U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
In Dorchester County, MD from the intersection of US-50 and Route 16 in
Cambridge, MD, proceed south onto Route 16 (Cambridge Beltway) for 11.7 km (7.3
mi), turn left (south) onto Route 335 for 15.6 km (9.7 mi), turn left (east)
onto Route 336, continue straight (off Route 336) onto Phillips Gunning Club
Road for 1.6 km (1.0 mi) until the road dead ends at the Karen Noonan Center.
Bench mark network is located on Phillips Gunning Club Rd and on the Karen
Noonan Center property. Call before accessing property. The NWLON station is
located on the pier which is located on KNC property.
T I D A L B E N C H M A R K S
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: K 59 1942
DESIGNATION: K 59
MONUMENTATION: Tidal Station disk VM#: 17804
AGENCY: National Ocean Survey (NOS) IDB PID#: HV0483
SETTING CLASSIFICATION: Concrete kickblock OPUS PID:
LATITUDE: 38° 13.2' N ( 38.22081) LONGITUDE: 76° 2.3' W ( -76.03803)
The primary bench mark is a disk set flush in a concrete kickblock located in
the marsh edge, 19.43 m (63.8 ft) SSE from the SE corner of the bottom brick
step to the Karen Noonan Center on the south side of the center, 16.26 m (53.4
ft) NNE from the SW end of boat dock, and 0.47 m (1.5 ft) SE of witness post.
BENCH MARK STAMPING: 1421 A 2005
DESIGNATION: 857 1421 A
MONUMENTATION: Tidal Station disk VM#: 17800
AGENCY: National Ocean Service (NOS) IDB PID#: DH8202
SETTING CLASSIFICATION: Staging pad OPUS PID:
LATITUDE: 38° 13.3' N ( 38.22139) LONGITUDE: 76° 2.3' W ( -76.03811)
The primary bench mark is a disk set flush in the top of a concrete staging pad
located NNW from the Karen Noonan Center, 29.20 m (95.8 ft) NNW from the NE
corner of the Karen Noonan Center, 26.71 m (87.6 ft) west from the NW corner of
a white two story house, 0.65 m (2.1 ft) south from the NW corner of a 11 m
(36.1 ft) X 4 m (13.1 ft) concrete staging pad, and 0.16 m (0.5 ft) NE from the
SW edge of an 11 m (36.1 ft) X 4 m (13.1 ft) concrete staging pad.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BISHOP 3 AZI 1979
DESIGNATION: 857 1421 BISHOP3
MONUMENTATION: Survey disk VM#: 17801
AGENCY: Defense Mapping Agency IDB PID:
SETTING CLASSIFICATION: Concrete kick block OPUS PID:
LATITUDE: 38° 13.6' N ( 38.22719) LONGITUDE: 76° 2.8' W ( -76.04664)
The bench mark is a disk set in a concrete kickblock located in the marsh edge,
52.00 m (170.6 ft) WNW from a line of power poles on the SW side of Phillips
Gunning Club Road from pole number 512326, 40.20 m (131.9 ft) ESE from power
poles on the SW side of Phillips Gunning Road from pole number 512325, 9.50 m
(31.17 ft) south from centerline of Phillips Gunning Road, and 0.30 m (1.0 ft)
below road surface.
BENCH MARK STAMPING: TR130 2004
DESIGNATION: 857 1421 TR130
MONUMENTATION: Vertical Control disk VM#: 17802
AGENCY: Fish and Wildlife Service IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 38° 13.9' N ( 38.23170) LONGITUDE: 76° 2.3' W ( -76.03830)
The bench mark is a disk located at the marsh edge, 53.63 m (176.0 ft) NW from
power poles on the ENE side of Phillips Gunning Club Road pole number 512317,
21.92 m (71.9 ft) SE from the centerline of the intersection of Phillips Gunning
Road and the road leading to the communications tower, and 7.32 m (24.0 ft) SW
from the centerline of Phillips Gunning Club Road. The bench mark is set 0.2 m
(0.7 ft) below the road surface, crimped to a stainless steel rod driven to an
unspecified depth to refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: GRANGER 1998 NAWC-AD NAVAL AIR
TEST CENTER
DESIGNATION: 857 1421 GRANGER
MONUMENTATION: Aluminum marker VM#: 17803
AGENCY: NAWC-AD NAVAL AIR TEST CENTER IDB PID:
SETTING CLASSIFICATION: Concrete kickblock OPUS PID#: BBDG62
LATITUDE: 38° 13.3' N ( 38.22119) LONGITUDE: 76° 2.3' W ( -76.03769)
The bench mark is a disk set in a concrete kick block, 29.94 m (98.2 ft) east
from the ESE corner of the Karen Noonan Center, 21.76 m (71.4 ft) SE from the SE
corner of a two story white house at the Noonan Center, 8.14 m (26.7 ft) west
from the centerline of Phillips Gunning Club Road, and 6.92 m (22.7 ft) ESE from
a well pump head located between the Noonan Center and a two story white house.
BENCH MARK STAMPING: 1421 B 2012
DESIGNATION: 857 1421 B
MONUMENTATION: Metal Rod VM#: 20461
AGENCY: CO-OPS IDB PID:
SETTING CLASSIFICATION: Steel rod OPUS PID:
LATITUDE: 38° 13.5' N ( 38.22510) LONGITUDE: 76° 2.4' W ( -76.03975)
The bench mark is a deep rod surrounded by a concrete kick block set in the
marsh on the north side of the dirt road leading to the Karen Noonan Center,
11.80m (38.75 ft) northeast of a power pole on the southwest side of the dirt
road leading to Karen Noonan Center, 6.01m (19.7 ft) north of a power pole on
the northeast side of the dirt road, 0.85m (2.8 ft) southwest of an orange
witness post driven into the ground, surrounded by a 0.33m (13 in) diameter
concrete kick block, driven 39.0m (128.1 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1421 C 2012
DESIGNATION: 857 1421 C
MONUMENTATION: Metal Rod VM#: 20462
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Steel rod OPUS PID:
LATITUDE: 38° 13.8' N ( 38.22953) LONGITUDE: 76° 3.1' W ( -76.05214)
The bench mark is 14.30 m (47.0 ft) ENE of the power pole #512/320 on the south
side of the dirt road leading to the Karen Noonan Center, 6.70m (22.0 ft) NE of
the centerline of the dirt road, 0.82m (2.7 ft) SSW of an orange witness post
driven into the ground, is surrounded by a 0.48m (19 in) diameter concrete kick
block, 0.38m (15 in) above the marsh, driven 13.0m (42.7 ft) to refusal.
BENCH MARK STAMPING: 1421 D 2013
DESIGNATION: 857 1421 D
MONUMENTATION: Metal Rod VM#: 20790
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 38° 13.4' N ( 38.22283) LONGITUDE: 76° 2.3' W ( -76.03839)
The bench mark is 38.39 m (126.0 ft) southeast of a power pole, 26.42 m (86.7
ft) west of the north side of the Karen Noonan sign, 10.52 m (34.5 ft)
south-southwest of the centerline of the dirt road leading into the Karen Noonan
center, and 3.11 m (10.2 ft) east of a NOAA witness post, being a stainless
steel rod driven 16.1 m (52.8 ft) to refusal with a grease sleeve and NOAA logo
cap, 15.32 cm (6 inches) above ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1421 E 2016
DESIGNATION: 857 1421 E
MONUMENTATION: Flange-encased Rod VM#: 21963
AGENCY: CO-OPS IDB PID:
SETTING CLASSIFICATION: Steel rod OPUS PID:
LATITUDE: 38° 13.6' N ( 38.22625) LONGITUDE: 76° 2.6' W ( -76.04306)
The bench mark is a stainless steel rod, 55.30 m (181.4 ft) east of a power pole
numbered 512 Choptank 328, 6.80 m (22.3 ft) north of the centerline of a dirt
road leading to the Karen Noonan Center, 2.50 m (8.2 ft) NE of a National
Wildlife Refuge sign, and 0.32 m (1.0 ft) south of an orange witness post driven
into the ground, surrounded by a 13 inch (33 cm) diameter concrete kick block,
driven to refusal, 37.0 ft (11.3 m).
BENCH MARK STAMPING: 1421 F 2017
DESIGNATION: 857 1421 F
MONUMENTATION: Metal Rod VM#: 22416
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 38° 13.7' N ( 38.22783) LONGITUDE: 76° 2.9' W ( -76.04842)
The bench mark is a flange-encased stainless steel deep rod located 76.2 m
(250.0 ft) north of power pole 512 the eleventh power pole north of the Karen
Noonan Center, 3.8 m (12.5 ft) east of the center of the road, 1 m (3.3 ft) west
of an orange witness post, driven to a depth of 13.8 m (45.2 ft), and encased in
a PVC pipe with raised kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
T I D A L D A T U M S
Tidal datums at BISHOPS HEAD, HOOPERS STRAIT based on:
LENGTH OF SERIES: 11 YEARS
TIME PERIOD: 9/05-8/09, 4/10-3/12, 5/14-4/19
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8571892 CAMBRIDGE, CHOPTANK RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (10/12/2019) = 1.420
MEAN HIGHER HIGH WATER MHHW = 0.629
MEAN HIGH WATER MHW = 0.580
North American Vertical Datum NAVD88 = 0.370
MEAN SEA LEVEL MSL = 0.311
MEAN TIDE LEVEL MTL = 0.311
MEAN LOW WATER MLW = 0.042
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (03/03/2018) = -0.658
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
K 59 1942 0.833 0.253
1421 A 2005 1.175 0.595
BISHOP 3 AZI 1979 0.794 0.214
TR130 2004 0.747 0.167
GRANGER 1998 NAWC-AD NAVAL AIR TEST
CENTER 0.876 0.296
1421 B 2012 0.925 0.345
1421 C 2012 1.056 0.476
1421 D 2013 0.836 0.256
1421 E 2016 0.762 0.182
1421 F 2017 0.925 0.345
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 8
Station ID: 8571421 PUBLICATION DATE: 10/20/2020
Name: BISHOPS HEAD, HOOPERS STRAIT
MD
NOAA Chart: 12261 Latitude: 38° 13.2' N ( 38.22039)
USGS Quad: BLOODSWORTH ISLAND Longitude: 76° 2.3' W ( -76.03867)
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.