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Bench Mark Sheet for 9462676, Broad Bight 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 9462676                         PUBLICATION DATE:  11/07/2013
Name:       BROAD BIGHT                                       
            AK
NOAA Chart: 16531                           Latitude:   54°  3.9' N (  54.06458)
USGS Quad:  UNIMAK A-6                      Longitude: 165° 56.2' W (-165.93706)


To reach the tidal bench marks from the Unalaska (Dutch Harbor) City Dock by
boat, proceed NNE 14.0 km (7.6 nm) to Priest Rock, then proceed E for 28.2 km
(15.2 nm) crossing Akutan Pass past Cape Morgan to the N, then proceed N 1.2 km
(0.7 nm) into Broad Bight which is the first beach W of Battery Point on the S
end of Akutan Island. The tide gauge is located on the W end of Broad Bight on a
rock outcrop 0.3 km (0.2 nm) S of the stream mouth, and the bench marks are on
the rock outcrop and boulders along the cliff face to the N.


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


                 PRIMARY BENCH MARK STAMPING:  2676 A 2013
                         DESIGNATION:          946 2676 A

MONUMENTATION:           Tidal Station disk                    VM#:        20818
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID#: BBDC14
LATITUDE:   54°  3.9' N (  54.06447)          LONGITUDE: 165° 56.2' W (-165.93717)


The primary bench mark is a disk set in the seaward high point of a bedrock
outcrop below a rock bluff and S of the stream at the W end of Broad Bight,
31.93 m (104.8 ft) S of the high point of the N most extent of this rock ledge,
16.66 m (54.7 ft) SSE of the grass above the sandy hollow below the rock bluff,
and 14.37 m (47.1 ft) SE of the rock bluff nearest the bench mark.

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

                                                                                
Station ID: 9462676                         PUBLICATION DATE:  11/07/2013
Name:       BROAD BIGHT                                       
            AK
NOAA Chart: 16531                           Latitude:   54°  3.9' N (  54.06458)
USGS Quad:  UNIMAK A-6                      Longitude: 165° 56.2' W (-165.93706)


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


                         BENCH MARK STAMPING:  2676 B 2013
                         DESIGNATION:          946 2676 B

MONUMENTATION:           Tidal Station disk                    VM#:        20819
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Boulder                               OPUS PID:        
LATITUDE:   54°  3.9' N (  54.06503)          LONGITUDE: 165° 56.2' W (-165.93725)


The bench mark is a disk set in a boulder 2.00 m (6.5 ft) wide and 0.30 m (1.0
ft) high embedded in black sand inside of a small lagoon S of the mouth of a
stream and at the base of a 30 m (100 ft) high rock bluff at the W end of Broad
Bight, 31.49 m (130.3 ft) NW of the S edge of the shallow rock lagoon along the
rock outcrop, 22.50 m (73.8 ft) SSE of the N end of the rock bluff, 18.20 m
(59.7 ft) W of the highest rock outcrop along the edge of the stream at low
tide, 1.96 m (6.4  ft) ENE of the rock bluff, and 0.39 m (1.3 ft) above the
beach.



                         BENCH MARK STAMPING:  2676 C 2013
                         DESIGNATION:          946 2676 C

MONUMENTATION:           Tidal Station disk                    VM#:        20820
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Boulder                               OPUS PID:        
LATITUDE:   54°  3.9' N (  54.06539)          LONGITUDE: 165° 56.3' W (-165.93811)


The bench mark is a disk set in a 2.00 m (6.5 ft) wide conglomerate boulder W of
the stream at the W end of Broad Bight, 83.40 m (273.6 ft) SW of the W bank of
the stream near the mouth, 36.60 m (120.1 ft) N of the N end of the rock bluff ,
2.85 m (9.35 ft) E of vegetation, and 1.40 m (4.3 ft) above rocky ground covered
in kelp.

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

                                                                                
Station ID: 9462676                         PUBLICATION DATE:  11/07/2013
Name:       BROAD BIGHT                                       
            AK
NOAA Chart: 16531                           Latitude:   54°  3.9' N (  54.06458)
USGS Quad:  UNIMAK A-6                      Longitude: 165° 56.2' W (-165.93706)


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


                         BENCH MARK STAMPING:  2676 D 2013
                         DESIGNATION:          946 2676 D

MONUMENTATION:           Tidal Station disk                    VM#:        20821
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Boulder                               OPUS PID:        
LATITUDE:   54°  4.0' N (  54.06592)          LONGITUDE: 165° 56.3' W (-165.93836)


The bench mark is a disk set in a rock at the base of a cliff on black sand amid
grass W of the stream at the W end of Broad Bight, 91.10 m (298.9 ft) W of W
stream bank, and 7.20 m (23.6 ft) ESE of cliff.



                         BENCH MARK STAMPING:  2676 E 2013
                         DESIGNATION:          946 2676 E

MONUMENTATION:           Tidal Station disk                    VM#:        20822
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Boulder                               OPUS PID:        
LATITUDE:   54°  4.0' N (  54.06647)          LONGITUDE: 165° 56.3' W (-165.93806)


The bench mark is a disk set in a 4.00 m (13.1 ft) square rock boulder at base
of cliff in grass W of the stream at the W end of Broad Bight, 77.0 m (252.6 ft)
WNW of W stream bank, 5.30 m (17.4 ft) SE of cliff, and 2.10 m (6.9 ft) above
ground.

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

                                                                                
Station ID: 9462676                         PUBLICATION DATE:  11/07/2013
Name:       BROAD BIGHT                                       
            AK
NOAA Chart: 16531                           Latitude:   54°  3.9' N (  54.06458)
USGS Quad:  UNIMAK A-6                      Longitude: 165° 56.2' W (-165.93706)


                            T I D A L   D A T U M S 


Tidal datums at BROAD BIGHT based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           June 2013 - July 2013
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9459881 KING COVE, DEER PASSAGE, PACIFIC OCEAN


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

     MEAN HIGHER HIGH WATER                     MHHW   =  1.694
     MEAN HIGH WATER                            MHW    =  1.534
     MEAN TIDE LEVEL                            MTL    =  0.987
     MEAN SEA LEVEL                             MSL    =  0.970
     MEAN LOW WATER                             MLW    =  0.439
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     2676 A 2013                                 6.824    5.290
     2676 B 2013                                 2.524    0.990
     2676 C 2013                                 3.607    2.073
     2676 D 2013                                 4.102    2.568
     2676 E 2013                                 8.976    7.442


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

                                                                                
Station ID: 9462676                         PUBLICATION DATE:  11/07/2013
Name:       BROAD BIGHT                                       
            AK
NOAA Chart: 16531                           Latitude:   54°  3.9' N (  54.06458)
USGS Quad:  UNIMAK A-6                      Longitude: 165° 56.2' W (-165.93706)


                             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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Revised: 08/08/2018
NOAA / National Ocean Service
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