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National Ocean Service
Datums Page Page 1 of 5
Station ID: 9462662 PUBLICATION DATE: 06/14/2010
Name: REEF BIGHT
AK
NOAA Chart: 16520 Latitude: 54° 7.8' N ( 54.13072)
USGS Quad: UNALASKA (D-1) Longitude: 166° 6.0' W (-166.09933)
To reach the tidal bench marks by boat from the city dock in Dutch Harbor,
proceed NNE 12 km (6.4 nm) to Priest Rock, turn right and proceed NE 26.8 km
(14.3 nm) across Akutan Pass to Reef Bight on Akutan Island and a boulder beach
with three waterfalls. The bench marks are along the shore just above the high
water line between the two northern falls.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2662 A 2007
DESIGNATION: 946 2662 A
MONUMENTATION: Tidal Station disk VM#: 18580
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Top of a Boulder OPUS PID#: BBBG33
LATITUDE: 54° 7.9' N ( 54.13170) LONGITUDE: 166° 6.0' W (-166.10000)
The primary bench mark is a disk set flush on top of a boulder 3.8 m x 3.6 m x
1.6 m (12 ft x 12 ft x 5 ft) high, 89 m (290 ft) SSW from the farthest north
waterfall, 40.39 m (132.5 ft) north from tidal bench mark 946 2662 B, 7.6 m (25
ft) ESE from apparent MHW, and 7.0 m (23 ft) west from the base of the bluff.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9462662 PUBLICATION DATE: 06/14/2010
Name: REEF BIGHT
AK
NOAA Chart: 16520 Latitude: 54° 7.8' N ( 54.13072)
USGS Quad: UNALASKA (D-1) Longitude: 166° 6.0' W (-166.09933)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2662 B 2007
DESIGNATION: 946 2662 B
MONUMENTATION: Tidal Station disk VM#: 18581
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Top of a Boulder OPUS PID:
LATITUDE: 54° 7.8' N ( 54.13000) LONGITUDE: 166° 6.0' W (-166.10000)
The bench mark is a disk set flush on top of a boulder 3 m x 2 m x 1 m (10 ft x
7 ft x 3 ft) high, 71.14 m (233.4 ft) north from tidal bench mark 946 2662 C,
40.39 m (132.5 ft) south from tidal bench mark 946 2662 A, 11.9 m (39 ft) west
from the base of bluff and vegetation, and 5.80 m (19.0 ft) east from apparent
MHW.
BENCH MARK STAMPING: 2662 C 2007
DESIGNATION: 946 2662 C
MONUMENTATION: Tidal Station disk VM#: 18582
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Top of a Boulder OPUS PID:
LATITUDE: 54° 7.8' N ( 54.13000) LONGITUDE: 166° 6.0' W (-166.10000)
The bench mark is a disk set flush on top of a boulder 2 m x 1.1 m x 0.38 m (6
ft x 3.6 ft x 1.3 ft) high, 71.14 m (233.4 ft) south from tidal bench mark 946
2662 B, 53.50 m (175.5 ft) NNE from tidal bench mark 946 2662 D, 6.4 m (21 ft)
west from the base of bluff and vegetation, and 5.7 m (19 ft) east from apparent
MHW.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9462662 PUBLICATION DATE: 06/14/2010
Name: REEF BIGHT
AK
NOAA Chart: 16520 Latitude: 54° 7.8' N ( 54.13072)
USGS Quad: UNALASKA (D-1) Longitude: 166° 6.0' W (-166.09933)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2662 D 2007
DESIGNATION: 946 2662 D
MONUMENTATION: Tidal Station disk VM#: 18583
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Top of a Boulder OPUS PID:
LATITUDE: 54° 7.8' N ( 54.13000) LONGITUDE: 166° 6.0' W (-166.10000)
The bench mark is a disk set flush on top of a boulder 2.2 m x 1.5 m x 1 m (7 ft
x 5 ft x 3 ft) high, 56.55 m (185.5 ft) north from 946 2662 E, 53.50 m (175.5
ft) SSW from 946 2662 C, 14.0 m (46 ft) west from the base of the bluff, and 4.6
m (15 ft) east from apparent MHW.
BENCH MARK STAMPING: 2662 E 2007
DESIGNATION: 946 2662 E
MONUMENTATION: Tidal Station disk VM#: 18584
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Top of a Boulder OPUS PID:
LATITUDE: 54° 7.7' N ( 54.12830) LONGITUDE: 166° 6.0' W (-166.10000)
The bench mark is a disk set flush on a boulder 2.8 m x 2.1 m x 2.3 m (9 ft x 7
ft x 8 ft) high, 56.55 m (185.5 ft) south from 946 2662 D, 11.7 m (38 ft) west
from base of bluff, 6.7 m (22 ft) east from apparent MHW, and 2.3 m (8 ft) west
from vegetation.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9462662 PUBLICATION DATE: 06/14/2010
Name: REEF BIGHT
AK
NOAA Chart: 16520 Latitude: 54° 7.8' N ( 54.13072)
USGS Quad: UNALASKA (D-1) Longitude: 166° 6.0' W (-166.09933)
T I D A L D A T U M S
Tidal datums at REEF BIGHT based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: June 2007 - July 2007
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9462620 UNALASKA, DUTCH HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 1.098
MEAN HIGH WATER MHW = 1.008
MEAN TIDE LEVEL MTL = 0.652
MEAN SEA LEVEL MSL = 0.614
MEAN LOW WATER MLW = 0.296
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2662 A 2007 4.728 3.720
2662 B 2007 2.726 1.718
2662 C 2007 3.223 2.215
2662 D 2007 2.623 1.615
2662 E 2007 3.842 2.834
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9462662 PUBLICATION DATE: 06/14/2010
Name: REEF BIGHT
AK
NOAA Chart: 16520 Latitude: 54° 7.8' N ( 54.13072)
USGS Quad: UNALASKA (D-1) Longitude: 166° 6.0' W (-166.09933)
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.