U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
To reach the tidal bench marks on Barren Island (which is approximately 35 km
(22 mi) SW of Cambridge and about a 10-minute boat ride from the fishing creek
at a small boat dock at Tyler Cove) from the boat dock near Honga, go WSW by
boat following a narrow channel until the bay waters are entered. Continue
westerly until the last bouy light, then make a wide turn south (sunken
obstructions near Barren Island) for approximately 1.3 km (0.8 mi) passing the
NW corner of the island. Continue 0.3 km (0.2 mi) south along the west side of
the island, then turn east and proceed with caution to the island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1579 B 2001
DESIGNATION: 857 1579 B TIDAL
MONUMENTATION: Flange-encased Rod VM#: 16625
AGENCY: National Ocean Service (NOS) IDB PID#: AJ8224
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 38° 20.4' N ( 38.34000) LONGITUDE: 76° 15.8' W ( -76.26330)
The primary bench mark is a flange encased rod located on Barren Island north
along the beach on the west side of the island, 0.08 km (0.05 mi) east of bench
mark 1579 C 2001, 13.56 m (44.5 ft) east of the center of a Y junction, 3.26 m
(10.7 ft) NE of the centerline of a truck trail, and 0.9 m (2.9 ft) WSW of a
fiberglass carsonite witness post. The datum point is set 1 cm (0.03 ft) above
ground, being the top of a stainless steel rod driven 53.6 M (176 ft) to
refusal, in a sleeve extending to a depth of 1.2 m (3.9 ft), and encased in a
5-inch logo cap. Note: The sleeve depth does not meet the specifications for a
Class A mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1579 A 2001
DESIGNATION: 857 1579 A TIDAL
MONUMENTATION: Flange-encased Rod VM#: 16624
AGENCY: National Ocean Service (NOS) IDB PID#: AJ8223
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 38° 20.5' N ( 38.34170) LONGITUDE: 76° 15.9' W ( -76.26500)
The bench mark is a flange encased rod located on the NW corner of Barren Island
where the east-west wooden sea wall turns SE, 0.2 km (0.1 mi) NW of bench mark
1579 B 2001, 0.2 km (0.1 mi) westerly of bench mark 33B1 1, 29.57 m (97 ft) SW
where the joint for the east-west and SE sea walls meet, 17.07 m (56.0 ft) south
of the north edge of Barren Island which edge is south of a wooden sea wall,
3.05 m (10.0 ft) south of the centerline inside curve in a truck trail
(abandoned runway), and 0.76 m (2.5 ft) north of a carsonite witness post. The
datum point is set 7 cm (0.2 ft) above ground, being the top of a stainless
steel rod driven 30.5 m (100.1 ft) to refusal, in a sleeve extending to a depth
of 1.2 m (3.9 ft), and encased in a 5-inch logo cap. Note: The sleeve depth
does not meet the specifications for a Class A mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1579 C 2001
DESIGNATION: 857 1579 C TIDAL
MONUMENTATION: Flange-encased Rod VM#: 16626
AGENCY: National Ocean Service (NOS) IDB PID#: AJ8225
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 38° 20.4' N ( 38.34000) LONGITUDE: 76° 15.8' W ( -76.26330)
The bench mark is a flange encased rod located on Barren Island north along the
beach on the west side of the island, 0.13 km (0.08 mi) west of bench mark 1579
B 2001, 0.08 km (0.05 mi) easterly of bench mark 33B1 3, 8.87 m (29.1 ft) NW of
the centerline of the truck trail, 8.60 m (28.2 ft) east of a lone pine tree,
and 0.64 m (2.1 ft) SE of a fiberglass carsonite witness post. The datum point
is set 2 cm (0.07 ft) above ground, being the top of a stainless steel rod
driven 24.4 m (80.1 ft) to refusal, in a sleeve extending to a depth of 1.2 m
(3.9 ft), and encased in a 5-inch logo cap. Note: The sleeve depth does not
meet the specifications for a Class A mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1579 D 2001
DESIGNATION: 857 1579 D TIDAL
MONUMENTATION: Flange-encased Rod VM#: 16627
AGENCY: National Ocean Service (NOS) IDB PID#: AJ8226
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 38° 20.4' N ( 38.34000) LONGITUDE: 76° 15.8' W ( -76.26330)
The bench mark is a flange encased rod located on Barren Island north along the
beach on the west side of the island, 0.2 km (0.1 mi) north of bench mark 33B1
2, 0.2 km (0.1 mi) SE of bench mark 33B1 3, 12.41 m (40.7 ft) south of a pine
tree at the edge of the tree line, and 0.52 m (1.7 ft) WSW of a fiberglass
carsonite witness post. The datum point is set 9 cm (0.3 ft) above ground,
being the top of a stainless steel rod driven 24.2 m (79.4 ft) to refusal, in a
sleeve extending to a depth of 1.2 m (3.9 ft), and encased in a 5-inch logo cap.
Note: The sleeve depth does not meet the specifications for a Class A mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1579 E 2001
DESIGNATION: 857 1579 E TIDAL
MONUMENTATION: Flange-encased Rod VM#: 16628
AGENCY: National Ocean Service (NOS) IDB PID#: AJ8227
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID:
LATITUDE: 38° 20.3' N ( 38.33830) LONGITUDE: 76° 15.7' W ( -76.26170)
The bench mark is a flange encased rod located on Barren Island southeasterly
along the west bank to the mark on the left in a sandy area, between the beach
and marsh land, 0.2 km (0.1 mi) north of bench mark 33B1 1, 0.2 km (0.1 mi) SE
of bench mark 1579 D 2001, 4.33 m (14.2 ft) NW of a small PVC pipe, and 0.76 m
(2.5 ft) SW of a fiberglass carsonite witness post. The datum point is set 20
cm (0.7 ft) above ground, being the top of a flange encased rod driven 30.5 m
(100.1 ft) to refusal, in a sleeve extending to a depth of 1.2 m (3.9 ft), and
encased in a 5-inch logo cap. Note: The sleeve depth does not meet the
specifications for a Class A mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BARREN 3 1993
DESIGNATION: BARREN 3
MONUMENTATION: Survey disk VM#: 16629
AGENCY: US Army Corps Of Engineers (USE) IDB PID#: AJ8228
SETTING CLASSIFICATION: Concrete Post OPUS PID:
LATITUDE: 38° 20.6' N ( 38.34330) LONGITUDE: 76° 15.8' W ( -76.26330)
The bench mark is a disk set in a prefabricated concrete post located near the
NE corner of Barren Island, 0.3 km (0.2 mi) east along the beach from bench mark
857 1579 A TIDAL, 20.42 m (67.0 ft) SW of a sign bearing the words "CRAB LINE",
16.46 m (54.0 ft) SE of the edge of the beach, 0.52 m (1.7 ft) north of a
fiberglass carsonite witness post, and 0.17 m (0.6 ft) above ground.
BENCH MARK STAMPING:
DESIGNATION: 33B1 1
MONUMENTATION: See descriptive text VM#: 16630
AGENCY: US Army Corps Of Engineers (USE) IDB PID#: AJ8230
SETTING CLASSIFICATION: Steel rebar with yellow cap OPUS PID:
LATITUDE: 38° 20.2' N ( 38.33670) LONGITUDE: 76° 15.7' W ( -76.26170)
The bench mark is an unknown length of steel rebar with a yellow cap located
along the south edge of the west bank of Barren Island, just north of where the
island splits due to a slough, 0.6 km (0.4 mi) south of bench mark 33B1 3, 0.3
km (0.2 mi) SE from bench mark 33B1 2, 0.2 km (0.1 mi) south of bench mark 1579
E 2001, 1.55 m (5.1 ft) west of a fiberglass carsonite witness post, and 0.70 m
(2.3 ft) west of a fiberglass carsonite witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: 33B1 2
MONUMENTATION: See descriptive text VM#: 16631
AGENCY: US Army Corps Of Engineers (USE) IDB PID#: AJ8229
SETTING CLASSIFICATION: Steel rebar with yellow cap OPUS PID:
LATITUDE: 38° 20.3' N ( 38.33830) LONGITUDE: 76° 15.8' W ( -76.26330)
The bench mark is an unknown length of steel rebar with a yellow cap located on
Barren Island near the boat landing area, 0.16 km (0.1 mi) south of bench mark
857 1579 D TIDAL, 0.16 km (0.1 mi) NW of bench mark 857 1579 E TIDAL, 14.08 m
(46.2 ft) NE of the west edge of the bank, 0.73 m (2.4 ft) WSW of a fiberglass
carsonite witness post, 0.70 m (2.3 ft) NE of a fiberglass carsonite witness
post, and 0.11 m (0.4 ft) above ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
T I D A L D A T U M S
Tidal datums at BARREN ISLAND, CHESAPEAKE BAY based on:
LENGTH OF SERIES: 15 MONTHS
TIME PERIOD: January 2002 - March 2003
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8577330 SOLOMONS ISLAND, PATUXENT RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (03/21/2003) = 0.952
MEAN HIGHER HIGH WATER MHHW = 0.472
MEAN HIGH WATER MHW = 0.420
North American Vertical Datum NAVD88 = 0.370
MEAN SEA LEVEL MSL = 0.240
MEAN TIDE LEVEL MTL = 0.234
MEAN LOW WATER MLW = 0.047
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/24/2003) = -0.592
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1579 B 2001 1.166 0.746
1579 A 2001 1.163 0.743
1579 C 2001 0.934 0.514
1579 D 2001 1.069 0.649
1579 E 2001 1.060 0.640
BARREN 3 1993 0.933 0.513
33B1 1 0.887 0.467
33B1 2 0.874 0.454
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 9 of 9
Station ID: 8571579 PUBLICATION DATE: 01/27/2005
Name: BARREN ISLAND, CHESAPEAKE BAY
MD
NOAA Chart: 12261 Latitude: 38° 20.5' N ( 38.34170)
USGS Quad: BARREN ISLAND Longitude: 76° 15.9' W ( -76.26500)
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.