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Bench Mark Sheet for 9462786, SE Tigalda Island, Pacific Ocean 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 9462786                         PUBLICATION DATE:  11/07/2013
Name:       SE TIGALDA ISLAND, PACIFIC OCEAN                  
            AK
NOAA Chart: 16531                           Latitude:   54°  6.1' N (  54.10181)
USGS Quad:  Unimak A-3                      Longitude: 164° 56.5' W (-164.94158)


To reach the tidal bench marks from the Unalaska (Dutch Harbor) City Dock,
proceed NNE 14.0 km (7.6 nm) to Priest Rock, then proceed east for 33.6 km (18.1
nm) crossing Akutan Pass to Battery Point on the southern point of Akutan
Island, then proceed 22.2 km (12.0 nm) ESE to the south side of Rootok Island,
continue east 39.8 km (21.5 nm) along the south side of Avatanak Island and
Tigalda Island until the southern shore of Tigalda Island turns NE, then proceed
NE 3.7 km (2.0 nm) to a small unnamed bay. The bench marks are on the north side
of the bay continuing west to the head of the bay and a natural rock arch. The
tide gauge orifices are located on a bedrock outcrop just east of the natural
rock arch and the tide gauges are located on the grassy top of the rock arch.


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


                 PRIMARY BENCH MARK STAMPING:  2786 C 2013
                         DESIGNATION:          946 2786 C

MONUMENTATION:           Tidal Station disk                    VM#:        20829
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   54°  6.1' N (  54.10236)          LONGITUDE: 164° 56.5' W (-164.94097)


The primary bench mark is a disk set in bedrock below a 10m high rock bluff and
above a cobble beach, 52.00 m (170.6 ft) west of a water fall, 6.63 m (21.8 ft)
WNW of the east end of a 11.5 m (38 ft) long bedrock outcrop 3m high and
oriented east to west, 5.80 m NE of the west end of the same rock outcrop, and
4.85 m (15.9 ft) south of the rock bluff.

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

                                                                                
Station ID: 9462786                         PUBLICATION DATE:  11/07/2013
Name:       SE TIGALDA ISLAND, PACIFIC OCEAN                  
            AK
NOAA Chart: 16531                           Latitude:   54°  6.1' N (  54.10181)
USGS Quad:  Unimak A-3                      Longitude: 164° 56.5' W (-164.94158)


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


                         BENCH MARK STAMPING:  2786 B 2013
                         DESIGNATION:          946 2786 B

MONUMENTATION:           Tidal Station disk                    VM#:        20828
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   54°  6.1' N (  54.10231)          LONGITUDE: 164° 56.4' W (-164.94008)


The bench mark is a disk set in bedrock on the north side of the small unnamed
bay, 8.0 m (26.2 ft) SE of a 5 m (16 ft) high waterfall, 7.92 m (26.0 ft) NNE of
the seaward most high point of the same rock outcrop, 5.15 m (16.9 ft) SSW of
the rock bluff and 3.75 m (12.3 ft) ESE of the west edge of the rock outcrop
along the east side of the stream. 



                         BENCH MARK STAMPING:  2786 A 2013
                         DESIGNATION:          946 2786 A

MONUMENTATION:           Tidal Station disk                    VM#:        20830
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID#: BBDC13
LATITUDE:   54°  6.1' N (  54.10190)          LONGITUDE: 164° 56.4' W (-164.93937)


The bench mark is a disk set in bedrock on the north side of a small unnamed bay
on the east side of Tigalda Island, 22.84 m (74.9 ft) WNW of the west end of the
bedrock outcrop at approximately the same elevation, 12.13 m (40.0 ft) SSW of
the vegetation line, 11.05 m (36.2 ft) NNE of the top of the black bedrock
outcrop with yellow-green lichen, and 1.33 m (4.4 ft) ESE of the west end of the
rock point in which the disk is set.

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

                                                                                
Station ID: 9462786                         PUBLICATION DATE:  11/07/2013
Name:       SE TIGALDA ISLAND, PACIFIC OCEAN                  
            AK
NOAA Chart: 16531                           Latitude:   54°  6.1' N (  54.10181)
USGS Quad:  Unimak A-3                      Longitude: 164° 56.5' W (-164.94158)


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


                         BENCH MARK STAMPING:  2786 D 2013
                         DESIGNATION:          946 2786 D

MONUMENTATION:           Tidal Station disk                    VM#:        20831
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   54°  6.1' N (  54.10203)          LONGITUDE: 164° 56.5' W (-164.94178)


The bench mark is a disk set in a 2 m (6 ft) long by 2 m (6 ft) wide boulder on
a cobble beach at the head of the small unnamed bay, 23.30 m (76.4 ft) north of
the center of the natural rock arch at the head of the bay, 17.93 m (58.8 ft)
SSW of a rock point that extends seaward from the rock cliff above the cobble
beach, 16.33 m (53.6 ft) ESE of the vegetation line, and 1.15 m (3.8 ft) above
the cobble beach.



                         BENCH MARK STAMPING:  2786 E 2013
                         DESIGNATION:          946 2786 E

MONUMENTATION:           Tidal Station disk                    VM#:        20832
AGENCY:                  National Ocean Service                IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   54°  6.1' N (  54.10142)          LONGITUDE: 164° 56.5' W (-164.94194)


The bench mark is a disk set in a rock outcrop surrounded by water at high tide,
26.10 m (85.6 ft) SSW of the natural rock arch at the head of the bay, 25.30 m
(83.0 ft) SE of the rock point at the base of the grass and rock bluff above the
cobble beach, 4.64 m (15.2 ft) WNW of the seaward extent of the rock outcrop,
and 2.20 m (7.2 ft) east of the high point of the rock outcrop.

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

                                                                                
Station ID: 9462786                         PUBLICATION DATE:  11/07/2013
Name:       SE TIGALDA ISLAND, PACIFIC OCEAN                  
            AK
NOAA Chart: 16531                           Latitude:   54°  6.1' N (  54.10181)
USGS Quad:  Unimak A-3                      Longitude: 164° 56.5' W (-164.94158)


                            T I D A L   D A T U M S 


Tidal datums at SE TIGALDA ISLAND, PACIFIC OCEAN 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   =  1.614
     MEAN HIGH WATER                            MHW    =  1.434
     MEAN TIDE LEVEL                            MTL    =  0.919
     MEAN SEA LEVEL                             MSL    =  0.901
     MEAN LOW WATER                             MLW    =  0.403
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     2786 C 2013                                 3.440    2.006
     2786 B 2013                                 2.642    1.208
     2786 A 2013                                 4.372    2.938
     2786 D 2013                                 3.157    1.723
     2786 E 2013                                 2.389    0.955


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

                                                                                
Station ID: 9462786                         PUBLICATION DATE:  11/07/2013
Name:       SE TIGALDA ISLAND, PACIFIC OCEAN                  
            AK
NOAA Chart: 16531                           Latitude:   54°  6.1' N (  54.10181)
USGS Quad:  Unimak A-3                      Longitude: 164° 56.5' W (-164.94158)


                             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 9462786 SE Tigalda Island, Pacific Ocean, AK

Revised: 08/08/2018
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services