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Bench Mark Sheet for 9452368, SWANSON HARBOR 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 9452368                         PUBLICATION DATE:  06/18/2014
Name:       SWANSON HARBOR                                    
            AK
NOAA Chart: 17316                           Latitude:   58° 12.9' N (  58.21500)
USGS Quad:  JUNEAU A-4                      Longitude: 135°  7.6' W (-135.12700)


To reach the tidal bench marks from the town of Gustavus, Icy Passage, proceed
by boat SE along Icy Strait for about 43 km (23 nm) to the junction of Icy
Strait and Lynn Canal, then north to the entrance to Swanson Harbor.  The bench
marks are on Ansley Island, mostly on the east coast.  The tide gage and staff
were on the SE coast of the island.


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


                 PRIMARY BENCH MARK STAMPING:  4 1959
                         DESIGNATION:          945 2368 TIDAL 4

MONUMENTATION:           Tidal Station disk                    VM#:         9430
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   58° 12.0' N (  58.20000)          LONGITUDE: 135°  6.5' W (-135.10800)


The primary bench mark is a disk set in a large granite outcrop on the east side
of the island, north of the rocky point of the beach, about 366 m (1200 ft)
north of the cliff that bench mark 945 2368 BOLT is set in, and near the
apparent high water line.

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

                                                                                
Station ID: 9452368                         PUBLICATION DATE:  06/18/2014
Name:       SWANSON HARBOR                                    
            AK
NOAA Chart: 17316                           Latitude:   58° 12.9' N (  58.21500)
USGS Quad:  JUNEAU A-4                      Longitude: 135°  7.6' W (-135.12700)


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


                         BENCH MARK STAMPING:  3 1959
                         DESIGNATION:          945 2368 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:         9429
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   58° 12.3' N (  58.20500)          LONGITUDE: 135°  6.5' W (-135.10800)


The bench mark is a disk set in a slightly sloping surface formed at the bottom
of a chain-shaped rock, on the east side of the first rocky point south of the
north end of the island, and near the apparent high water line.



                         BENCH MARK STAMPING:  2368 A 1986
                         DESIGNATION:          945 2368 A

MONUMENTATION:           Tidal Station disk                    VM#:         9431
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   58° 12.0' N (  58.20000)          LONGITUDE: 135°  6.5' W (-135.10800)


The bench mark is a disk set in bedrock on the east side of the island, at the
base of the south edge of a large crack in the third rocky bluff, 290 m (950 ft)
SE of bench mark 945 2368 BOLT, and near the apparent high water line.



                         BENCH MARK STAMPING:  SWANSON 1987

MONUMENTATION:           Tidal Station disk                    VM#:         9433
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock boulder                          OPUS PID:        
LATITUDE:   58° 12.0' N (  58.20000)          LONGITUDE: 135°  6.5' W (-135.10800)


The bench mark is a disk set between bench marks 2368 A 1986 and 2368 B 1986 in
a large flat-topped boulder among a group of the largest boulders on a foul
shoreline covered with sharp jagged boulders.

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

                                                                                
Station ID: 9452368                         PUBLICATION DATE:  06/18/2014
Name:       SWANSON HARBOR                                    
            AK
NOAA Chart: 17316                           Latitude:   58° 12.9' N (  58.21500)
USGS Quad:  JUNEAU A-4                      Longitude: 135°  7.6' W (-135.12700)


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


                         BENCH MARK STAMPING:   
                         DESIGNATION:          945 2368 BOLT
                         ALIAS:                NO STAMPING 1

MONUMENTATION:           Bolt                                  VM#:         9434
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   58° 12.0' N (  58.20000)          LONGITUDE: 135°  6.5' W (-135.10800)


The bench mark is a cross cut in a copper bolt set in the face of a bluff on the
east side of the island, about halfway between the northern and southern tips,
and 6 m (20 ft) SE of a recess in the bluff resembling a cave.

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

                                                                                
Station ID: 9452368                         PUBLICATION DATE:  06/18/2014
Name:       SWANSON HARBOR                                    
            AK
NOAA Chart: 17316                           Latitude:   58° 12.9' N (  58.21500)
USGS Quad:  JUNEAU A-4                      Longitude: 135°  7.6' W (-135.12700)


                            T I D A L   D A T U M S 


Tidal datums at SWANSON HARBOR based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           October 1986 - October 1986
     TIDAL EPOCH:           2007-2011
     CONTROL TIDE STATION:  9452210 JUNEAU, GASTINEAU CHANNEL, STEPHENS PASS


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

     MEAN HIGHER HIGH WATER                     MHHW   =  4.662
     MEAN HIGH WATER                            MHW    =  4.352
     MEAN SEA LEVEL                             MSL    =  2.445
     MEAN TIDE LEVEL                            MTL    =  2.417
     MEAN LOW WATER                             MLW    =  0.482
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     4 1959                                      7.363    3.011
     3 1959                                      5.195    0.843
     2368 A 1986                                 5.987    1.635
     SWANSON 1987                                7.129    2.777
     945 2368 BOLT                               7.540    3.188


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

                                                                                
Station ID: 9452368                         PUBLICATION DATE:  06/18/2014
Name:       SWANSON HARBOR                                    
            AK
NOAA Chart: 17316                           Latitude:   58° 12.9' N (  58.21500)
USGS Quad:  JUNEAU A-4                      Longitude: 135°  7.6' W (-135.12700)


                             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 9452368 SWANSON HARBOR, AK

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