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Bench Mark Sheet for 9450753, Magnetic Point, Union Bay, Earnest Sound 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 9450753                         PUBLICATION DATE:  08/06/2009
Name:       MAGNETIC POINT, UNION BAY, ERNEST SOUND           
            AK
NOAA Chart: 17423                           Latitude:   55° 47.3' N (  55.78828)
USGS Quad:  CRAIG (D-1)                     Longitude: 132° 11.5' W (-132.19088)


To reach the Magnetic Point tidal benchmarks, travel to the eastern shore of
Ernest Sound south of Union Point and north of Magnetic Point within Union Bay;
in the NE portion of Union Bay there are two islands; on the east shore of Union
Bay, proceed about 0.6 km (0.4 mi) north along the west shore of Magnetic Point,
east of a small island, in the northerly of two rock outcroppings both topped by
moss and stunted trees.  Specifically, the tidal bench marks are located on the
eastern shore due east of the southern island.  The bench marks are on private
property that consists of densely wooded area surrounding intertidal grassland
protected by two rock ledge peninsulas. The staff was positioned on a flat faced
rock wall facing west located on a west facing rock ledge.


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


                 PRIMARY BENCH MARK STAMPING:  0753 A 2009
                         DESIGNATION:          945 0753 A

MONUMENTATION:           Tidal Station disk                    VM#:        19229
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock ledge                            OPUS PID:        
LATITUDE:   55° 47.3' N (  55.78827)          LONGITUDE: 132° 11.5' W (-132.19085)


The primary bench mark is a disk set flush on a rock ledge just in front of the
intertidal zone, located on the shore facing the west. 

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

                                                                                
Station ID: 9450753                         PUBLICATION DATE:  08/06/2009
Name:       MAGNETIC POINT, UNION BAY, ERNEST SOUND           
            AK
NOAA Chart: 17423                           Latitude:   55° 47.3' N (  55.78828)
USGS Quad:  CRAIG (D-1)                     Longitude: 132° 11.5' W (-132.19088)


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


                         BENCH MARK STAMPING:  0753 B 2009
                         DESIGNATION:          945 0753 B

MONUMENTATION:           Tidal Station disk                    VM#:        19230
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Inshore edge                          OPUS PID:        
LATITUDE:   55° 47.3' N (  55.78805)          LONGITUDE: 132° 11.4' W (-132.19073)


The bench mark is a disk located on the southern inshore edge of the forest and
the intertidal zone. 



                         BENCH MARK STAMPING:  0753 C 2009
                         DESIGNATION:          945 0753 C

MONUMENTATION:           Tidal Station disk                    VM#:        19231
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Inshore edge                          OPUS PID:        
LATITUDE:   55° 47.3' N (  55.78838)          LONGITUDE: 132° 11.4' W (-132.19053)


The bench mark is a disk located on the northern inshore edge of the forest and
intertidal zone.

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

                                                                                
Station ID: 9450753                         PUBLICATION DATE:  08/06/2009
Name:       MAGNETIC POINT, UNION BAY, ERNEST SOUND           
            AK
NOAA Chart: 17423                           Latitude:   55° 47.3' N (  55.78828)
USGS Quad:  CRAIG (D-1)                     Longitude: 132° 11.5' W (-132.19088)


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


                         BENCH MARK STAMPING:  0753 D 2009
                         DESIGNATION:          945 0753 D

MONUMENTATION:           Tidal Station disk                    VM#:        19232
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   55° 47.3' N (  55.78865)          LONGITUDE: 132° 11.4' W (-132.19072)


The bench mark is a disk set flush into bedrock north of the intertidal zone,
and located on the shore facing west. 



                         BENCH MARK STAMPING:  0753 E 2009
                         DESIGNATION:          945 0753 E

MONUMENTATION:           Tidal Station disk                    VM#:        19233
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock ledge                            OPUS PID:        
LATITUDE:   55° 47.3' N (  55.78798)          LONGITUDE: 132° 11.5' W (-132.19105)


The bench mark is a disk set flush into bedrock horizontally south of the
intertidal zone, and located on a rock ledge that faces the west. 

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

                                                                                
Station ID: 9450753                         PUBLICATION DATE:  08/06/2009
Name:       MAGNETIC POINT, UNION BAY, ERNEST SOUND           
            AK
NOAA Chart: 17423                           Latitude:   55° 47.3' N (  55.78828)
USGS Quad:  CRAIG (D-1)                     Longitude: 132° 11.5' W (-132.19088)


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


                         BENCH MARK STAMPING:  VIXEN HBR 2009
                         DESIGNATION:          VIXEN HBR 2009

MONUMENTATION:           Tidal Station disk                    VM#:        19234
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Solid rock                            OPUS PID#: BBBK46
LATITUDE:   55° 47.3' N (  55.78840)          LONGITUDE: 132° 11.5' W (-132.19085)


The bench mark is a disk set in a solid rock, at the South end of the mossy cap,
about 1.83 m (6.0 ft) south of a dwarf hemlock, and approximately 0.9 m (3 ft)
above high water.

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

                                                                                
Station ID: 9450753                         PUBLICATION DATE:  08/06/2009
Name:       MAGNETIC POINT, UNION BAY, ERNEST SOUND           
            AK
NOAA Chart: 17423                           Latitude:   55° 47.3' N (  55.78828)
USGS Quad:  CRAIG (D-1)                     Longitude: 132° 11.5' W (-132.19088)


                            T I D A L   D A T U M S 


Tidal datums at MAGNETIC POINT, UNION BAY, ERNEST SOUND based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           May 2009 - May 2009
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9450460 KETCHIKAN, TONGASS NARROWS


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

     MEAN HIGHER HIGH WATER                     MHHW   =  4.888
     MEAN HIGH WATER                            MHW    =  4.617
     MEAN TIDE LEVEL                            MTL    =  2.546
     MEAN SEA LEVEL                             MSL    =  2.539
     MEAN LOW WATER                             MLW    =  0.476
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     0753 A 2009                                 7.013    2.396
     0753 B 2009                                 6.274    1.657
     0753 C 2009                                 6.463    1.846
     0753 D 2009                                 5.232    0.616
     0753 E 2009                                 5.769    1.152
     VIXEN HBR 2009                              7.008    2.391


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

                                                                                
Station ID: 9450753                         PUBLICATION DATE:  08/06/2009
Name:       MAGNETIC POINT, UNION BAY, ERNEST SOUND           
            AK
NOAA Chart: 17423                           Latitude:   55° 47.3' N (  55.78828)
USGS Quad:  CRAIG (D-1)                     Longitude: 132° 11.5' W (-132.19088)


                             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 9450753 Magnetic Point, Union Bay, Earnest Sound, AK

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