U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
To reach the tidal benchmarks from the intersection of MD-12 (Snow Hill Road)
and HWY-13, follow HWY-13 south towards the town of Snow Hill for 14.9 miles
(23.98 KM). After crossing the Pocomoke River, make the first right onto River
St. Follow River St. for 0.25 miles (0.40 KM) to the James T. Sturgis memorial
pavilion. The gauge is located at the SW section of the dock and the bench
marks are located throughout the town.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 21 BALTO
DESIGNATION: 21 BALTO
MONUMENTATION: Tidal Station disk VM#: 17832
AGENCY: US Coast and Goedetic Survey
(USC&GS) IDB PID#: HU0236
SETTING CLASSIFICATION: Stone porch OPUS PID:
LATITUDE: 38° 10.6' N ( 38.17680) LONGITUDE: 75° 23.6' W ( -75.39310)
The bench mark is a disk set into a stone porch located at the Worcester County
Courthouse, 11.93 m (39.14 ft) south of the centerline of curb S edge of market
street, and 10.43 m (34.22 ft) east of NW corner of court house, 3.06 m (10.03
ft) north of the centerline of main doors, northwest side of a stone porch, and
0.44 m (1.44 ft) above the sidewalk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1359 A 2005
DESIGNATION: 857 1359 A
MONUMENTATION: Tidal Station disk VM#: 17833
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete pad OPUS PID:
LATITUDE: 38° 10.7' N ( 38.17830) LONGITUDE: 75° 23.6' W ( -75.39330)
The bench mark is set in a concrete pad in front ot the Snow Hill Post Office on
Washington Street, 4.51 m (14.8 ft) NW of the centerline of the PO entrance
doors, 3.99 m (13.1 ft) NE of the NE curb of Washington Street,0.52 m (1.7 ft)
SE of the mailbox, and 0.45 m (1.5 ft) SW of the SW face of the building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: SNOW HILL 1935
DESIGNATION: SNOW HILL
MONUMENTATION: Tidal Station disk VM#: 17838
AGENCY: US Coast and Goedetic Survey
(USC&GS) IDB PID#: HU0237
SETTING CLASSIFICATION: Bridge control house OPUS PID:
LATITUDE: 38° 10.6' N ( 38.17690) LONGITUDE: 75° 23.6' W ( -75.39360)
The bench mark is a disk set vertically in the SW side of the bridge control
house, 6.87m (22.53 ft) centerline of light pole NE corner of draw span of the
bridge, 6.79 m (22.27 ft) NE of the centerline of Washington Street, 0.28 m (.92
ft) NW of the south corner of the control house, and 0.63 m (2.06 ft) above the
sidewalk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: SNOW HILL 2002
DESIGNATION: SNOW HILL RM 1
MONUMENTATION: Horizontal Station disk VM#: 17839
AGENCY: US Corp of Engineers (USE) IDB PID#:
SETTING CLASSIFICATION: Seawall foundation OPUS PID:
LATITUDE: 38° 10.7' N ( 38.17806) LONGITUDE: 75° 23.8' W ( -75.39603)
The bench mark is a disk located in the middle of the James T. Sturgis Memorial
Park, near the pavilion, 30.98 m (101.6 ft) W of the center of flag pole, 1.19
m (3.9 ft) from the waters edge of the dock and 1.03 m (3.37 ft) NW of the NW
corner of the concrete pavillion pad, .17 m (.55 ft) S of the N face of concrete
retaining wall along N edge of the park.
BENCH MARK STAMPING: 1359 B 2005
DESIGNATION: 857 1359 B
MONUMENTATION: Tidal Station disk VM#: 17840
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Pavillion foundation OPUS PID:
LATITUDE: 38° 10.7' N ( 38.17790) LONGITUDE: 75° 23.8' W ( -75.39650)
The benchmark is a disk located in the south corner of the concrete pad in the
James T. Sturgis memorial Park. The benchmark is 30.5 m (100.06 ft) NW of
centerline of River St., 10.75 m (35.26 ft) SEof NW corner of concrete pavillion
retaining wall, .13 m (.42 ft) SS eastern edge of the concrete pavillion pad.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: WIN 1961
DESIGNATION: WIN
MONUMENTATION: Survey disk VM#: 18682
AGENCY: Maryland Bureau of Control Survey IDB PID#: HU2710
SETTING CLASSIFICATION: Bridge sidewalk OPUS PID:
LATITUDE: 38° 10.8' N ( 38.17931) LONGITUDE: 75° 23.7' W ( -75.39461)
The bench mark is set flush with the sidewalk in the NW side of the bridge
control house, 8.54 m (28.0 ft) west of centerline of light pole at the north
corner of the draw span, 5.75 m (18.86 ft) from centerline of Washington st, and
4.73 m (15.52) NW edge of side walk.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
T I D A L D A T U M S
Tidal datums at SNOW HILL, POCOMOKE RIVER based on:
LENGTH OF SERIES: 4 YEARS
TIME PERIOD: September 2005 - August 2009
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 (05/12/2008) = 1.035
MEAN HIGHER HIGH WATER MHHW = 0.584
MEAN HIGH WATER MHW = 0.550
North American Vertical Datum NAVD88 = 0.357
MEAN SEA LEVEL MSL = 0.328
MEAN TIDE LEVEL MTL = 0.301
MEAN LOW WATER MLW = 0.052
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/03/2008) = -0.581
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
21 BALTO 6.225 5.675
1359 A 2005 2.389 1.839
SNOW HILL 1935 2.886 2.336
SNOW HILL 2002 1.934 1.384
1359 B 2005 2.096 1.546
WIN 1961 2.256 1.706
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8571359 PUBLICATION DATE: 11/29/2011
Name: SNOW HILL, POCOMOKE RIVER
MD
NOAA Chart: 12211 Latitude: 38° 10.7' N ( 38.17833)
USGS Quad: SNOW HILL Longitude: 75° 23.8' W ( -75.39667)
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.