Superseded Bench Mark Sheet for 9456992, TAKLI ISLAND, SHELIKOF STRAIT AK

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:  09/27/2001
Station ID: 9456992                                SUPERCEDED DATE:   04/21/2003
Name:       TAKLI ISLAND                                      
            ALASKA
NOAA Chart: 16576                                  Latitude:         58°  3.8' N
USGS Quad:  Mount Katmai (A-2)                     Longitude:       154° 28.6' W


To reach the tidal bench marks proceed by boat to Takli Island, which is located
at the entrance to Amalik Bay in Shelikof Straits.  The bench marks are located
at the north end of a prominent peninsula on the NE end of the Island.  The tide
gage was mounted on the rock cliff with the orifice and tubing extending 15.24 m
(50.0 ft) offshore.  


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


                 PRIMARY BENCH MARK STAMPING:  TIDAL 1
                         DESIGNATION:          945 6992 TIDAL 1

MONUMENTATION:           Tidal Station disk                        VM#:     9642
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Rock outcrop


The primary bench mark is a disk set flush in a rounded 3 m (10 ft) diameter
rock on the north end of a prominent peninsula on the NE end of the island, 21 m
(70 ft) NW of a rock cliff, NE (44 degrees per magnetic compass) of the eastern
cliff of a prominent wedge shaped island, and is submerged at high water.



                         BENCH MARK STAMPING:  TIDAL 2
                         DESIGNATION:          945 6992 TIDAL 2

MONUMENTATION:           Tidal Station disk                        VM#:     9643
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set flush in a rounded 2 m (6 ft) diameter rock on the
north end of a promonent peninsula on the NE end of the island, 30 m (97 ft) SSE
(152 degrees per magnetic compass) of bench mark Tidal 1, 5 m (15 ft) from the
base of a rock cliff, and is submerged at high water.

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

                                                   PUBLICATION DATE:  09/27/2001
Station ID: 9456992                                SUPERCEDED DATE:   04/21/2003
Name:       TAKLI ISLAND                                      
            ALASKA
NOAA Chart: 16576                                  Latitude:         58°  3.8' N
USGS Quad:  Mount Katmai (A-2)                     Longitude:       154° 28.6' W


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


                         BENCH MARK STAMPING:  TIDAL 3
                         DESIGNATION:          945 6992 TIDAL 3

MONUMENTATION:           Tidal Station disk                        VM#:     9644
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set flush in a rounded 2 m (8 ft) diameter rock on the
north end of a prominent peninsula on the NE end of the island, 25 m (83 ft) SSE
(160 degrees per magnetic compass) of bench mark Tidal 2, 6 m (20 ft) west of
the base of a rock cliff, and is submerged at high water.



                         BENCH MARK STAMPING:  TIDAL 4
                         DESIGNATION:          945 6992 TIDAL 4

MONUMENTATION:           Tidal Station disk                        VM#:     9645
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set flush in a 2 m (6 ft) diameter diamond shaped rock
on the north end of a prominent peninsula on the NE end of the island, 54 m (176
ft) SE (140 degrees per magnetic compass) of bench mark Tidal 3, 8 m (25 ft)
west of the base of a rock cliff, and is submerged at high water.



                         BENCH MARK STAMPING:  TIDAL 5
                         DESIGNATION:          945 6992 TIDAL 5

MONUMENTATION:           Tidal Station disk                        VM#:     9646
AGENCY:                  National Ocean Survey (NOS)               PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set flush in a 1 m (2 ft) square flat topped rock on
the north end of a prominent peninsula on the NE end of the island, 34 m (110
ft) SE (130 degrees per magnetic compass) from bench mark Tidal 4, and is at the
base of a rock cliff.

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

                                                   PUBLICATION DATE:  09/27/2001
Station ID: 9456992                                SUPERCEDED DATE:   04/21/2003
Name:       TAKLI ISLAND                                      
            ALASKA
NOAA Chart: 16576                                  Latitude:         58°  3.8' N
USGS Quad:  Mount Katmai (A-2)                     Longitude:       154° 28.6' W


                            T I D A L   D A T U M S 


Tidal datums at TAKLI ISLAND based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           June 1980 - August 1980
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9459450 SAND POINT, POPOF ISLAND


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

     MEAN HIGHER HIGH WATER                     MHHW   =  4.133
     MEAN HIGH WATER                            MHW    =  3.852
     MEAN TIDE LEVEL                            MTL    =  2.181
     MEAN LOW WATER                             MLW    =  0.510
     MEAN LOWER LOW WATER                       MLLW   =  0.000



Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     TIDAL 1                                     2.616   -1.236
     TIDAL 2                                     3.357   -0.495
     TIDAL 3                                     2.592   -1.260
     TIDAL 4                                     2.545   -1.307
     TIDAL 5                                     4.505    0.653


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

                                                   PUBLICATION DATE:  09/27/2001
Station ID: 9456992                                SUPERCEDED DATE:   04/21/2003
Name:       TAKLI ISLAND                                      
            ALASKA
NOAA Chart: 16576                                  Latitude:         58°  3.8' N
USGS Quad:  Mount Katmai (A-2)                     Longitude:       154° 28.6' 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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