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Datums Page Page 1 of 5
Station ID: 9462961 PUBLICATION DATE: 12/30/2014
Name: ISANOTSKI STRAIT ENTRANCE, IKATAN BAY
AK
NOAA Chart: 16535 Latitude: 54° 46.7' N ( 54.77844)
USGS Quad: FALSE PASS D-5 Longitude: 163° 21.9' W (-163.36428)
To reach the tidal bench marks by boat from the small boat harbor in False Pass,
proceed south approximately 9.5 km (5.1 nm) through Isanotski Strait to the day
marker at Johnson s Point in Ikatan Bay, then continue south for 0.35 km (0.2
nm) to the small reef just south of the ruins of the old trapper cabin at the
base of the bluff below Dark Mountain. The tidal bench marks are located on the
beach, the rock outcrop directly behind the small reef and the rock formation in
the flats between Ikatan Bay and Otter Cove. The tide gauge orifices are
located 100 m (373 ft) offshore and south of the small reef.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2961 A 2014
DESIGNATION: 946 2961 A
MONUMENTATION: Tidal Station disk VM#: 21175
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID#: BBDN11
LATITUDE: 54° 46.9' N ( 54.78150) LONGITUDE: 163° 21.8' W (-163.36333)
The primary bench mark is a disk set in a rock outcrop 3 m wide x 5 m long (10
ft wide x 16 ft long) that is below the high water line, 163 m (535 ft) SE of
the ruins remaining from the Johnson/Kristensen Cabin, 46 m (151 ft) ENE of the
3 m (10 ft) high sand berm, and 0.5 m (1.6 ft) above the beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9462961 PUBLICATION DATE: 12/30/2014
Name: ISANOTSKI STRAIT ENTRANCE, IKATAN BAY
AK
NOAA Chart: 16535 Latitude: 54° 46.7' N ( 54.77844)
USGS Quad: FALSE PASS D-5 Longitude: 163° 21.9' W (-163.36428)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2961 B 2014
DESIGNATION: 946 2961 B
MONUMENTATION: Tidal Station disk VM#: 21176
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 54° 46.8' N ( 54.78078) LONGITUDE: 163° 21.9' W (-163.36483)
The bench mark is a disk set in a rock outcrop 200 m (656 ft) sloped distance
SSE of ruins remaining from Johnson/Kristensen Cabin, and 75 m (246 ft) sloped
distance SW of the sand berm parallel to the beach.
BENCH MARK STAMPING: 2961 C 2014
DESIGNATION: 946 2961 C
MONUMENTATION: Tidal Station disk VM#: 21177
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 54° 46.6' N ( 54.77703) LONGITUDE: 163° 21.9' W (-163.36500)
The bench mark is a disk set in the top of a boulder 2 m x 2 m x 1 m high (6 ft
x 6 ft x 3 ft high) at the base of Dark Mountain in the flats between Ikatan Bay
and Otter Cove, 51 m (167 ft) NW of a 3 m x 1.5 m x 2.5 m high (10 ft x 5 ft x 8
ft high) boulder, and 5 m NNE of base of bluff.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9462961 PUBLICATION DATE: 12/30/2014
Name: ISANOTSKI STRAIT ENTRANCE, IKATAN BAY
AK
NOAA Chart: 16535 Latitude: 54° 46.7' N ( 54.77844)
USGS Quad: FALSE PASS D-5 Longitude: 163° 21.9' W (-163.36428)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2961 D 2014
DESIGNATION: 946 2961 D
MONUMENTATION: Tidal Station disk VM#: 21178
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 54° 46.6' N ( 54.77636) LONGITUDE: 163° 21.9' W (-163.36456)
The bench mark is a disk set in a rock outcrop at the base of Dark Mountain in
the flats between Ikatan Bay and Otter Cove, 27 m (89 ft) N of tip of N most
middle rock-outcrop fin and 1.20 m (3.9 ft) above grade.
BENCH MARK STAMPING: 2961 E 2014
DESIGNATION: 946 2961 E
MONUMENTATION: Tidal Station disk VM#: 21179
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 54° 46.5' N ( 54.77578) LONGITUDE: 163° 21.9' W (-163.36522)
The bench mark is a disk set in a rock outcrop at the base of Dark Mountain in
the flats between Ikatan Bay and Otter Cove, 57 m (187 ft) E of the SW most
rock-outcrop fin, 50 m (164 ft) SW of the N most middle rock-outcrop fin, and
0.65 m (2.1 ft) above grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9462961 PUBLICATION DATE: 12/30/2014
Name: ISANOTSKI STRAIT ENTRANCE, IKATAN BAY
AK
NOAA Chart: 16535 Latitude: 54° 46.7' N ( 54.77844)
USGS Quad: FALSE PASS D-5 Longitude: 163° 21.9' W (-163.36428)
T I D A L D A T U M S
Tidal datums at ISANOTSKI STRAIT ENTRANCE, IKATAN BAY based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: June 2014 - August 2014
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9459881 KING COVE, DEER PASSAGE, PACIFIC OCEAN
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.010
MEAN HIGH WATER MHW = 1.808
MEAN TIDE LEVEL MTL = 1.111
MEAN SEA LEVEL MSL = 1.097
MEAN LOW WATER MLW = 0.414
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2961 A 2014 2.190 0.382
2961 B 2014 15.159 13.351
2961 C 2014 5.672 3.864
2961 D 2014 5.201 3.393
2961 E 2014 5.159 3.351
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9462961 PUBLICATION DATE: 12/30/2014
Name: ISANOTSKI STRAIT ENTRANCE, IKATAN BAY
AK
NOAA Chart: 16535 Latitude: 54° 46.7' N ( 54.77844)
USGS Quad: FALSE PASS D-5 Longitude: 163° 21.9' W (-163.36428)
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.