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National Ocean Service
Datums Page Page 1 of 5
Station ID: 9451936 PUBLICATION DATE: 03/04/2009
Name: PROVOROTNI ISLAND, POGIBSHI PT
AK
NOAA Chart: 17323 Latitude: 57° 30.9' N ( 57.51500)
USGS Quad: SITKA (C-5) Longitude: 135° 33.3' W (-135.55500)
To reach the tidal bench marks from Sitka, AK, proceed north through Sitka Sound
to Salisbury Sound 34 km (21 mi), then proceed NE through the Sound and Kakul
Narrows, continue north through Sergius Narrows for 19 km (12 mi) to Povorotni
Island, in southern Deadman Reach. The tidal bench marks are located on the
rock outcrop on the northern/north eastern most point of the island
approximately at 57 30.85 N; 135 33.31 W. The tide gauge was located on the
beach.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 2 1952
DESIGNATION: 945 1936 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 16672
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock OPUS PID:
LATITUDE: 57° 30.9' N ( 57.51500) LONGITUDE: 135° 33.2' W (-135.55300)
The primary bench mark is a disk set in a rock on the NE end of the island,
28.50 m (93.5 ft) north of bench mark 1936 A 2002, 21 m (69 ft) ENE of a
navigation light, 7.62 m (25.0 ft) east of bench mark NO 3 1952, and 3 m (10 ft)
in-shore from the apparent high water line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9451936 PUBLICATION DATE: 03/04/2009
Name: PROVOROTNI ISLAND, POGIBSHI PT
AK
NOAA Chart: 17323 Latitude: 57° 30.9' N ( 57.51500)
USGS Quad: SITKA (C-5) Longitude: 135° 33.3' W (-135.55500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1952
DESIGNATION: 945 1936 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 16673
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock OPUS PID:
LATITUDE: 57° 30.9' N ( 57.51500) LONGITUDE: 135° 33.2' W (-135.55300)
The bench mark is a disk set in a rock on the ridge line and foot path to
navigation light, 13 m (43 ft) from the navigation light, 11 m (36 ft) SW of the
NE end of the island, 10.36 m (34.0 ft) east of bench mark NO 4 1952, 10 m (32
ft) in-shore from the apparent high water line, and 7.62 m (25.0 ft) west of
bench mark NO 2 1952.
BENCH MARK STAMPING: NO 4 1952
DESIGNATION: 945 1936 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 16674
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock OPUS PID:
LATITUDE: 57° 30.9' N ( 57.51500) LONGITUDE: 135° 33.2' W (-135.55300)
The bench mark is a disk set in top of a jagged rock forming part of a steep
rock slope on the north end of the island, 21 m (69 ft) SW from the NE end of
the island, 10.36 m (34.0 ft) west of bench mark NO 3 1952, 6 m (20 ft) north of
navigation light, and 2 m (8 ft) in-shore from the apparent high water line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9451936 PUBLICATION DATE: 03/04/2009
Name: PROVOROTNI ISLAND, POGIBSHI PT
AK
NOAA Chart: 17323 Latitude: 57° 30.9' N ( 57.51500)
USGS Quad: SITKA (C-5) Longitude: 135° 33.3' W (-135.55500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1936 A 2002
DESIGNATION: 945 1936 A
MONUMENTATION: Tidal Station disk VM#: 16675
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock OPUS PID:
LATITUDE: 57° 30.9' N ( 57.51500) LONGITUDE: 135° 33.2' W (-135.55300)
The bench mark is a disk set flush in a large solitary rock outcrop 1 m (3 ft)
high, 29 m (95 ft) SSE from a navigation light, 28.50 m (93.5 ft) south of bench
mark NO 2 1952, 23.50 m (77.1 ft) west of bench mark 1936 B 2002, 7 m (23 ft)
from the apparent high water line, 4 m (13 ft) from the vegetation line, and 2 m
(7 ft) above the apparent high water line.
BENCH MARK STAMPING: 1936 B 2002
DESIGNATION: 945 1936 B
MONUMENTATION: Tidal Station disk VM#: 16676
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock OPUS PID:
LATITUDE: 57° 30.9' N ( 57.51500) LONGITUDE: 135° 33.2' W (-135.55300)
The bench mark is a disk set flush in a jagged rock 0.5 m x 0.5 m (1.6 ft x 1.6
ft), 23.50 m (77.1 ft) east of bench mark 1936 A 2002, SE direction from bench
mark NO 2 1952, 2.13 m (7.0 ft) from the apparent high water line and 2.13 m
(7.0 ft) above it.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9451936 PUBLICATION DATE: 03/04/2009
Name: PROVOROTNI ISLAND, POGIBSHI PT
AK
NOAA Chart: 17323 Latitude: 57° 30.9' N ( 57.51500)
USGS Quad: SITKA (C-5) Longitude: 135° 33.3' W (-135.55500)
T I D A L D A T U M S
Tidal datums at PROVOROTNI ISLAND, POGIBSHI PT based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: April 2002 - April 2002
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9451600 SITKA, BARONOF ISLAND, SITKA SOUND
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 4.614
MEAN HIGH WATER MHW = 4.316
MEAN SEA LEVEL MSL = 2.418
MEAN TIDE LEVEL MTL = 2.388
MEAN LOW WATER MLW = 0.460
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 2 1952 7.066 2.750
NO 3 1952 8.116 3.800
NO 4 1952 7.704 3.388
1936 A 2002 6.163 1.847
1936 B 2002 5.994 1.678
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9451936 PUBLICATION DATE: 03/04/2009
Name: PROVOROTNI ISLAND, POGIBSHI PT
AK
NOAA Chart: 17323 Latitude: 57° 30.9' N ( 57.51500)
USGS Quad: SITKA (C-5) Longitude: 135° 33.3' W (-135.55500)
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.