Superseded Bench Mark Sheet for 8630249, CHINCOTEAGUE, USCG STATION VA

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  4

                                                   PUBLICATION DATE:  01/11/1982
Station ID: 8630249                                SUPERCEDED DATE:   04/21/2003
Name:       U.S.C.G STATION, CHINCOTEAGUE ISLAND              
            VIRGINIA
NOAA Chart: 12211                                  Latitude:         37° 55.9' N
USGS Quad:  CHINCOTEAGUE WEST                      Longitude:        75° 23.0' W


To reach the tidal bench marks from the junction of State Highway 175 and Main
Street in Chincoteague, proceed 0.3 mile southwest along Main Street, to the
U.S. Coast Guard Base.  The tide gage and staff were located at the northern
edge of the U.S. Coast Guard south wharf at Chincoteague.


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


                 PRIMARY BENCH MARK STAMPING:  NO 2 1962

MONUMENTATION:           Survey Disk                               VM#:     3253
AGENCY:                                                            PID#:  FW0136
SETTING CLASSIFICATION:  Concrete Post


The bench mark is 200 feet west of the centerline of Main Street, 38 feet south
of the north boundary (an east-west fence) of the Coast Guard Station, and at
the base of a flag pole.  The bench mark is set flush in concrete.



                         BENCH MARK STAMPING:  NO 3 1962

MONUMENTATION:           Survey Disk                               VM#:     3254
AGENCY:                                                            PID#:  FW0135
SETTING CLASSIFICATION:  Concrete Porch


The bench mark is set in a concrete porch, located 0.5 mile south of
Chincoteague bridge (Virginia 175), just north of the Coast Guard Station
driveway, 27 feet west of the centerline of Main Street and located on the
southwest corner of the concrete porch of Conant Brothers Hardware Store.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  4

                                                   PUBLICATION DATE:  01/11/1982
Station ID: 8630249                                SUPERCEDED DATE:   04/21/2003
Name:       U.S.C.G STATION, CHINCOTEAGUE ISLAND              
            VIRGINIA
NOAA Chart: 12211                                  Latitude:         37° 55.9' N
USGS Quad:  CHINCOTEAGUE WEST                      Longitude:        75° 23.0' W


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


                         BENCH MARK STAMPING:  TIDAL BM NO 1 1976

MONUMENTATION:           Survey Disk                               VM#:     3255
AGENCY:                                                            PID#:  FW0614
SETTING CLASSIFICATION:  Concrete Retaining Wall


The bench mark is set in the top of a concrete retaining wall at the U.S. Coast
Guard Base, on the north side of a boat ramp, 1.8 feet from the north- west end
of the wall (at the end of a wooden sidewalk), and 0.2 foot above ground.



                         BENCH MARK STAMPING:  TIDAL BM NO 4 1976

MONUMENTATION:           Survey Disk                               VM#:     3256
AGENCY:                                                            PID#:  FW0613
SETTING CLASSIFICATION:  Concrete Post


The bench mark is set in concrete, 37.5 feet northwest of the centerline of Main
Street, 31.5 feet southeast of telephone pole No. NO 1 AH, 10.3 feet southwest
of the centerline of an exit driveway, and 0.2 foot below ground.



                         BENCH MARK STAMPING:  T 421 1963

MONUMENTATION:           Survey Disk                               VM#:     3257
AGENCY:                                                            PID#:  FW0139
SETTING CLASSIFICATION:  Concrete Post


The bench mark is set in a concrete post from the junction of State Highway 175
and Main Street at Chincoteague, 1.0 mile southwest along Main Street, 67.5 feet
west-northwest and across the street from the northwest corner of a pink,
one-story, block house, 26 feet west of the centerline of Main Street, 5.5 feet
north-northeast of power pole No. 34 H-6MX, and 0.2 foot above ground level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  4

                                                   PUBLICATION DATE:  01/11/1982
Station ID: 8630249                                SUPERCEDED DATE:   04/21/2003
Name:       U.S.C.G STATION, CHINCOTEAGUE ISLAND              
            VIRGINIA
NOAA Chart: 12211                                  Latitude:         37° 55.9' N
USGS Quad:  CHINCOTEAGUE WEST                      Longitude:        75° 23.0' W


                            T I D A L   D A T U M S 


Tidal datums at U.S.C.G STATION, CHINCOTEAGUE ISLAND based on:

     LENGTH OF SERIES:      1 YEAR
     TIME PERIOD:           FEB 1977 - JAN 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8638610 Hampton Roads, Virginia


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

     MEAN HIGHER HIGH WATER                     MHHW   =   1.85
     MEAN HIGH WATER                            MHW    =   1.71
     MEAN TIDE LEVEL                            MTL    =   0.90
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   0.64
     MEAN LOW WATER                             MLW    =   0.09
     MEAN LOWER LOW WATER                       MLLW   =   0.00

   *  NGVD reference based on adjustment of 1973 and NOS levels of 1977. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 2 1962                                   4.84      3.13
     NO 3 1962                                   5.42      3.71
     TIDAL BM NO 1 1976                          4.70      2.99
     TIDAL BM NO 4 1976                          4.53      2.82
     T 421 1963                                  4.00      2.29


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

                                                   PUBLICATION DATE:  01/11/1982
Station ID: 8630249                                SUPERCEDED DATE:   04/21/2003
Name:       U.S.C.G STATION, CHINCOTEAGUE ISLAND              
            VIRGINIA
NOAA Chart: 12211                                  Latitude:         37° 55.9' N
USGS Quad:  CHINCOTEAGUE WEST                      Longitude:        75° 23.0' W


                             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 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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