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Datums Page Page 1 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
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 2.4 km (1.5 mi) to Fort
Avenue. Turn right and travel east on Fort Avenue for 2.9 km (1.8 mi) 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
DESIGNATION: 857 4680 TIDAL 32
MONUMENTATION: Tidal Station disk VM#: 434
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0586
SETTING CLASSIFICATION: Granite sill OPUS PID:
LATITUDE: 39° 16.0' N ( 39.26653) LONGITUDE: 76° 34.9' W ( -76.58086)
The primary bench mark is a disk set in the top of a granite sill on the west
side of the U.S. Naval Reserve Center Building at Fort McHenry, 19.81 m (65.0
ft) north of the SW corner of the building, 10.10 m (33.1 ft) SE of the
centerline of Halsey Road, and 0.43 m (1.4 ft) above the sidewalk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 27 1922
DESIGNATION: 857 4680 TIDAL 27
MONUMENTATION: Tidal Station disk VM#: 429
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0579
SETTING CLASSIFICATION: Granite foundation OPUS PID:
LATITUDE: 39° 15.8' N ( 39.26306) LONGITUDE: 76° 34.7' W ( -76.57917)
The bench mark is a disk set in the center of an octagon shaped granite cannon
base at the easternmost point of the star shaped fort on the Fort McHenry
grounds, 45.7 m (150 ft) ESE of the fort flagpole, 1.68 m (5.5 ft) ESE of a pile
of cannon balls, and 0.12 m (0.4 ft) east of the west edge of the base.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 28 1922
DESIGNATION: TIDAL 28 STA 72
MONUMENTATION: Tidal Station disk VM#: 430
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0580
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 39° 15.8' N ( 39.26392) LONGITUDE: 76° 34.7' W ( -76.57769)
The bench mark is a disk set in the east corner of the 1.01 m x 1.01 m (3.0 ft x
3.0 ft) concrete sub-base on the east leg of a range beacon near the east end of
the Fort McHenry grounds, 16.40 m (53.8 ft) south of the SW leg of an electric
meter box, 12.71 m (41.7 ft) WNW of the offshore edge of the seawall, 0.3 m (1
ft) east of the east leg of the beacon, and 0.3 m (1 ft) below ground. Note:
Contact the Chief Ranger at Fort McHenry prior to leveling and recovering marks.
BENCH MARK STAMPING: 29 1922
DESIGNATION: 857 4680 TIDAL 29
MONUMENTATION: Tidal Station disk VM#: 431
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0582
SETTING CLASSIFICATION: Granite sea wall OPUS PID:
LATITUDE: 39° 16.0' N ( 39.26606) LONGITUDE: 76° 34.7' W ( -76.57875)
The bench mark is a disk set in the granite seawall coping at Fort McHenry,
16.80 m (55.1 ft) north of the Fire Department Barracks, 6.10 m (20.0 ft) east
of the centerline of the Fire Department Pier, and 0.30 m (1.0 ft) south of the
north edge of the sea wall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 30 1922
DESIGNATION: 857 4680 TIDAL 30
MONUMENTATION: Tidal Station disk VM#: 432
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0584
SETTING CLASSIFICATION: Granite doorsill OPUS PID:
LATITUDE: 39° 16.0' N ( 39.26606) LONGITUDE: 76° 34.8' W ( -76.57922)
The bench mark is a disk set in the top of a granite door sill in the COE
compound at Fort McHenry, 6.10 m (20.0 ft) west of the centerline of a paved
road between the Fire Barracks and Soil Laboratory, 2.01 m (6.6 ft) south of the
NE corner of the building, and 1.01 m (3.0 ft) above ground.
BENCH MARK STAMPING: 31 1922
DESIGNATION: 857 4680 TIDAL 31
MONUMENTATION: Tidal Station disk VM#: 433
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0585
SETTING CLASSIFICATION: Granite doorsill OPUS PID:
LATITUDE: 39° 16.0' N ( 39.26703) LONGITUDE: 76° 34.8' W ( -76.58058)
The bench mark is a disk set in the granite door sill on the SW side of the Fort
McHenry U.S. Naval Reserve Boiler Room (Building 4), 13.60 m (44.6 ft) north of
the NW corner of the main U.S. Naval Reserve Building, 6.70 m (22.0 ft) NW of
the south corner of the building, 5.50 m (18.0 ft) NNE of the road centerline,
1.40 m (4.6 ft) NW of the edge of the top step, and 1.01 m (3.3 ft) above
ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 35 1922
DESIGNATION: TIDAL 35 STA 72
MONUMENTATION: Tidal Station disk VM#: 435
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0576
SETTING CLASSIFICATION: Granite doorsill OPUS PID:
LATITUDE: 39° 15.9' N ( 39.26522) LONGITUDE: 76° 35.0' W ( -76.58397)
The bench mark is a disk 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, 38.7 m (127 ft) SSW of the centerline of Fort Avenue, 11.52 m
(37.8 ft) WNW of the brick wall around the Fort McHenry grounds, and 0.15 m (0.5
ft) 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 6 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: 857 4680 TIDAL BASIC
ALIAS: BASIC
MONUMENTATION: Bench Mark disk VM#: 437
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0578
SETTING CLASSIFICATION: Concrete monument OPUS PID#: JV0578
LATITUDE: 39° 15.8' N ( 39.26414) LONGITUDE: 76° 34.9' W ( -76.58108)
The bench mark is a disk 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 Fort McHenry grounds, 89 m (292 ft) east of the east face of the bottom step
of the memorial, 78.64 m (258.0 ft) WSW of the SW corner of the visitors center,
and 0.61 m (2.0 ft) 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 7 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: FORT MCHENRY 1982
DESIGNATION: FORT MCHENRY
MONUMENTATION: Survey disk VM#: 3952
AGENCY: US Army Corps of Engineers (USE) IDB PID#:
SETTING CLASSIFICATION: Aluminum alloy rod OPUS PID:
LATITUDE: 39° 16.0' N ( 39.26631) LONGITUDE: 76° 34.9' W ( -76.58108)
The bench mark is a disk, located in the front yard of the Office Building at
the U.S. Army Corps of Engineers Fort McHenry, 11.84 m (38.8 ft) NNE of the NE
face of the building, 10.75 m (35.3 ft) south of the back side of the center
pole of the sign: U.S. Army Corps of Engineers, Baltimore District, Fort
McHenry Yard, and 7.07 m (23.2 ft) ENE of power pole No. 816425. The bench mark
is crimped to the top of an aluminum rod driven an unspecified depth, and
encased in a 4-inch PVC pipe.
BENCH MARK STAMPING: 4680 B 1997
DESIGNATION: 857 4680 B
MONUMENTATION: Flange-encased Rod VM#: 3953
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: DI3808
LATITUDE: 39° 16.0' N ( 39.26619) LONGITUDE: 76° 34.8' W ( -76.57944)
The bench mark is a flange encased rod located in the lawn on the north side of
the U.S. Army Corps of Engineers Fort McHenry, 27.77 m (91.1 ft) SE of power
pole number 816425 on the east side of the parking lot, 24.58 m (80.6 ft) SW of
the sea wall, and 4.78 m (15.7 ft) NNE of the NE face of the office building.
The datum point is set 0.12 M (0.4 ft) below ground, being the top of a
stainless steel rod driven 12.20 m (40 ft) to refusal, and encased in a 5-inch
NGS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4680 C 1997
DESIGNATION: 857 4680 C
MONUMENTATION: Flange-encased Rod VM#: 13778
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 39° 16.0' N ( 39.26600) LONGITUDE: 76° 34.9' W ( -76.58094)
The bench mark is a flange encased rod located in the lawn on the SW side of the
Naval Reserve Readiness Center just west of the U.S. Army Corps of Engineers
Fort McHenry Yard, 12.51 m (41.0 ft) NW of the NW edge of a parking lot, 11.09 M
(36.38 ft) NW of the (center of the) north edge of a concrete pad supporting an
anchor, 8.23 m (27.0 ft) SW of a large flag pole surrounded by a hedge, and 3.38
m (11.1 ft) NW of the north edge of a concrete pad supporting an anchor. The
datum point is set 0.11 m (0.36 ft) below ground, being the top of a stainless
steel rod driven 4.60 m (15.1 ft) to refusal, and encased in a 5-inch NGS logo
cap.
BENCH MARK STAMPING:
DESIGNATION: 857 4680 TIDAL 1=SEAWALL
MONUMENTATION: Chiseled Cross VM#: 13779
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JV0581
SETTING CLASSIFICATION: Granite sea wall OPUS PID:
LATITUDE: 39° 15.9' N ( 39.26564) LONGITUDE: 76° 34.7' W ( -76.57806)
The bench mark is a chiseled cross on the coping stone of the granite seawall,
located in the center of three drill holes at the first angle in the seawall SE
of the Baltimore Fire Department pier, 45.95 m (150.8 ft) SE of the SE side of
the pier, 0.87 m (2.9 ft) from the SE corner of the seawall, 0.70 m (2.3 ft)
from the NE corner of the seawall, and 0.67 m (2.2 ft) from the outside angle of
the seawall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 9 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
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: January 1983 - December 2001
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION:
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (09/19/2003) = 2.484
MEAN HIGHER HIGH WATER MHHW = 0.506
MEAN HIGH WATER MHW = 0.415
North American Vertical Datum NAVD88 = 0.254
MEAN SEA LEVEL MSL = 0.244
MEAN TIDE LEVEL MTL = 0.241
MEAN LOW WATER MLW = 0.067
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/24/1908) = -1.556
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
32 1922 1.907 1.492
27 1922 9.413 8.998
28 1922 2.108 1.693
29 1922 1.399 0.984
30 1922 2.810 2.395
31 1922 1.890 1.475
35 1922 8.276 7.861
857 4680 TIDAL BASIC 9.519 9.104
FORT MCHENRY 1982 1.677 1.262
4680 B 1997 1.648 1.233
4680 C 1997 1.895 1.480
857 4680 TIDAL 1=SEAWALL 1.363 0.948
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 10 of 10
Station ID: 8574680 PUBLICATION DATE: 10/06/2011
Name: BALTIMORE, FORT MCHENRY, PATAPSCO RIVER
MD
NOAA Chart: 12281 Latitude: 39° 16.0' N ( 39.26667)
USGS Quad: BALTIMORE EAST Longitude: 76° 34.7' W ( -76.57833)
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.