U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
Station ID: 9454907 PUBLICATION DATE: 06/20/2011
Name: BLACKSTONE BAY, PR. WILLIAM SOUND
AK
NOAA Chart: 16705 Latitude: 60° 45.9' N ( 60.76500)
USGS Quad: Seward C-5 Longitude: 148° 31.4' W (-148.52300)
To reach tidal bench marks, follow the entrance of Blackstone Bay until
approximately 5.50 m (18.0 ft) SW of Point Pigot. The bench mark is located on
the SE shore of Blackstone Bay on the point where the general trend of the
shoreline changes from east-west to northeast-southwest.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: ZIRCON 1948
MONUMENTATION: Triangulation Station disk VM#: 14712
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: UW7355
SETTING CLASSIFICATION: Rock bluff OPUS PID#: UW7355
LATITUDE: 60° 45.9' N ( 60.76500) LONGITUDE: 148° 31.4' W (-148.52300)
The primary bench mark is a disk located on top of a grass covered rock bluff
4.0 m (13.1 ft) above the approximate high water line, about 300.0 m (984.2 ft)
NE of a small island, 25 m (82 ft) SW (200 magnetic) from bench mark 4907 A
1995.
BENCH MARK STAMPING: 4907 A 1995
MONUMENTATION: Survey disk VM#: 14709
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rocky outcrop OPUS PID:
LATITUDE: 60° 45.9' N ( 60.76500) LONGITUDE: 148° 31.4' W (-148.52300)
The bench mark is a disk situated on a rocky outcrop with a sheer vertical face
which faces the west, 25 m (82 ft) SW (200 magnetic) from bench mark ZIRCON
1948, and 3.0 m (9.8 ft) seaward of the treeline.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 9454907 PUBLICATION DATE: 06/20/2011
Name: BLACKSTONE BAY, PR. WILLIAM SOUND
AK
NOAA Chart: 16705 Latitude: 60° 45.9' N ( 60.76500)
USGS Quad: Seward C-5 Longitude: 148° 31.4' W (-148.52300)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4907 B 1995
MONUMENTATION: Survey disk VM#: 14710
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Flat piece of stepped bedrock OPUS PID:
LATITUDE: 60° 45.9' N ( 60.76500) LONGITUDE: 148° 31.4' W (-148.52300)
The bench mark is a disk set on a flat piece of stepped bedrock, 25.0 m (82.0
ft) east (090 magnetic) from bench mark ZIRCON Reference, and 15.0 m (49.2 ft)
SW (240 magnetic) from bench mark 4907 C 1995.
BENCH MARK STAMPING: 4907 C 1995
MONUMENTATION: Survey disk VM#: 14711
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rocky outcrop bluff OPUS PID:
LATITUDE: 60° 45.9' N ( 60.76500) LONGITUDE: 148° 31.4' W (-148.52300)
The bench mark is a disk set on a rocky outcrop bluff along the north side of a
small cut in the shoreline, and bears SE 160 magnetic compass from bench mark
4907 B 1995.
BENCH MARK STAMPING: ZIRCON Reference
MONUMENTATION: Triangulation Station disk VM#: 14713
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AH7456
SETTING CLASSIFICATION: Rock OPUS PID#:
LATITUDE: 60° 45.9' N ( 60.76500) LONGITUDE: 148° 31.4' W (-148.52300)
The bench mark is a disk set on top of a bare rock about 3.0 m (9.8 ft) above
the approximate high water line, set approximately 1.0 m (3.3 ft) back from
seaward edge of he rock, and 15.0 m (49.2 ft) NE (070 magnetic) from bench mark
4907 B 1995.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 9454907 PUBLICATION DATE: 06/20/2011
Name: BLACKSTONE BAY, PR. WILLIAM SOUND
AK
NOAA Chart: 16705 Latitude: 60° 45.9' N ( 60.76500)
USGS Quad: Seward C-5 Longitude: 148° 31.4' W (-148.52300)
T I D A L D A T U M S
Tidal datums at BLACKSTONE BAY, PR. WILLIAM SOUND based on:
LENGTH OF SERIES: 32 DAYS
TIME PERIOD: September 10 1995 - October 11 1995
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9454240 VALDEZ, PRINCE WILLIAM SOUND
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.696
MEAN HIGH WATER MHW = 3.419
MEAN SEA LEVEL MSL = 1.977
MEAN TIDE LEVEL MTL = 1.937
MEAN LOW WATER MLW = 0.455
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
ZIRCON 1948 6.801 3.382
4907 A 1995 5.673 2.254
4907 B 1995 7.605 4.186
4907 C 1995 5.975 2.556
ZIRCON Reference 6.637 3.218
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 9454907 PUBLICATION DATE: 06/20/2011
Name: BLACKSTONE BAY, PR. WILLIAM SOUND
AK
NOAA Chart: 16705 Latitude: 60° 45.9' N ( 60.76500)
USGS Quad: Seward C-5 Longitude: 148° 31.4' W (-148.52300)
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.