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Bench Mark Sheet for 9450296, Custom House Cove, Mary Island 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Superseded Epoch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Small blue map location marker Unpublished bench mark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: 9450296                         PUBLICATION DATE:  07/14/2010
Name:       CUSTOM HOUSE COVE, MARY ISLAND                    
            AK
NOAA Chart: 17424                           Latitude:   55°  6.0' N (  55.10000)
USGS Quad:  KETCHIKAN A-4                   Longitude: 131° 13.0' W (-131.21700)


To reach the benchmarks by boat from Ketchikan, AK, proceed SE through Tongass
Narrows into Revillagigedo Channel, then continue ESE for 22.2 km (12.0 nm) to
Hog Rocks, then head SSE 9.3 km (5.0 nm) to Custom House Cove. Custom House Cove
is on the west side of Mary Island. The site is located on the west side of the
island, on the eastern shore of Custom House Cove immediately south of a small
rock islet.


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


                 PRIMARY BENCH MARK STAMPING:  0296 A 2010
                         DESIGNATION:          945 0296 A

MONUMENTATION:           Tidal Station disk                    VM#:        19627
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID#: BBBW71
LATITUDE:   55°  5.8' N (  55.09597)          LONGITUDE: 131° 13.3' W (-131.22211)


The primary bench mark is set flush in bedrock 43.2 m (142 ft) SSE  from the
highpoint of the prominent rock islet, 11 m (36.1 ft) seaward of the island s
wood line, 1 m (3.28 ft) above and 5 m (16.4 ft) inshore of MHW line, and 0.5 m
(1.6 ft) above the black stain on the nearby rocks.

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

                                                                                
Station ID: 9450296                         PUBLICATION DATE:  07/14/2010
Name:       CUSTOM HOUSE COVE, MARY ISLAND                    
            AK
NOAA Chart: 17424                           Latitude:   55°  6.0' N (  55.10000)
USGS Quad:  KETCHIKAN A-4                   Longitude: 131° 13.0' W (-131.21700)


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


                         BENCH MARK STAMPING:  0296 B 2010
                         DESIGNATION:          945 0296 B

MONUMENTATION:           Tidal Station disk                    VM#:        19628
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   55°  5.7' N (  55.09567)          LONGITUDE: 131° 13.3' W (-131.22186)


The bench mark is set flush in bedrock 67 m (220 ft) SSE from the highpoint of
the prominent rock islet, 23 m (75 ft) south of bench mark 945 0296 A, 4 m
(13.1ft) seaward of woodline, and 3 m (9.8 ft) above and 11 m ( 36.1 ft) inshore
of MHW line.



                         BENCH MARK STAMPING:  0296 C 2010
                         DESIGNATION:          945 0296 C

MONUMENTATION:           Tidal Station disk                    VM#:        19629
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   55°  5.7' N (  55.09536)          LONGITUDE: 131° 13.3' W (-131.22178)


The bench mark is set flush in a bedrock finger outcrop extending 6 m (19.7 ft)
seaward of tree line, 107 m (351 ft) SSE from highpoint of nearby rock islet, 72
m (237 ft) south from bench mark 945 0296 A, 42 m (138 ft) south from bench mark
945 0296 B,  5 m (16.4 ft) seaward of tree line, 2 m (6.6 ft) above and 5 m
(16.4 ft) inshore of MHW line.     

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

                                                                                
Station ID: 9450296                         PUBLICATION DATE:  07/14/2010
Name:       CUSTOM HOUSE COVE, MARY ISLAND                    
            AK
NOAA Chart: 17424                           Latitude:   55°  6.0' N (  55.10000)
USGS Quad:  KETCHIKAN A-4                   Longitude: 131° 13.0' W (-131.21700)


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


                         BENCH MARK STAMPING:  0296 D 2010
                         DESIGNATION:          945 0296 D

MONUMENTATION:           Tidal Station disk                    VM#:        19630
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Boulder                               OPUS PID:        
LATITUDE:   55°  5.7' N (  55.09494)          LONGITUDE: 131° 13.3' W (-131.22225)


The bench mark is set flush in a boulder 140 m (459 ft) south from high point of
rock islet, 121 m (396 ft) SSW from bench mark 945 0296 A, 88 m (288 ft) SSW
from bench mark 945 0296 B, 4 m (13.1 ft) seaward of a 1 m (3.3 ft) rocky ledge
in tree line, and 2 m (6.6 ft) above and 8 m (26.2 ft) inshore of MHW line. 



                         BENCH MARK STAMPING:  0296 E 2010
                         DESIGNATION:          945 0296 E

MONUMENTATION:           Tidal Station disk                    VM#:        19631
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   55°  5.7' N (  55.09472)          LONGITUDE: 131° 13.4' W (-131.22253)


The bench mark is set flush in bedrock 113 m (372 ft) SSW from bench mark 945
0296 A, 82 m (270 ft) SSW from bench mark 945 0296 C, 2 m (6.6 ft) seaward of
the tree line, and 3 m (9.8 ft) above and 10 m (32.8 ft) inshore of MHW line. 

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

                                                                                
Station ID: 9450296                         PUBLICATION DATE:  07/14/2010
Name:       CUSTOM HOUSE COVE, MARY ISLAND                    
            AK
NOAA Chart: 17424                           Latitude:   55°  6.0' N (  55.10000)
USGS Quad:  KETCHIKAN A-4                   Longitude: 131° 13.0' W (-131.21700)


                            T I D A L   D A T U M S 


Tidal datums at CUSTOM HOUSE COVE, MARY ISLAND based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           April 2010 - May 2010
     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   =  4.646
     MEAN HIGH WATER                            MHW    =  4.370
     MEAN SEA LEVEL                             MSL    =  2.428
     MEAN TIDE LEVEL                            MTL    =  2.422
     MEAN LOW WATER                             MLW    =  0.474
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     0296 A 2010                                 5.604    1.235
     0296 B 2010                                 5.148    0.778
     0296 C 2010                                 5.343    0.973
     0296 D 2010                                 5.670    1.300
     0296 E 2010                                 5.702    1.332


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

                                                                                
Station ID: 9450296                         PUBLICATION DATE:  07/14/2010
Name:       CUSTOM HOUSE COVE, MARY ISLAND                    
            AK
NOAA Chart: 17424                           Latitude:   55°  6.0' N (  55.10000)
USGS Quad:  KETCHIKAN A-4                   Longitude: 131° 13.0' W (-131.21700)


                             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 9450296 Custom House Cove, Mary Island, AK

Revised: 10/15/2013
NOAA / National Ocean Service
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