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National Ocean Service
Datums Page Page 1 of 5
Station ID: 9462723 PUBLICATION DATE: 12/20/2012
Name: ROOTOK ISLAND, ROOTOK STRAIT
AK
NOAA Chart: 16531 Latitude: 54° 3.1' N ( 54.05222)
USGS Quad: UNIMAK A-5 Longitude: 165° 30.9' W (-165.51417)
To reach the tidal benchmarks from the small boat harbor in Dutch Harbor proceed
by boat NE for 59.3 km (32.0 nm) to the north side of Akutan Island, then
proceed SE for 42.1 km (22.8 nm) through Akun Strait and into Rootok Strait,
then SW for 1.6 km (0.9 nm) into an unnamed bay on the NE side of Rootok Island.
The benchmarks are located along the beach north of the southern most creek
which runs into the unnamed bay over a sand beach. The tide house is located on
the southern most rock peninsula north of the creek.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2723 B 2012
DESIGNATION: 946 2723 B
MONUMENTATION: Tidal Station disk VM#: 20557
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID#: BBCT67
LATITUDE: 54° 3.1' N ( 54.05220) LONGITUDE: 165° 30.8' W (-165.51398)
The primary bench mark is a disk set near the center of the second large bedrock
outcrop which is surrounded by water at high tide and north of a creek and sand
beach in an unnamed bay on the NE side of Rootok Island, 101.9 m (334 ft) SE of
bench mark 946 2723 C, 89.35 m (293.1 ft) NNE of bench mark 946 2723 A, 7.05 m
(23.1 ft) ENE of the high point of the western extent of the rock outcrop, 3.39
m (11.1 ft) WSW of the highest point of the rock outcrop, 1.70 m (5.6 ft) SE of
the NW rock outcrop cliff edge, 0.80 m (2.6 ft) NW of the SE cliff edge, and 4.5
m (15 ft) above the beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9462723 PUBLICATION DATE: 12/20/2012
Name: ROOTOK ISLAND, ROOTOK STRAIT
AK
NOAA Chart: 16531 Latitude: 54° 3.1' N ( 54.05222)
USGS Quad: UNIMAK A-5 Longitude: 165° 30.9' W (-165.51417)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2723 A 2012
DESIGNATION: 946 2723 A
MONUMENTATION: Tidal Station disk VM#: 20558
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 54° 3.1' N ( 54.05148) LONGITUDE: 165° 30.9' W (-165.51459)
The bench mark is a disk set in a bedrock outcrop at the base of the bluff above
the sand beach and north of the creek in an unnamed bay on the NE side of Rootok
Island, 89.35 m (293.1 ft) SSW of bench mark 946 2723 B, 9.49 m (31.1 ft) NNW
of the NE corner of the first large boulder north of the creek, 6.11 m (20.0 ft)
south from the NE most point of the second rock outcrop at the base of the
bluff, 0.51 m (1.7 ft) ENE from the rock bluff, and 0.39 m (1.3 ft) above the
beach.
BENCH MARK STAMPING: 2723 C 2012
DESIGNATION: 946 2723 C
MONUMENTATION: Tidal Station disk VM#: 20559
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 54° 3.2' N ( 54.05285) LONGITUDE: 165° 30.9' W (-165.51508)
The bench mark is a disk set in a 1.2 m (4 ft) wide bedrock outcrop at the base
of a bluff above a rock beach in an unnamed bay on the NE side of Rootok Island,
116.8 m (383 ft) south of bench mark 946 2723 D, 101.9 m (334 ft) NW of bench
mark 946 2723 B, 5.05 m (16.6 ft) SSE from the highest point on a boulder (1m x
2m x 1.5m) at the end of a rock slide, 1.15 m (3.8 ft) SW of the NE edge of the
ledge which drops down to the beach, 0.17 m (0.6 ft) NE of the rock wall nearest
to the bench mark, and 1.30 m (4.3 ft) above the beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9462723 PUBLICATION DATE: 12/20/2012
Name: ROOTOK ISLAND, ROOTOK STRAIT
AK
NOAA Chart: 16531 Latitude: 54° 3.1' N ( 54.05222)
USGS Quad: UNIMAK A-5 Longitude: 165° 30.9' W (-165.51417)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2723 D 2012
DESIGNATION: 946 2723 D
MONUMENTATION: Tidal Station disk VM#: 20560
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 54° 3.2' N ( 54.05388) LONGITUDE: 165° 30.9' W (-165.51541)
The bench mark is a disk set in a 1.6 m (5 ft) wide by 7.5 m (21 ft) long low
grey and black rock outcrop on a rock beach in an unnamed bay on the NE side of
Rootok Island, 116.8 m (383 ft) N of bench mark 946 2723 C, 65.05 m (213.4 ft)
SE of bench mark 946 2723 E, 6.09 m (20.0 ft) SE of a 12 m (39 ft) high pointed
rock wall, 6.00 m (19.7 ft) NE of the rock bluff at the top of the beach, 4.93 m
(16.2 ft) NE of the inland end of the rock outcrop, 1.62 m (2.0 ft) WSW of the
seaward end of the rock outcrop, and 0.52 m (0.7 ft) above the rock beach.
BENCH MARK STAMPING: 2723 E 2012
DESIGNATION: 946 2723 E
MONUMENTATION: Tidal Station disk VM#: 20561
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 54° 3.3' N ( 54.05434) LONGITUDE: 165° 31.0' W (-165.51602)
The bench mark is a disk set in the base of a rock outcrop that rises
approximately 5 m (16 ft) above the rock beach with grassy tufts on top in an
unnamed bay on the NE side of Rootok Island, 65.05 m (213.4 ft) NW of bench mark
946 2723 D, 58.45 m (191.8 ft) NW of a 12 m (39 ft) high pointed rock wall,
5.50 m (18.0 ft) SSW of the apparent mean high water line, 2.81 m (9.2 ft) SSW
of the seaward end of the outcrop, and 0.80 m (2.6 ft) above the rock beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9462723 PUBLICATION DATE: 12/20/2012
Name: ROOTOK ISLAND, ROOTOK STRAIT
AK
NOAA Chart: 16531 Latitude: 54° 3.1' N ( 54.05222)
USGS Quad: UNIMAK A-5 Longitude: 165° 30.9' W (-165.51417)
T I D A L D A T U M S
Tidal datums at ROOTOK ISLAND, ROOTOK STRAIT based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: July 2012 - July 2012
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 = 1.543
MEAN HIGH WATER MHW = 1.374
MEAN TIDE LEVEL MTL = 0.874
MEAN SEA LEVEL MSL = 0.864
MEAN LOW WATER MLW = 0.374
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2723 B 2012 4.377 3.003
2723 A 2012 4.558 3.184
2723 C 2012 4.078 2.704
2723 D 2012 2.184 0.811
2723 E 2012 3.179 1.805
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9462723 PUBLICATION DATE: 12/20/2012
Name: ROOTOK ISLAND, ROOTOK STRAIT
AK
NOAA Chart: 16531 Latitude: 54° 3.1' N ( 54.05222)
USGS Quad: UNIMAK A-5 Longitude: 165° 30.9' W (-165.51417)
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.