maple
trees, 122.9 feet (37.5 m) NNW of a flagpole, 90.6 feet (27.6 m) north of the NW
corner of the office building, and 42.1 feet (12.8 m) SW of a power pole at the
end of the pier. The bench mark is 0.1 foot (0.03 m) below the ground, crimped
to a galvanized steel rod driven 37 feet (11 m) to refusal.
BENCH MARK STAMPING: NO STAMPING 1
MONUMENTATION: Survey Disk VM#: 437
AGENCY: PID#: JV0578
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in the top of a concrete monument in the grassy area
between the Francis Scott Key memorial statue and the visitors center on the For
McHenry grounds, 292.0 feet (89.0 m) east of the east face of the bottom step of
the memorial, 258.0 feet (78.6 m) WSW of the SW corner of the visitors center,
and 2.0 feet (0.6 m) above the ground. The monument bears the inscription
UNITED STATES COAST AND GEODETIC SURVEY BASIC BENCH MARK.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
PUBLICATION DATE: 03/28/1988
Station ID: 8574680 SUPERCEDED DATE: 04/21/2003
Name: BALTIMORE (FORT MCHENRY), PATAPSCO RIVER
MARYLAND
NOAA Chart: 12281 Latitude: 39° 16.0' N
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W
T I D A L D A T U M S
Tidal datums at BALTIMORE (FORT MCHENRY), PATAPSCO RIVER based on:
LENGTH OF SERIES: 19 YEARS
TIME PERIOD: 1960-1978
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION:
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (08/23/1933) = 7.90
MEAN HIGHER HIGH WATER (MHHW) = 1.66
MEAN HIGH WATER (MHW) = 1.35
MEAN TIDE LEVEL (MTL) = 0.80
* NATIONAL GEODETIC VERTICAL DATUM-1929 (NGVD) = 0.28
MEAN LOW WATER (MLW) = 0.24
MEAN LOWER LOW WATER (MLLW) = 0.00
BALTIMORE CITY DATUM (BCD) = -0.57
LOWEST OBSERVED WATER LEVEL (01/24/1908) = -4.90
* NGVD reference based on adjustment of 1972 AND NOS levels of 1984.
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
32 1922 6.49 5.14
25 1919 6.16 4.81
27 1922 31.11 29.76
28 1922 7.14 5.79
29 1922 4.83 3.48
30 1922 9.46 8.11
31 1922 6.44 5.09
35 1922 27.39 26.04
4680 A 1980 5.37 4.02
NO STAMPING 1 31.47 30.12
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
PUBLICATION DATE: 03/28/1988
Station ID: 8574680 SUPERCEDED DATE: 04/21/2003
Name: BALTIMORE (FORT MCHENRY), PATAPSCO RIVER
MARYLAND
NOAA Chart: 12281 Latitude: 39° 16.0' N
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' 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.