U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9450906 PUBLICATION DATE: 12/01/2010
Name: BECK ISLAND, CLARENCE STRAIT
AK
NOAA Chart: 17382 Latitude: 56° 2.8' N ( 56.04670)
USGS Quad: PETERSBURG (A-2) Longitude: 132° 51.7' W (-132.86200)
To reach the bench marks from the village of Coffman Cove via boat, proceed 0.9
km (0.5 nm) NNW from the small boat harbor in Coffman Cove, then 1.9 km (1 nm)
NNE from Coffman Cove into Kashevarof Passage, then 2.8 km (1.5 nm) NW to the
southern end of Beck Island. The bench marks are located on bare rock on the
south side of the island. During the first installation the tide house was
located above the bare rock in the vegetation on the SE side of the island.
During the second installation the tide house was located above the bare rock in
the vegetation on the SW side of the island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0906 A 1978
DESIGNATION: 945 0906 A
MONUMENTATION: Tidal Station disk VM#: 16880
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 2.8' N ( 56.04670) LONGITUDE: 132° 51.7' W (-132.86200)
The primary bench mark is a disk set in a bedrock on the SW side of Beck Island,
40.10 m (131.6 ft) NW (273.2814 T) of bench mark 0906 C 1978, 22.77 m (74.7 ft)
SW (262.7356 T) of bench mark 0906 B 1978, 6.58 m (21.6 ft) WSW of a 3 m (10 ft)
high rock face and the vegetation line, and set flush with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9450906 PUBLICATION DATE: 12/01/2010
Name: BECK ISLAND, CLARENCE STRAIT
AK
NOAA Chart: 17382 Latitude: 56° 2.8' N ( 56.04670)
USGS Quad: PETERSBURG (A-2) Longitude: 132° 51.7' W (-132.86200)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0906 B 1978
DESIGNATION: 945 0906 B
MONUMENTATION: Tidal Station disk VM#: 16881
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock ledge OPUS PID:
LATITUDE: 56° 2.8' N ( 56.04670) LONGITUDE: 132° 51.7' W (-132.86200)
The bench mark is a disk set in a bedrock ledge and secured with concrete at the
top of a rock draw which bears southeasterly on the south side of Beck Island,
22.77 m (74.7 ft) SE (82.7356 T) of bench mark 0906 A 1978, 19.83 m (65.1 ft) NW
(271.8622 T) of bench mark 0906 D 1978, 18.20 m (59.7 ft) NW (286.5197 T) of
bench mark 0906 C 1978, 7.62 m (25.1 ft) ENE of a high rock point at the edge of
vegetation, 0.84 m (2.8 ft) north of the edge of the rock ledge, and set flush
with the ground.
BENCH MARK STAMPING: 0906 C 1978
DESIGNATION: 945 0906 C
MONUMENTATION: Tidal Station disk VM#: 16882
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 2.8' N ( 56.04670) LONGITUDE: 132° 51.7' W (-132.86200)
The bench mark is a disk set in a bedrock and secured with concrete on the SE
side of Beck Island, 27.87 m (91.4 ft) SW (226.1533 T) of bench mark 0906 E
1978, 18.20 m (59.7 ft) SE (106.5197 T) of bench mark 0906 B 1978, 5.11 m (16.8
ft) SW (207.6033 T) of bench mark 0906 D 1978, 10.13 m (33.2 ft) SE of a 4 m (13
ft) high rock face and the vegetation line that is at the top of a rock draw
which bears northerly, and set flush with the ground and canted approximately 5
to the south.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9450906 PUBLICATION DATE: 12/01/2010
Name: BECK ISLAND, CLARENCE STRAIT
AK
NOAA Chart: 17382 Latitude: 56° 2.8' N ( 56.04670)
USGS Quad: PETERSBURG (A-2) Longitude: 132° 51.7' W (-132.86200)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0906 D 1978
DESIGNATION: 945 0906 D
MONUMENTATION: Tidal Station disk VM#: 16883
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 2.8' N ( 56.04670) LONGITUDE: 132° 51.7' W (-132.86200)
The bench mark is a disk set in a bedrock and secured with concrete on the SE
side of Beck Island, 23.10 m (75.8 ft) SW (230.7228 T) of bench mark 0906 E
1978, 19.83 m (65.1 ft) SE (91.8622 T) of bench mark 0906 B 1978, 5.11 m (16.8
ft) NNE (27.6033 T) of bench mark 0906 C 1978, 8.35 m (27.4 ft) ESE of a 4 m (13
ft) high rock bluff and the vegetation line that is at the top of a rock draw
which bears northerly, and set flush with the ground and canted approximately 5
to the SE.
BENCH MARK STAMPING: 0906 E 1978
DESIGNATION: 945 0906 E
MONUMENTATION: Tidal Station disk VM#: 16884
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 2.8' N ( 56.04670) LONGITUDE: 132° 51.7' W (-132.86200)
The bench mark is a disk set in a bedrock and secured with concrete on the SE
side of Beck Island, 87 m (285 ft) SSW of a pominent pointed boulder on the NE
side of Beck Island, 27.87 m (91.4 ft) NE (46.1533 T) of bench mark 0906 C 1978,
23.10 m (75.8 ft) NE (50.7228 T) of bench mark 0906 D 1978, 8.26 m (27.1 ft) SE
of a high rock outcrop and the vegetation line, and set flush with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9450906 PUBLICATION DATE: 12/01/2010
Name: BECK ISLAND, CLARENCE STRAIT
AK
NOAA Chart: 17382 Latitude: 56° 2.8' N ( 56.04670)
USGS Quad: PETERSBURG (A-2) Longitude: 132° 51.7' W (-132.86200)
T I D A L D A T U M S
Tidal datums at BECK ISLAND, CLARENCE STRAIT based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: August 2002 - August 2002
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9450460 KETCHIKAN, TONGASS NARROWS
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 4.920
MEAN HIGH WATER MHW = 4.643
MEAN TIDE LEVEL MTL = 2.564
MEAN SEA LEVEL MSL = 2.553
MEAN LOW WATER MLW = 0.485
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
0906 A 1978 6.611 1.968
0906 B 1978 8.095 3.452
0906 C 1978 7.993 3.350
0906 D 1978 8.332 3.689
0906 E 1978 7.567 2.924
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9450906 PUBLICATION DATE: 12/01/2010
Name: BECK ISLAND, CLARENCE STRAIT
AK
NOAA Chart: 17382 Latitude: 56° 2.8' N ( 56.04670)
USGS Quad: PETERSBURG (A-2) Longitude: 132° 51.7' W (-132.86200)
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.