Bench Mark Sheet for 8571117, Ewell, Smith Island MD

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 8571117                         PUBLICATION DATE:  03/18/2011
Name:       EWELL, SMITH ISLAND                               
            MD
NOAA Chart: 12261                           Latitude:   37° 59.7' N (  37.99500)
USGS Quad:  EWELL                           Longitude:  76°  1.9' W ( -76.03170)


To reach the tidal bench marks from the city dock in Crisfield, proceed by
charter boat (Captain Jason) west to Smith Island and Ewell at the north end of
the island.  The bench marks are located in the vicinity of the Bayside Inn, the
Methodist Church, and Caleb Jones Road.  The tide gauge was located at the dock
NW of the Bayside Inn.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  NO 2 1997
                         DESIGNATION:          857 1117 TIDAL 2

MONUMENTATION:           Survey disk                           VM#:        13882
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:        
SETTING CLASSIFICATION:  Aluminum alloy rod                    OPUS PID#: BBBZ40
LATITUDE:   37° 59.8' N (  37.99608)          LONGITUDE:  76°  2.0' W ( -76.03300)


The primary bench mark is a disk located near the county dock, 5.81 m (19.1 ft)
NW of the W corner of a refreshment stand, 5.24 m (17.2 ft) W of the N corner of
a refreshment stand, 3.45 m (11.3 ft) NE of the end of the county dock, 0.90 m
(3.0 ft) SW of the end of a wooden boardwalk, and 0.55 m (1.8 ft) SE of a
witness post. The bench mark is set 21 cm (0.7 ft) below ground level, crimped
to the top of an aluminum rod driven 12.8 m (42.0 ft), and encased in a 4-inch
PVC pipe and concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8571117                         PUBLICATION DATE:  03/18/2011
Name:       EWELL, SMITH ISLAND                               
            MD
NOAA Chart: 12261                           Latitude:   37° 59.7' N (  37.99500)
USGS Quad:  EWELL                           Longitude:  76°  1.9' W ( -76.03170)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:   
                         DESIGNATION:          857 1117 USE 1
                         ALIAS:                NO STAMPING 1

MONUMENTATION:           Survey disk                           VM#:        13881
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:        
SETTING CLASSIFICATION:  Concrete sidewalk                     OPUS PID:        
LATITUDE:   37° 59.7' N (  37.99500)          LONGITUDE:  76°  1.9' W ( -76.03170)


The primary bench mark is a disk set in a concrete sidewalk on the NW side of
the front entrance to the Methodist Church on Caleb Jones Road in Ewell, about
15 m (50 ft) east of the intersection of Caleb Jones Road and Smith Island Road.



                         BENCH MARK STAMPING:  NO 3 1997
                         DESIGNATION:          857 1117 TIDAL 3

MONUMENTATION:           Survey disk                           VM#:        13883
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:        
SETTING CLASSIFICATION:  Aluminum alloy rod                    OPUS PID#: BBDN51
LATITUDE:   37° 59.7' N (  37.99567)          LONGITUDE:  76°  2.0' W ( -76.03289)


The bench mark is a disk located just east of the Smith Island Town Center,
25.42 m (83.4 ft) SW of the SE corner of the Bayside Inn, 22.20 m (72.8 ft) SE
of the SE corner of the Bayside Gift Shop, 4.72 m (15.5 ft) north of the SE
property corner of the Bayside Inn, and 0.52 m (1.7 ft) NE of a USACE witness
post. The bench mark is 12 cm (0.4 ft) below ground level, crimped to the top of
an aluminum rod driven 11.9 m (39.0 ft), and encased in a 4-inch PVC pipe and
concrete kickblock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8571117                         PUBLICATION DATE:  03/18/2011
Name:       EWELL, SMITH ISLAND                               
            MD
NOAA Chart: 12261                           Latitude:   37° 59.7' N (  37.99500)
USGS Quad:  EWELL                           Longitude:  76°  1.9' W ( -76.03170)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  NO 4 1997
                         DESIGNATION:          857 1117 TIDAL 4

MONUMENTATION:           Survey disk                           VM#:        13884
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:        
SETTING CLASSIFICATION:  Aluminum alloy rod                    OPUS PID#: BBDN62
LATITUDE:   37° 59.7' N (  37.99503)          LONGITUDE:  76°  1.9' W ( -76.03233)


The bench mark is a disk, located near the ball field, 12.80 m (42.0 ft) SE of
the centerline of Campground Road, 11.35 m (37.2 ft) SW of the centerline of
Somers Road, 3.52 m (11.5 ft) S of the SW corner of a small wooden building, and
0.34 m (1.1 ft) west of a USACE witness post at the west side of a baseball
field backstop. The bench mark is 12 cm (0.4 ft) below ground level, crimped to
the top of an aluminum rod driven 12.8 m (42 ft), and encased in a 4-inch PVC
pipe and concrete kickblock.



                         BENCH MARK STAMPING:  NO 5 1997
                         DESIGNATION:          857 1117 TIDAL 5

MONUMENTATION:           Survey disk                           VM#:        13885
AGENCY:                  US Army Corps of Engineers (USE)      IDB PID#:        
SETTING CLASSIFICATION:  Concrete step                         OPUS PID:        
LATITUDE:   37° 59.7' N (  37.99578)          LONGITUDE:  76°  1.9' W ( -76.03214)


The bench mark is an aluminum survey disk set flush in the concrete step in
front of the Verizon Telephone building at 20884 Caleb Jones Road, 7.25 m (23.8
ft) NE of the SE corner of a concrete walk, 4.27 m (14.0 ft) SE of the NW corner
of the building, and 2.87 m (9.4 ft) WNW of the east corner of the building.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8571117                         PUBLICATION DATE:  03/18/2011
Name:       EWELL, SMITH ISLAND                               
            MD
NOAA Chart: 12261                           Latitude:   37° 59.7' N (  37.99500)
USGS Quad:  EWELL                           Longitude:  76°  1.9' W ( -76.03170)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  1117 A 2010
                         DESIGNATION:          857 1117 A

MONUMENTATION:           Survey disk                           VM#:        19713
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  in concrete                           OPUS PID:        
LATITUDE:   37° 59.7' N (  37.99517)          LONGITUDE:  76°  2.0' W ( -76.03331)


The bench mark is disk set flush in a concrete sidewalk located on the NE side
of the front entrance to the United Methodist Church on Caleb Jones Road, 13.10
m (43.0 ft) south of SW corner of the Town Center Building, 7.12 m (23.4 ft) SSW
of the centerline of Caleb Jones Road, 2.10 m (6.9 ft) NW of the NE corner of
the church, and 0.42 m (1.4 ft) NNE of the north wall of the church.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8571117                         PUBLICATION DATE:  03/18/2011
Name:       EWELL, SMITH ISLAND                               
            MD
NOAA Chart: 12261                           Latitude:   37° 59.7' N (  37.99500)
USGS Quad:  EWELL                           Longitude:  76°  1.9' W ( -76.03170)


                            T I D A L   D A T U M S 


Tidal datums at EWELL, SMITH ISLAND based on:

     LENGTH OF SERIES:      4 MONTHS
     TIME PERIOD:           July 2010 - October 2010
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8635750 LEWISETTA, POTOMAC RIVER


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     MEAN HIGHER HIGH WATER                     MHHW   =  0.563
     MEAN HIGH WATER                            MHW    =  0.510
     MEAN SEA LEVEL                             MSL    =  0.286
     MEAN TIDE LEVEL                            MTL    =  0.278
     MEAN LOW WATER                             MLW    =  0.046
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     NO 2 1997                                   0.982    0.472
     857 1117 USE 1                              1.216    0.706
     NO 3 1997                                   0.809    0.299
     NO 4 1997                                   0.868    0.358
     NO 5 1997                                   1.772    1.262
     1117 A 2010                                 1.224    0.714


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8571117                         PUBLICATION DATE:  03/18/2011
Name:       EWELL, SMITH ISLAND                               
            MD
NOAA Chart: 12261                           Latitude:   37° 59.7' N (  37.99500)
USGS Quad:  EWELL                           Longitude:  76°  1.9' W ( -76.03170)


                             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.

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