U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9451012 PUBLICATION DATE: 02/27/2006
Name: BRADFIELD CANAL
AK
NOAA Chart: 17385 Latitude: 56° 11.0' N ( 56.18330)
USGS Quad: Bradfield Canal A-5 Longitude: 131° 34.3' W (-131.57200)
To reach the bench marks by ship which are located on the south shore of
Bradfield Canal east of Blake Island approximately 21.3 km (11.5 nm), from the
City of Wrangell, AK, transit southbound through Eastern Passage approximately
21.9 km (11.8 nm) until approaching The Narrows, transit through the narrows
eastbound approximately 2.8 km (1.5 nm), continue southbound through Blake
Channel approximately 21.3 km (11.5 nm). After passing Blake Island enter
Bradfield Canal and transit east through the canal approximately 17.6 km (9.5
nm) until approaching Duck Pt. The bench marks are located 3.5 km (1.9 nm) east
of Duck Pt, on the southern shore of Bradfield Canal at position 56 11.747' N,
131 33.468'W. Total transit distance from the City of Wrangell is approximately
76.9 km (41.5 nm). There are a few prominent features in the bench mark area.
Upon approaching, there is a large white cliff face to the southeast of the
bench marks, as well as a rocky outcropping, and ledge in the general location
of the bench marks.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1012 B 2005
DESIGNATION: 945 1012 B
MONUMENTATION: Tidal Station disk VM#: 17989
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 11.7' N ( 56.19500) LONGITUDE: 131° 33.5' W (-131.55800)
The primary bench mark is a disk set flush in bedrock, 32.0 m (105 ft) SW of
bench mark 945 1012 C 2005, 9.7 m (31.8 ft) west of the surrounding tree line,
and 3.4 m (11.2 ft) NNW of the rocky outcropping.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9451012 PUBLICATION DATE: 02/27/2006
Name: BRADFIELD CANAL
AK
NOAA Chart: 17385 Latitude: 56° 11.0' N ( 56.18330)
USGS Quad: Bradfield Canal A-5 Longitude: 131° 34.3' W (-131.57200)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1012 A 2005
DESIGNATION: 945 1012 A
MONUMENTATION: Tidal Station disk VM#: 17990
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 11.8' N ( 56.19670) LONGITUDE: 131° 33.4' W (-131.55700)
The bench mark is a disk set flush in bedrock approximately 100 m (328 ft) NW of
a large white cliff face, 25 m (82 ft) NE of the rocky outcropping, 24.80 m
(81.4 ft) east of bench mark 945 1012 B 2005, and 6.0 m (19.7 ft) south of the
surrounding tree line.
BENCH MARK STAMPING: 1012 C 2005
DESIGNATION: 945 1012 C
MONUMENTATION: Tidal Station disk VM#: 17991
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 11.8' N ( 56.19670) LONGITUDE: 131° 33.5' W (-131.55800)
The bench mark is a disk set flush in bedrock, 30.0 m (98.4 ft) south of bench
mark 945 1012 D 2005, 21.6 m (70.9 ft) SE of the large SE boulder, and 4.8 m
(15.7 ft) NW of the surrounding tree line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9451012 PUBLICATION DATE: 02/27/2006
Name: BRADFIELD CANAL
AK
NOAA Chart: 17385 Latitude: 56° 11.0' N ( 56.18330)
USGS Quad: Bradfield Canal A-5 Longitude: 131° 34.3' W (-131.57200)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1012 D 2005
DESIGNATION: 945 1012 D
MONUMENTATION: Tidal Station disk VM#: 17992
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 11.8' N ( 56.19620) LONGITUDE: 131° 33.5' W (-131.55800)
The bench mark is a disk set flush in bedrock, 32.3 m (106 ft) SE of bench mark
945 1012 E 2005, 8.2 m (26.9 ft) SW of the surrounding tree line, and 3.8 m
(12.5 ft) NE of the large NW boulder.
BENCH MARK STAMPING: 1012 E 2005
DESIGNATION: 945 1012 D
MONUMENTATION: Tidal Station disk VM#: 17993
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 56° 11.8' N ( 56.19670) LONGITUDE: 131° 33.5' W (-131.55800)
The bench mark is a disk set flush in bedrock, 19 m (62.3 ft) NE of the bedrock
outcropping, and 6 m (19.7 ft) SE of the surrounding tree line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9451012 PUBLICATION DATE: 02/27/2006
Name: BRADFIELD CANAL
AK
NOAA Chart: 17385 Latitude: 56° 11.0' N ( 56.18330)
USGS Quad: Bradfield Canal A-5 Longitude: 131° 34.3' W (-131.57200)
T I D A L D A T U M S
Tidal datums at BRADFIELD CANAL based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: October 8, 2005 - November 7, 2005
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 = 5.055
MEAN HIGH WATER MHW = 4.770
MEAN TIDE LEVEL MTL = 2.622
MEAN SEA LEVEL MSL = 2.608
MEAN LOW WATER MLW = 0.474
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1012 B 2005 5.310 0.540
1012 A 2005 5.493 0.723
1012 C 2005 6.159 1.390
1012 D 2005 5.387 0.618
1012 E 2005 5.693 0.924
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9451012 PUBLICATION DATE: 02/27/2006
Name: BRADFIELD CANAL
AK
NOAA Chart: 17385 Latitude: 56° 11.0' N ( 56.18330)
USGS Quad: Bradfield Canal A-5 Longitude: 131° 34.3' W (-131.57200)
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.