U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 04/16/1988
Station ID: 9454329 SUPERCEDED DATE: 04/21/2003
Name: CAPE HINCHINBROOK, HINCHINBROOK ENTRANCE
ALASKA
NOAA Chart: 16709 Latitude: 60° 14.4' N
USGS Quad: CORDOVA A-7 & A-8 Longitude: 146° 38.9' W
To reach the tidal bench marks, proceed to the southern tip of Hinchinbrook
Island. The bench marks are located in a wide semi-circle around the U.S. Coast
Guard (USCG) light station at Cape Hinchinbrook. The gage sensor was located to
the west of the pier and the staff was at the westernmost piling on the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 3 1972
MONUMENTATION: Survey Disk VM#: 9497
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Pylon
The bench mark is set flush in the SW corner of a 16-foot (5 m) tall concrete
pylon, 26.6 feet (8.1 m) north of a ladder that leads from the beach to the U.S.
Coast Guard light station pier.
BENCH MARK STAMPING: NO 5 1972
MONUMENTATION: Survey Disk VM#: 9498
AGENCY: PID:
SETTING CLASSIFICATION: Boulder
The bench mark is set in a low lying boulder embedded in the rocky beach, 81.6
feet (24.9 m) south of the southern support in the first group of supports at
the USCG pier.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 04/16/1988
Station ID: 9454329 SUPERCEDED DATE: 04/21/2003
Name: CAPE HINCHINBROOK, HINCHINBROOK ENTRANCE
ALASKA
NOAA Chart: 16709 Latitude: 60° 14.4' N
USGS Quad: CORDOVA A-7 & A-8 Longitude: 146° 38.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4329 G 1979
MONUMENTATION: Survey Disk VM#: 9499
AGENCY: PID:
SETTING CLASSIFICATION: Boulder
The bench mark is set in a rounded boulder protruding from the rocky shore, 73
feet (22 m) SW of the southern edge of the culvert (for a stream) under the
pier, and 18.7 feet (5.7 m) ENE of Bench Mark NO 5 1972.
BENCH MARK STAMPING: 4329 H 1984
MONUMENTATION: Survey Disk VM#: 9500
AGENCY: PID:
SETTING CLASSIFICATION: Rock
The bench mark is set in a patch of light colored rock located in the center of
a prominent moss/brush covered outcrop, about 300 feet (91 m) SW of the USCG
pier, 50 feet (15 m) north of the base of a talus slide, and 18 feet (5 m) west
of an overhanging cliff.
BENCH MARK STAMPING: 4329 I 1984
MONUMENTATION: Survey Disk VM#: 9501
AGENCY: PID:
SETTING CLASSIFICATION: Rock Ledge
The bench mark is 84.4 feet (25.7 m) NW of the NW corner of a tall concrete
pylon located on a flat portion at the base of the rock ledge, and 3 feet (1 m)
east and 3 feet (1 m) below another rock ledge which projects further seaward.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 04/16/1988
Station ID: 9454329 SUPERCEDED DATE: 04/21/2003
Name: CAPE HINCHINBROOK, HINCHINBROOK ENTRANCE
ALASKA
NOAA Chart: 16709 Latitude: 60° 14.4' N
USGS Quad: CORDOVA A-7 & A-8 Longitude: 146° 38.9' W
T I D A L D A T U M S
Tidal datums at CAPE HINCHINBROOK, HINCHINBROOK ENTRANCE based on:
LENGTH OF SERIES: 65 HW & 66 LW
TIME PERIOD: JULY 13-AUGUST 15, 1984
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 9454050 CORDOVA
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (07/30/1984) = 12.97
MEAN HIGHER HIGH WATER MHHW = 11.21
MEAN HIGH WATER MHW = 10.22
MEAN TIDE LEVEL MTL = 5.83
MEAN LOW WATER MLW = 1.44
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (07/29/1984) = -2.53
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 3 1972 22.79 12.57
NO 5 1972 19.13 8.91
4329 G 1979 20.81 10.59
4329 H 1984 24.73 14.51
4329 I 1984 21.27 11.05
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 04/16/1988
Station ID: 9454329 SUPERCEDED DATE: 04/21/2003
Name: CAPE HINCHINBROOK, HINCHINBROOK ENTRANCE
ALASKA
NOAA Chart: 16709 Latitude: 60° 14.4' N
USGS Quad: CORDOVA A-7 & A-8 Longitude: 146° 38.9' W
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 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.