U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 4
Station ID: 9457313 PUBLICATION DATE: 05/16/2025
Name: PORT WILLIAM, SHUYAK ISLAND
AK
NOAA Chart: US5AK6YX Latitude: 58° 29.4' N ( 58.49022)
USGS Quad: AFOGNAK B-2 NW Longitude: 152° 35.0' W (-152.58377)
To reach the tide station from Lilly Lake Seaplane Base in Kodiak by floatplane
proceed north for 77.6 km (48.2 mi) to the Port William Lodge. The station is on
the pier and the benchmarks are on the coast east and west of the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO. 1 1971
DESIGNATION: 945 7313 Tidal 1
MONUMENTATION: Tidal Station disk VM#: 25044
AGENCY: USCGS IDB PID#:
SETTING CLASSIFICATION: rock outcrop OPUS PID:
LATITUDE: 58° 29.4' N ( 58.49067) LONGITUDE: 152° 35.0' W (-152.58264)
The mark is a standard 3.5-inch brass USCGS disk set in bedrock, 83.5 m (273.9
ft) NE of a davit crane on the south face of the cannery dock, 10.7 m (35.1 ft)
west of a large rock that used to be banded with a steel cable, 4.6 m (15.1 ft)
north of the high water line.
BENCH MARK STAMPING: NO. 2 1971
DESIGNATION: 945 7313 Tidal 2
MONUMENTATION: Tidal Station disk VM#: 25045
AGENCY: USCGS IDB PID#:
SETTING CLASSIFICATION: rock outcrop OPUS PID#: BBJS22
LATITUDE: 58° 29.4' N ( 58.49070) LONGITUDE: 152° 34.9' W (-152.58228)
The bench mark is a 3.5-inch brass USCGS disk set in bedrock, 98.1 m (321.8 ft)
NE of a davit crane on the south face of the cannery dock, 22.4 m (73.5 ft) SW
of bench mark 945 7313 Tidal 3, 19.8 m (65.0 ft) east of bench mark 945 7313
Tidal 1, and 7.6 m (24.9 ft) east of a large rock that used to be banded with a
steel cable.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 9457313 PUBLICATION DATE: 05/16/2025
Name: PORT WILLIAM, SHUYAK ISLAND
AK
NOAA Chart: US5AK6YX Latitude: 58° 29.4' N ( 58.49022)
USGS Quad: AFOGNAK B-2 NW Longitude: 152° 35.0' W (-152.58377)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7313 A 2024
DESIGNATION: 945 7313 A
MONUMENTATION: Tidal Station disk VM#: 25049
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: structure on bedrock OPUS PID:
LATITUDE: 58° 29.4' N ( 58.49072) LONGITUDE: 152° 35.1' W (-152.58417)
The mark is a 3.5-inch brass disk set in concrete foundation sitting directly on
bedrock, 87 m (285.4 ft) west of bench mark 945 7313 Tidal 1, 14.6 m (47.9 ft)
ESE of a 3-way intersection of the boardwalk, 0.47 m (1.5 ft) north of the edge
of concrete.
BENCH MARK STAMPING: 7313 B 2024
DESIGNATION: 945 7313 B
MONUMENTATION: Tidal Station disk VM#: 25053
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: unspecified rock OPUS PID#: BBJS14
LATITUDE: 58° 29.4' N ( 58.49055) LONGITUDE: 152° 35.2' W (-152.58633)
The mark is a standard 3.5-inch brass disk set in a 1.39 m (4.6 ft) by 0.81 m
(2.7 ft) wide and 0.41 m (1.3 ft) tall granite boulder embedded in the beach
just west of the cannery buildings, 128.1 m (420.3 ft) NW of the SW-most piling
of the cannery dock, 99.8 m (327.4 ft) WSW of the SW corner of a log shed
referred to as the fish shack, 28.6 m (93.8 ft) WNW of a brown pyramidal rock
which measures 2.23 m (7.3 ft) by 1.36 m (4.5 ft) wide by 1.12 m (3.7 ft) tall,
and 7.8 m (25.6 ft) SE of a cliff face. The disk is set flush in the rock and
0.41 m (1.3 ft) above the surrounding ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 9457313 PUBLICATION DATE: 05/16/2025
Name: PORT WILLIAM, SHUYAK ISLAND
AK
NOAA Chart: US5AK6YX Latitude: 58° 29.4' N ( 58.49022)
USGS Quad: AFOGNAK B-2 NW Longitude: 152° 35.0' W (-152.58377)
T I D A L D A T U M S
Tidal datums at PORT WILLIAM, SHUYAK ISLAND based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: May 2024 - July 2024
TIDAL EPOCH: 2012-2016
CONTROL TIDE STATION: 9455500 SELDOVIA, COOK INLET
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 4.246
MEAN HIGH WATER MHW = 3.980
MEAN TIDE LEVEL MTL = 2.236
MEAN SEA LEVEL MSL = 2.236
North American Vertical Datum NAVD88 = 0.929
MEAN LOW WATER MLW = 0.492
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO. 1 1971 5.692 1.712
NO. 2 1971 4.307 0.327
7313 A 2024 5.980 2.000
7313 B 2024 4.069 0.089
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 9457313 PUBLICATION DATE: 05/16/2025
Name: PORT WILLIAM, SHUYAK ISLAND
AK
NOAA Chart: US5AK6YX Latitude: 58° 29.4' N ( 58.49022)
USGS Quad: AFOGNAK B-2 NW Longitude: 152° 35.0' W (-152.58377)
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.