Superseded Bench Mark Sheet for 8638888, VA. PILOTS DOCK, LYNNHAVEN INLET 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:  08/18/1988
Station ID: 8638888                                SUPERCEDED DATE:   04/21/2003
Name:       LYNNHAVEN PILOTS DOCK, LYNNHAVEN INLET            
            VIRGINIA
NOAA Chart: 12254                                  Latitude:         36° 54.4' N
USGS Quad:  CAPE HENRY                             Longitude:        76°  5.4' W


To reach the tidal bench marks from the intersection of U.S. Highways 13 and 60
near the southern end of the Chesapeake Bay Bridge Tunnel, proceed east on U.S.
Highway 60 to the bridge over Lynnhaven Inlet.  The bench marks are in the
vicinity of The Virginia Pilots Association dock and Bubbas Marina.  The tide
gage and staff were on the Pilots Association dock.


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


                 PRIMARY BENCH MARK STAMPING:  NO 3 1963

MONUMENTATION:           Survey Disk                               VM#:     3473
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Block


The bench mark is set in a 4 x 12-foot (1x4 m) concrete block which is 18 feet
(5 m) deep, 57 feet (17 m) NW of Bench Mark NO 2 1963, 2 feet (1 m) NW of the SW
corner of a house, and at ground level.



                         BENCH MARK STAMPING:  NO 2 1963

MONUMENTATION:           Survey Disk                               VM#:     3472
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Bulkhead


The bench mark is set in the concrete bulkhead on the west side of the boat ramp
at the Pilots Association dock, and 3 feet (1 m) south of the north end of the
bulkhead.

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

                                                   PUBLICATION DATE:  08/18/1988
Station ID: 8638888                                SUPERCEDED DATE:   04/21/2003
Name:       LYNNHAVEN PILOTS DOCK, LYNNHAVEN INLET            
            VIRGINIA
NOAA Chart: 12254                                  Latitude:         36° 54.4' N
USGS Quad:  CAPE HENRY                             Longitude:        76°  5.4' W


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


                         BENCH MARK STAMPING:  NO 4 1970

MONUMENTATION:           Survey Disk                               VM#:    12420
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Concrete Slab


The bench mark is set in a 4 x 5-foot (1x2 m) concrete slab at the bottom of the
steps to Bubbas Marina, east of the Pilots Association dock on the south side of
Highway 60.

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

                                                   PUBLICATION DATE:  08/18/1988
Station ID: 8638888                                SUPERCEDED DATE:   04/21/2003
Name:       LYNNHAVEN PILOTS DOCK, LYNNHAVEN INLET            
            VIRGINIA
NOAA Chart: 12254                                  Latitude:         36° 54.4' N
USGS Quad:  CAPE HENRY                             Longitude:        76°  5.4' W


                            T I D A L   D A T U M S 


Tidal datums at LYNNHAVEN PILOTS DOCK, LYNNHAVEN INLET based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           DECEMBER 1977
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8638610 HAMPTON ROADS


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

     HIGHEST OBSERVED WATER LEVEL (12/19/1977)         =   4.88
     MEAN HIGHER HIGH WATER                     MHHW   =   2.64
     MEAN HIGH WATER                            MHW    =   2.35
     MEAN TIDE LEVEL                            MTL    =   1.24
     MEAN LOW WATER                             MLW    =   0.13
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (01/11/1978)         =  -1.78



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 3 1963                                   8.23      5.88
     NO 2 1963                                   7.23      4.88
     NO 4 1970                                  12.52     10.17


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

                                                   PUBLICATION DATE:  08/18/1988
Station ID: 8638888                                SUPERCEDED DATE:   04/21/2003
Name:       LYNNHAVEN PILOTS DOCK, LYNNHAVEN INLET            
            VIRGINIA
NOAA Chart: 12254                                  Latitude:         36° 54.4' N
USGS Quad:  CAPE HENRY                             Longitude:        76°  5.4' 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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