Superseded Bench Mark Sheet for 9452346, Cove Point

Present Epoch

Printable version

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

                                                   PUBLICATION DATE:  11/27/2000
Station ID: 9452346                                SUPERCEDED DATE:   04/21/2003
Name:       COVE POINT, BERNER'S BAY                          
            ALASKA
NOAA Chart: 17316                                  Latitude:         58° 45.1' N
USGS Quad:  JUNEAU (D-4)                           Longitude:       135°  1.2' W


To reach the tidal bench marks, proceed to the southern edge of Cove Point in
Berner's Bay, AK. The bench marks are located along the beach in the vicinity,
and the tide gauge was located on a high rock ledge jutting out from the tree
line, and set approximately 15 m above the apparent high water line.


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


                 PRIMARY BENCH MARK STAMPING:  2346 C 1998
                         DESIGNATION:          945 2346 C

MONUMENTATION:           Tidal Station disk                        VM#:    14036
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Bedrock


The primary bench mark is a disk set on top of a 0.46 m x 0.46 m (1.5 ft x 1.5
ft) flat black bedrock shelf-like feature, just at the base of the cliff before
it begins a gradual rise, on the southern edge of Cove Point, at the tip of a
prominent, wedge-shaped, 5 to 9 m (15 to 30 ft) high rock cliff that juts out
from below the treeline, 30 m (98 ft) SE (160 degrees magnetic) from bench mark
2346 D 1998, and approximately at or slightly below the apparent highwater line.



                         BENCH MARK STAMPING:  2346 A 1998
                         DESIGNATION:          945 2346 A

MONUMENTATION:           Tidal Station disk                        VM#:    14034
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Boulder


The bench mark is a disk set on top of a boulder at the base of a rock cliff on
the southern edge of Cove Point, 65 m (213 ft) NE (135 degrees magnetic) from
bench mark 2346 B 1998, and approximately 1 m (3 ft) above the apparent high
water line.

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

                                                   PUBLICATION DATE:  11/27/2000
Station ID: 9452346                                SUPERCEDED DATE:   04/21/2003
Name:       COVE POINT, BERNER'S BAY                          
            ALASKA
NOAA Chart: 17316                                  Latitude:         58° 45.1' N
USGS Quad:  JUNEAU (D-4)                           Longitude:       135°  1.2' W


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


                         BENCH MARK STAMPING:  2346 B 1998
                         DESIGNATION:          945 2346 B

MONUMENTATION:           Tidal Station disk                        VM#:    14035
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set on top of a 0.3 m (1 ft) wide rock shelf feature at
the base of a rock cliff, at knee level, on the southern edge of Cove Point, 42
m (138 ft) NE (078 degrees magnetic) from bench mark 2346 C 1998, and
approximately 1 m (3 ft) above the apparent high water line.



                         BENCH MARK STAMPING:  2346 D 1998
                         DESIGNATION:          945 2346 D

MONUMENTATION:           Tidal Station disk                        VM#:    14037
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Boulder


The bench mark is a disk set on top of a 1 m x 1 m (3 ft x 3 ft) flat section of
a boulder cluster among the cluster of angular dark-colored boulders located 30
m (98 ft) due west of the tip of the prominent wedge-shaped rock cliff on the
southern edge of Cove Point, 27 m (89 ft) NE (065 degrees magnetic) from bench
mark 2346 E 1998, and approximately at or slightly above the apparent high water
line.

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

                                                   PUBLICATION DATE:  11/27/2000
Station ID: 9452346                                SUPERCEDED DATE:   04/21/2003
Name:       COVE POINT, BERNER'S BAY                          
            ALASKA
NOAA Chart: 17316                                  Latitude:         58° 45.1' N
USGS Quad:  JUNEAU (D-4)                           Longitude:       135°  1.2' W


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


                         BENCH MARK STAMPING:  2346 E 1998
                         DESIGNATION:          945 2346 E

MONUMENTATION:           Tidal Station disk                        VM#:    14038
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set on top of a gray rock outcrop that is partially
obscured by grass and weeds, 1 to 2 m (3 to 6 ft) into the tree line, at a small
rocky beach area, on the southern edge of Cove Point, 27 m (89 ft) SW (245
degrees magnetic) from bench mark 2346 D 1998, and approximately 2 m (6 ft)
above the apparent high water line.

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

                                                   PUBLICATION DATE:  11/27/2000
Station ID: 9452346                                SUPERCEDED DATE:   04/21/2003
Name:       COVE POINT, BERNER'S BAY                          
            ALASKA
NOAA Chart: 17316                                  Latitude:         58° 45.1' N
USGS Quad:  JUNEAU (D-4)                           Longitude:       135°  1.2' W


                            T I D A L   D A T U M S 


Tidal datums at COVE POINT, BERNER'S BAY based on:

     LENGTH OF SERIES:      113 hws and 114 lws
     TIME PERIOD:           April 5, 1999 - June 2, 1999
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9452400 SKAGWAY, TAIYA INLET


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

     MEAN HIGHER HIGH WATER                     MHHW   =  4.940
     MEAN HIGH WATER                            MHW    =  4.651
     MEAN SEA LEVEL                             MSL    =  2.612
     MEAN TIDE LEVEL                            MTL    =  2.570
     MEAN LOW WATER                             MLW    =  0.489
     MEAN LOWER LOW WATER                       MLLW   =  0.000



Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     2346 C 1998                                 5.096    0.445
     2346 A 1998                                 7.143    2.492
     2346 B 1998                                 5.283    0.632
     2346 D 1998                                 5.679    1.028
     2346 E 1998                                 7.678    3.027


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

                                                   PUBLICATION DATE:  11/27/2000
Station ID: 9452346                                SUPERCEDED DATE:   04/21/2003
Name:       COVE POINT, BERNER'S BAY                          
            ALASKA
NOAA Chart: 17316                                  Latitude:         58° 45.1' N
USGS Quad:  JUNEAU (D-4)                           Longitude:       135°  1.2' W


Foot Notes:

Portions of SE Alaska in the  area of  Lynn Canal and Stephens Passage have
anomalous relative sea level trends compared to most other geographic regions in
the United States. This is due to a general uplift of the land in this area,
which has been occurring at a rapid rate.  Because of the magnitude of the sea
level trends in these areas, NOAA has adopted a procedure for computing accepted
tidal datums for the National Water Level Observation Network (NWLON) using the
last several years of sea level data rather than the 19 - year tidal epoch. The
tide ranges are still based on the 1960 - 1978 National Tidal Datum Epoch (NTDE)
and are applied to the five year (1994 - 1998) Mean Tide Level (MTL) to compute
other tidal datums. The adoption of this procedure was necessary to ensure that
these tidal datums accurately represent the existing stand of sea level.

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

                                                   PUBLICATION DATE:  11/27/2000
Station ID: 9452346                                SUPERCEDED DATE:   04/21/2003
Name:       COVE POINT, BERNER'S BAY                          
            ALASKA
NOAA Chart: 17316                                  Latitude:         58° 45.1' N
USGS Quad:  JUNEAU (D-4)                           Longitude:       135°  1.2' 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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