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Bench Mark Sheet for 9458762, UNAVIKSHAK ISLAND AK

Superseded Epoch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Small blue map location marker Unpublished bench mark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  5

                                                                                
Station ID: 9458762                         PUBLICATION DATE:  04/29/2004
Name:       UNAVIKSHAK ISLAND                                 
            AK
NOAA Chart: 16566                           Latitude:   56° 29.5' N (  56.49170)
USGS Quad:  SUTWIK ISLAND (B-6)             Longitude: 157° 44.4' W (-157.74000)


To reach the tidal bench marks from Cape Kumliun on the Alaska Peninsula, go 5.6
km (3.5 mi)  east to Unavikshak Island which is located 4.6 km (2.9 mi) NE of a
small charted island.  The tide gage and staff were located on the SW side of
the Unavikshak island, below the southern-most of three hills.  The bench marks
were evenly spaced between two ledges pointing toward Cape Kumliun.


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


                 PRIMARY BENCH MARK STAMPING:  8762 A 1997
                         DESIGNATION:          945 8762 A

MONUMENTATION:           Tidal Station disk                    VM#:        13711
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   56° 29.5' N (  56.49170)          LONGITUDE: 157° 44.4' W (-157.74000)


The primary bench mark is a disk set flush in bedrock on the southern side of a
prominent rock outcrop, 90 m (295 ft) NE of bench mark 8762 B 1997, 3 m (10 ft)
from the cliff face, and 3 m (10 ft) above the high water line.



                         BENCH MARK STAMPING:  8762 B 1997
                         DESIGNATION:          945 8762 B

MONUMENTATION:           Tidal Station disk                    VM#:        13712
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   56° 29.5' N (  56.49170)          LONGITUDE: 157° 44.4' W (-157.74000)


The bench mark is a disk set flush in bedrock on a ledge, 90 m (295 ft) NE of
bench mark 8762 C 1997, 5 m (16 ft) from the cliff face, and 2 m (7 ft) above
the high water line.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 9458762                         PUBLICATION DATE:  04/29/2004
Name:       UNAVIKSHAK ISLAND                                 
            AK
NOAA Chart: 16566                           Latitude:   56° 29.5' N (  56.49170)
USGS Quad:  SUTWIK ISLAND (B-6)             Longitude: 157° 44.4' W (-157.74000)


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


                         BENCH MARK STAMPING:  8762 C 1997
                         DESIGNATION:          945 8762 C

MONUMENTATION:           Tidal Station disk                    VM#:        13713
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56° 29.5' N (  56.49170)          LONGITUDE: 157° 44.4' W (-157.74000)


The bench mark is a disk set flush in the NE corner of a rock outcrop, 70 m (230
ft) NE of bench mark 8762 D 1997, 2 m (5 ft) from the cliff face, and 1 m (3 ft)
above the high water line.



                         BENCH MARK STAMPING:  8762 D 1997
                         DESIGNATION:          945 8762 D

MONUMENTATION:           Tidal Station disk                    VM#:        13714
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock cliff ledge                      OPUS PID:        
LATITUDE:   56° 29.5' N (  56.49170)          LONGITUDE: 157° 44.4' W (-157.74000)


The bench mark is a disk set flush in the base of a sloped cliff ledge, 100 m
(328 ft) NE of bench mark 8762 E 1997, 2 m (7 ft) from the cliff face, and 0.50
m (1.6 ft) above the high water line.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 9458762                         PUBLICATION DATE:  04/29/2004
Name:       UNAVIKSHAK ISLAND                                 
            AK
NOAA Chart: 16566                           Latitude:   56° 29.5' N (  56.49170)
USGS Quad:  SUTWIK ISLAND (B-6)             Longitude: 157° 44.4' W (-157.74000)


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


                         BENCH MARK STAMPING:  8762 E 1997
                         DESIGNATION:          945 8762 E

MONUMENTATION:           Tidal Station disk                    VM#:        13715
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56° 29.5' N (  56.49170)          LONGITUDE: 157° 44.4' W (-157.74000)


The bench mark is a disk set flush in the northern-most outcrop of a cluster of
prominent rock outcrops, 100 m (328 ft) SE of bench mark 8762 D 1997, 25 m (82
ft) from the cliff face, and 1 m (3 ft) below the high water line.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 9458762                         PUBLICATION DATE:  04/29/2004
Name:       UNAVIKSHAK ISLAND                                 
            AK
NOAA Chart: 16566                           Latitude:   56° 29.5' N (  56.49170)
USGS Quad:  SUTWIK ISLAND (B-6)             Longitude: 157° 44.4' W (-157.74000)


                            T I D A L   D A T U M S 


Tidal datums at UNAVIKSHAK ISLAND based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           July 1997 - August 1997
     TIDAL EPOCH:           1983-2001
     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   =  2.767
     MEAN HIGH WATER                            MHW    =  2.510
     MEAN TIDE LEVEL                            MTL    =  1.464
     MEAN SEA LEVEL                             MSL    =  1.435
     MEAN LOW WATER                             MLW    =  0.419
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     8762 A 1997                                 3.404    0.894
     8762 B 1997                                 3.683    1.173
     8762 C 1997                                 3.401    0.891
     8762 D 1997                                 2.814    0.304
     8762 E 1997                                 2.377   -0.133


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

                                                                                
Station ID: 9458762                         PUBLICATION DATE:  04/29/2004
Name:       UNAVIKSHAK ISLAND                                 
            AK
NOAA Chart: 16566                           Latitude:   56° 29.5' N (  56.49170)
USGS Quad:  SUTWIK ISLAND (B-6)             Longitude: 157° 44.4' W (-157.74000)


                             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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Products available at 9458762 UNAVIKSHAK ISLAND, AK

Revised: 10/15/2013
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services