U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
This station was installed in support of a project with the U.S. Army Corp of
Engineers (USACE). Due to the special nature of this project, the bench marks
are described in terms specific to the project.To reach the tidal bench marks
from Lowes Wharf in Sherwood, MD, proceed west by boat for 4.3 km (2.7 miles) to
the personnel pier at Poplar Island. The bench marks are located along the
islands perimeter road and cross dikes. The tide gauge is located at the SE end
of the personnel pier T-section.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: USACE CM3 2004
DESIGNATION: CM-3 TRUE
MONUMENTATION: Bench Mark disk VM#: 19749
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: Aluminum rod driven to the ground OPUS PID:
LATITUDE: 38° 45.5' N ( 38.75833) LONGITUDE: 76° 22.5' W ( -76.37500)
The primary bench mark is a disk at the NE corner of cell 4D, 15.68 m (51.4 ft)
east of the east corner of the Murden Memorial monument stone, 10.62 m (34.8 ft)
WSW of the west corner of the landing craft ramp, and 1.02 m (3.3 ft) NNW of a
wooden bollard. The bench mark is set 15 cm (0.5 ft) below ground, crimped to an
aluminum rod driven to an unknown depth to substantial resistance, and encased
in a 5-inch logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NONE
DESIGNATION: SP-6
MONUMENTATION: Pipe Cap VM#: 19750
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: Driven to the ground OPUS PID:
LATITUDE: 38° 45.5' N ( 38.75833) LONGITUDE: 76° 22.5' W ( -76.37500)
The bench mark is a 2-inch capped pipe at the NE corner of cell 3A, 12.20 m
(40.0 ft) ENE of the SE sluice gate operator for spillway #6, 5.55 m (18.2 ft)
SE of the SE railing of the gangway for spillway #6, and 3.47 m (11.4 ft) SW of
the centerline of the perimeter road. The bench mark is set 30 cm (1.0 ft) below
the road grade, driven to an unknown depth to substantial resistance, and
encased in a 12-inch steel casing.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: USACE CM1 2004
DESIGNATION: CM-1
MONUMENTATION: Bench Mark disk VM#: 19751
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: Aluminum rod driven to the ground OPUS PID:
LATITUDE: 38° 45.5' N ( 38.75833) LONGITUDE: 76° 22.5' W ( -76.37500)
The bench mark is a disk at the NE corner of cell 3C, 9.99 m (32.8 ft) ESE of
the south sluice gate operator for spillway #5, 4.55 m (14.9 ft) south of the
south railing of the gangway for spillway #5, and 5.03 m (16.5 ft) west of the
centerline of the perimeter road. The bench mark is set 15 cm (0.5 ft) below
ground, crimped to an aluminum rod driven to an unknown depth to substantial
resistance, and encased in a 5-inch logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NONE
DESIGNATION: SP-8
MONUMENTATION: Pipe Cap VM#: 19752
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: Driven to the ground OPUS PID:
LATITUDE: 38° 45.5' N ( 38.75833) LONGITUDE: 76° 22.5' W ( -76.37500)
The bench mark is a 2-inch capped pipe at the approximate midpoint of the cross
dike, 3.66 m (12.0 ft) NE of the centerline of the cell 1A-3D cross dike, 0.93 m
(3.1 ft) SE of the northernmost of two wooden bollards, and 0.91 m (3.0 ft) NNE
of the other wooden bollard. The bench mark is set 9 cm (0.3 ft) below ground,
driven to an unknown depth to substantial resistance, and encased in a 12-inch
steel casing.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: PIP 1 2002
DESIGNATION: PIP-1
MONUMENTATION: Bench Mark disk VM#: 19753
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: Aluminum rod driven to the ground OPUS PID:
LATITUDE: 38° 45.5' N ( 38.75833) LONGITUDE: 76° 22.5' W ( -76.37500)
The bench mark is a disk at the south edge of cell 3A, 20.12 m (66.0 ft) NNE of
the NE corner of a metal shed, 7.94 m (26.0 ft) NW of the center of an abandoned
electric box, and 3.93 m (12.9 ft) ENE of the island's well. The bench mark is
set 6 cm (0.2 ft) below ground, crimped to an aluminum rod driven to an unknown
depth to substantial resistance, and encased in a 4-inch PVC pipe with concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
T I D A L D A T U M S
Tidal datums at POPLAR ISLAND based on:
LENGTH OF SERIES: 3 YEARS
TIME PERIOD: March 2007 - February 2010
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8575512 U.S. NAVAL ACADEMY, SEVERN R., CHES. BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (12/26/2009) = 1.081
MEAN HIGHER HIGH WATER MHHW = 0.469
MEAN HIGH WATER MHW = 0.402
MEAN SEA LEVEL MSL = 0.236
MEAN TIDE LEVEL MTL = 0.233
MEAN LOW WATER MLW = 0.065
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/03/2008) = -0.830
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
USACE CM3 2004 1.508 1.106
NONE 2.042 1.640
USACE CM1 2004 2.064 1.662
NONE 2.215 1.813
PIP 1 2002 2.773 2.371
Foot Notes:
Bench mark PIP 1 2002 is based on one differential leveling connection and does
not meet the quality control standards of the NOS. Therefore, caution should be
used when deriving elevations for this mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8572271 PUBLICATION DATE: 03/09/2012
Name: POPLAR ISLAND
MD
NOAA Chart: 12270 Latitude: 38° 45.5' N ( 38.75833)
USGS Quad: CLAIRBORNE Longitude: 76° 22.5' W ( -76.37500)
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.