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Datums Page Page 1 of 6
Station ID: 9459163 PUBLICATION DATE: 10/30/2009
Name: HERENDEEN ISLAND, SHUMAGIN ISLANDS
AK
NOAA Chart: 16556 Latitude: 55° 3.9' N ( 55.06556)
USGS Quad: STEPOVAK BAY (1963) Longitude: 159° 25.1' W (-159.41867)
Herendeen Island is located directly north of Little Koniuji Island; the two are
separated by Northwest Harbor. All five(5) newly installed bench marks and the
newly stalled HORCON benchmark are in close proximity to the shoreline and lie
below a grass-covered ledge which parallels the shoreline. The tidal benchmarks
span a linear region of approximately 250 meters (820 feet), beginning with
9459163A 2009 in the north and ending with 9459163E 2009 at the southernmost
extent. The Herendeen Island tide gauge (#945-9163) is located on the southwest
facing shore of Herendeen Island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9163 A 2009
DESIGNATION: 945 9163 A
MONUMENTATION: Tidal Station disk VM#: 19286
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Granite bedrock OPUS PID:
LATITUDE: 55° 4.1' N ( 55.06786) LONGITUDE: 159° 25.3' W (-159.42217)
The primary bench mark is a disk set fluch into granite bedrock at the base of a
rock ledge, located at the NW extent of a grassy recess in the bedrock and 7 m
(23 ft) inshore at apparent high water.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 9459163 PUBLICATION DATE: 10/30/2009
Name: HERENDEEN ISLAND, SHUMAGIN ISLANDS
AK
NOAA Chart: 16556 Latitude: 55° 3.9' N ( 55.06556)
USGS Quad: STEPOVAK BAY (1963) Longitude: 159° 25.1' W (-159.41867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9163 B 2009
DESIGNATION: 945 9163 B
MONUMENTATION: Tidal Station disk VM#: 19287
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Granite boulder OPUS PID:
LATITUDE: 55° 4.1' N ( 55.06756) LONGITUDE: 159° 25.3' W (-159.42189)
The bench mark is a disk set into a large, broad, granite boulder, located
beneath the rock ledge paralleling the shoreline and 3 m (10 ft) inshore of the
apparent high water line.
BENCH MARK STAMPING: 9163 C 2009
DESIGNATION: 945 9163 C
MONUMENTATION: Tidal Station disk VM#: 19288
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 55° 4.0' N ( 55.06728) LONGITUDE: 159° 25.3' W (-159.42156)
The bench mark is a disk set into the outer tip of a large, flat boulder,
located 30 m (98 ft) east of bench mark 945 9163 B, and 1.0 m (3.2 ft) inshore
of the apparent high water line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 9459163 PUBLICATION DATE: 10/30/2009
Name: HERENDEEN ISLAND, SHUMAGIN ISLANDS
AK
NOAA Chart: 16556 Latitude: 55° 3.9' N ( 55.06556)
USGS Quad: STEPOVAK BAY (1963) Longitude: 159° 25.1' W (-159.41867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9163 D 2009
DESIGNATION: 945 9163 D
MONUMENTATION: Tidal Station disk VM#: 19289
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 55° 4.0' N ( 55.06697) LONGITUDE: 159° 25.3' W (-159.42092)
The bench mark is a disk set into the flat top of a large fractured bedrock
outcorp, located 70 m (230 ft) from the HORCON monument and 50 m (164 ft) from
bench mark 945 9163 C.
BENCH MARK STAMPING: 9163 E 2009
DESIGNATION: 945 9163 E
MONUMENTATION: Tidal Station disk VM#: 19290
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 55° 4.0' N ( 55.06647) LONGITUDE: 159° 25.2' W (-159.42033)
The bench mark is a disk set into the flat top of a boulder below the grassy
ledge, located 70 m (230 ft) from bench mark 945 9163 D and less than 10 m (33
ft) from HORCON monument.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 9459163 PUBLICATION DATE: 10/30/2009
Name: HERENDEEN ISLAND, SHUMAGIN ISLANDS
AK
NOAA Chart: 16556 Latitude: 55° 3.9' N ( 55.06556)
USGS Quad: STEPOVAK BAY (1963) Longitude: 159° 25.1' W (-159.41867)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: HORCON
DESIGNATION: HERENDEEN 2009
MONUMENTATION: Horizontal Station disk VM#: 19291
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID#: BBBK57
LATITUDE: 55° 4.0' N ( 55.06647) LONGITUDE: 159° 25.2' W (-159.42025)
The bench mark is a disk set flush into a broad, fractured, exposed section of
bedrock at the base of a vegetation-covered slope and circled by a ring of
grass, located less than 10 m (33 ft) from bench mark 945 9163 E.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 9459163 PUBLICATION DATE: 10/30/2009
Name: HERENDEEN ISLAND, SHUMAGIN ISLANDS
AK
NOAA Chart: 16556 Latitude: 55° 3.9' N ( 55.06556)
USGS Quad: STEPOVAK BAY (1963) Longitude: 159° 25.1' W (-159.41867)
T I D A L D A T U M S
Tidal datums at HERENDEEN ISLAND, SHUMAGIN ISLANDS based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: July 2009 - July 2009
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9459450 SAND POINT, POPOF ISLAND
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.252
MEAN HIGH WATER MHW = 2.020
MEAN TIDE LEVEL MTL = 1.216
MEAN SEA LEVEL MSL = 1.199
MEAN LOW WATER MLW = 0.413
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
9163 A 2009 3.243 1.223
9163 B 2009 3.359 1.339
9163 C 2009 3.389 1.369
9163 D 2009 4.564 2.544
9163 E 2009 5.227 3.207
HORCON 4.978 2.958
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 9459163 PUBLICATION DATE: 10/30/2009
Name: HERENDEEN ISLAND, SHUMAGIN ISLANDS
AK
NOAA Chart: 16556 Latitude: 55° 3.9' N ( 55.06556)
USGS Quad: STEPOVAK BAY (1963) Longitude: 159° 25.1' W (-159.41867)
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.
Station Location
Published bench mark
Unpublished bench mark
