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National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9465182 PUBLICATION DATE: 03/19/2019
Name: BLACK ROCK, WALRUS IS BRISTOL B
AK
NOAA Chart: Latitude: 58° 42.5' N ( 58.70830)
USGS Quad: Longitude: 160° 11.3' W (-160.18800)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1948
DESIGNATION: 946 5182 TIDAL 1
MONUMENTATION: Survey disk VM#: 15328
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 58° 42.5' N ( 58.70830) LONGITUDE: 160° 11.3' W (-160.18800)
The bench mark is a disk set in a segment of rugged rock ledge, one of several
such segments lying about 137.16 m (450.0 ft) east of Black Rock Proper, in
Bristol Bay, 3.35 m (11.0 ft) above approximate mean lower low water and 8 m (26
ft) SE of bench mark 5182 B 1985 and 15.54 m (51.0 ft) north of bench mark 5182
A 1985.
BENCH MARK STAMPING: NO 2 1948
DESIGNATION: 946 5182 TIDAL 2
MONUMENTATION: Survey disk VM#: 15329
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID:
SETTING CLASSIFICATION: Rocky upthrust OPUS PID:
LATITUDE: 58° 42.5' N ( 58.70830) LONGITUDE: 160° 11.3' W (-160.18800)
The bench mark is a disk located on a rocky upthrust 4 m (13 ft) above
approximate mean lower low water, located in the same general area as bench mark
NO 1 1948, 7 m (23 ft) west of bench mark 5182 A 1985, and 10.36 m (34.0 ft) SE
of bench mark NO 3 1948. Rocky upthrust is on a rugged rock segment SSW of
bench mark NO 1 1948, one of several such segments lying about 137.16 m (450.0
ft) east of Black Rock Proper.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9465182 PUBLICATION DATE: 03/19/2019
Name: BLACK ROCK, WALRUS IS BRISTOL B
AK
NOAA Chart: Latitude: 58° 42.5' N ( 58.70830)
USGS Quad: Longitude: 160° 11.3' W (-160.18800)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1948
DESIGNATION: 946 5182 TIDAL 3
MONUMENTATION: Survey disk VM#: 15330
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID:
SETTING CLASSIFICATION: Rock segment OPUS PID:
LATITUDE: 58° 42.5' N ( 58.70830) LONGITUDE: 160° 11.3' W (-160.18800)
The bench mark is a disk located on the rugged rock segment nearest to Black
Rock Proper, located in the same general area as bench mark NO 1 1948, 10.36 m
(34.0 ft) NW of bench mark NO 2 1948, and 4.57 m (15.0 ft) above the approximate
mean lower low water. Rugged rock segment is WSW of bench mark NO 1 1948.
BENCH MARK STAMPING: 5182 A 1985
DESIGNATION: 946 5182 A 1985
MONUMENTATION: Survey disk VM#: 15331
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Set in bedrock in rocky upthrust OPUS PID:
LATITUDE: 58° 42.5' N ( 58.70830) LONGITUDE: 160° 11.3' W (-160.18800)
The bench mark is a disk set in bedrock in a rocky upthrust 4 m (13 ft) above
the approximate mean lower low water, 15.54 m (51.0 ft) south of bench mark NO 1
1948 and 7 m (23 ft) east of bench mark NO 2 1948, located on a rugged rock
segment, one of several such segments lying about 137.16 m (450.0 ft) east of
Black Rock proper.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9465182 PUBLICATION DATE: 03/19/2019
Name: BLACK ROCK, WALRUS IS BRISTOL B
AK
NOAA Chart: Latitude: 58° 42.5' N ( 58.70830)
USGS Quad: Longitude: 160° 11.3' W (-160.18800)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5182 B 1985
DESIGNATION: 946 5182 B 1985
MONUMENTATION: Survey disk VM#: 15332
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Rocky barnacle OPUS PID:
LATITUDE: 58° 42.5' N ( 58.70830) LONGITUDE: 160° 11.3' W (-160.18800)
The bench mark is a disk set in a rocky barnacle covered ledge projecting north
from rock segment that bench mark NO 1 1948 is located on, 7.92 m (26.0 ft) NW
of bench mark NO 1 1948 and about 2.74 m (9.0 ft) approximate mean lower low
water.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9465182 PUBLICATION DATE: 03/19/2019
Name: BLACK ROCK, WALRUS IS BRISTOL B
AK
NOAA Chart: Latitude: 58° 42.5' N ( 58.70830)
USGS Quad: Longitude: 160° 11.3' W (-160.18800)
T I D A L D A T U M S
Tidal datums at BLACK ROCK, WALRUS IS BRISTOL B based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: July 1986 - August 1986
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9463502 PORT MOLLER, BRISTOL BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.066
MEAN HIGH WATER MHW = 2.740
MEAN SEA LEVEL MSL = 1.630
MEAN TIDE LEVEL MTL = 1.623
MEAN LOW WATER MLW = 0.505
MEAN LOWER LOW WATER MLLW = 0.000
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 1 1948 2.770 0.030
NO 2 1948 3.254 0.514
NO 3 1948 3.673 0.933
5182 A 1985 3.496 0.756
5182 B 1985 2.302 -0.438
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9465182 PUBLICATION DATE: 03/19/2019
Name: BLACK ROCK, WALRUS IS BRISTOL B
AK
NOAA Chart: Latitude: 58° 42.5' N ( 58.70830)
USGS Quad: Longitude: 160° 11.3' W (-160.18800)
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.