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Bench Mark Sheet for 9454381, BLIGH ISLAND, T-16 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Superseded Epoch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Small blue map location marker Unpublished bench mark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  6

                                                                                
Station ID: 9454381                         PUBLICATION DATE:  07/12/2004
Name:       BLIGH ISLAND, T-16                                
            AK
NOAA Chart: 16708                           Latitude:   60° 48.4' N (  60.80670)
USGS Quad:  CORDOVA D-8                     Longitude: 146° 47.9' W (-146.79800)


To reach the tidal bench marks from the Port Valdez ferry terminal, proceed by
boat WSW along Port Valdez for approximately 17.2 km (9.3 nm) to Valdez Narrows,
then SW along Valdez Arm for approximately 35.6 km (19.2 nm) to the first turn
in the southbound Prince William Sound traffic lane, then ESE for approximately
14.3 km (7.7 nm) to the SW corner of Bligh Island.  The tidal bench marks are in
the cliffs along the small bay formed by a rocky point projecting out from the
SW corner of the island.  The tide gage was on a small wood platform secured to
the rock.  The tide staff was bolted to the rock face.


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


                 PRIMARY BENCH MARK STAMPING:  TIDAL BM 4381-A
                         DESIGNATION:          945 4381 A TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         9505
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   60° 48.4' N (  60.80670)          LONGITUDE: 146° 47.9' W (-146.79800)


The primary bench mark is a disk set flush in the bedrock approximately halfway
out on the rocky point that projects about 76 m (250 ft) from the island, and 18
m (60 ft) NW of bench mark NOS TIDAL BM 4381-B.

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

                                                                                
Station ID: 9454381                         PUBLICATION DATE:  07/12/2004
Name:       BLIGH ISLAND, T-16                                
            AK
NOAA Chart: 16708                           Latitude:   60° 48.4' N (  60.80670)
USGS Quad:  CORDOVA D-8                     Longitude: 146° 47.9' W (-146.79800)


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


                         BENCH MARK STAMPING:  OUT 1901 NO 1 1972
                         DESIGNATION:          OUT RM 1

MONUMENTATION:           Reference Mark disk                   VM#:         9502
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AE7155
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   60° 48.4' N (  60.80670)          LONGITUDE: 146° 47.9' W (-146.79800)


The bench mark is a disk set on the rocky point that projects approximately 76 m
(250 ft) from the island, and is 5.55 m (18.2 ft) NE of bench mark OUT 1901 (NO
STAMPING 1).

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

                                                                                
Station ID: 9454381                         PUBLICATION DATE:  07/12/2004
Name:       BLIGH ISLAND, T-16                                
            AK
NOAA Chart: 16708                           Latitude:   60° 48.4' N (  60.80670)
USGS Quad:  CORDOVA D-8                     Longitude: 146° 47.9' W (-146.79800)


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


                         BENCH MARK STAMPING:  OUT 1901 NO 2 1972
                         DESIGNATION:          OUT RM 2

MONUMENTATION:           Reference Mark disk                   VM#:         9503
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AE7154
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   60° 48.4' N (  60.80670)          LONGITUDE: 146° 47.9' W (-146.79800)


The bench mark is a disk set on the rocky point that projects approximately 76 m
(250 ft) from the island, and is 9.27 m (30.4 ft) west of bench mark OUT 1901
(NO STAMPING 1).



                         BENCH MARK STAMPING:  NOS TIDAL BM 4381-B
                         DESIGNATION:          945 4381 B TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:         9506
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   60° 48.4' N (  60.80670)          LONGITUDE: 146° 47.9' W (-146.79800)


The bench mark is a disk set flush in the bedrock approximately halfway out on
the rocky point that projects about 76 m (250 ft) from the island, 30 m (100 ft)
NE of bench mark OUT 1901 (NO STAMPING 1).

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

                                                                                
Station ID: 9454381                         PUBLICATION DATE:  07/12/2004
Name:       BLIGH ISLAND, T-16                                
            AK
NOAA Chart: 16708                           Latitude:   60° 48.4' N (  60.80670)
USGS Quad:  CORDOVA D-8                     Longitude: 146° 47.9' W (-146.79800)


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


                         BENCH MARK STAMPING:   
                         DESIGNATION:          OUT 1901
                         ALIAS:                NO STAMPING 1

MONUMENTATION:           Bolt                                  VM#:         9507
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AE6485
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   60° 48.4' N (  60.80670)          LONGITUDE: 146° 47.9' W (-146.79800)


The bench mark is a 3 x 5/8-inch copper bolt set in the only flat portion on the
rocky point which projects approximately 76 m (250 ft) from the island, 27 m (89
ft) east of the west tip of the point, 4.79 m (15.7 ft) south of the vegetation
line, and 6 m (20 ft) above the approximate high water line.

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

                                                                                
Station ID: 9454381                         PUBLICATION DATE:  07/12/2004
Name:       BLIGH ISLAND, T-16                                
            AK
NOAA Chart: 16708                           Latitude:   60° 48.4' N (  60.80670)
USGS Quad:  CORDOVA D-8                     Longitude: 146° 47.9' W (-146.79800)


                            T I D A L   D A T U M S 


Tidal datums at BLIGH ISLAND, T-16 based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           July 1977 - July 1977
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9454240 VALDEZ, PRINCE WILLIAM SOUND


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

     MEAN HIGHER HIGH WATER                     MHHW   =  3.688
     MEAN HIGH WATER                            MHW    =  3.410
     MEAN SEA LEVEL                             MSL    =  1.958
     MEAN TIDE LEVEL                            MTL    =  1.933
     MEAN LOW WATER                             MLW    =  0.457
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     TIDAL BM 4381-A                             7.031    3.621
     OUT 1901 NO 1 1972                         12.714    9.304
     OUT 1901 NO 2 1972                         11.892    8.482
     NOS TIDAL BM 4381-B                         7.386    3.976
     OUT 1901                                   10.806    7.396


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

                                                                                
Station ID: 9454381                         PUBLICATION DATE:  07/12/2004
Name:       BLIGH ISLAND, T-16                                
            AK
NOAA Chart: 16708                           Latitude:   60° 48.4' N (  60.80670)
USGS Quad:  CORDOVA D-8                     Longitude: 146° 47.9' W (-146.79800)


                             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 9454381 BLIGH ISLAND, T-16, AK

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