U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9450251 PUBLICATION DATE: 08/23/2016
Name: ENTRANCE TO WINDY COVE
AK
NOAA Chart: 17408 Latitude: 55° 2.1' N ( 55.03544)
USGS Quad: CRAIG (A-4) Longitude: 133° 1.4' W (-133.02378)
To reach the tidal bench marks from Hydaburg, AK, by boat, start at the R 4
buoy south of town. Proceed NW to the flashing red, 4 s 8 light on course 320
T for 0.45 NM, then turn North on course 352 T for 0.78 NM. From this point NE
of Comma Island, proceed West on course 277 T for 0.66 NM, then turn South on
course 180 T for 1.22 NM into South Pass. Turn SW on course 236 T for 0.81 NM to
the West of Panhandle Island, then back SE on course 140 T for 1.01 NM. Exiting
South pass, turn SW on course 219 T for 0.90 NM, then 260 T for 0.69 NM. Proceed
into Tlevak Straight on course 235 T for 2.54 NM before heading South on course
180 T for 5.98 NM. After passing the flashing, 4 s light SE of Reef Point, turn
West into Baldy Bay on course 270 T for 2.05 NM. Proceed SW towards Windy Cove
on course 221 T for 0.46 NM, then south on course 180 T for 380 yds. Turn East
into a small cove, prior to reaching the narrow passage into Windy cove, on
course 088 T for 200 yds. The tidal bench marks are set in bedrock, located on
the far West end of the small island marking the entrance to Windy Cove. The
tide gage was installed at 55 02.11 N, 133 01.43 W. underneath tree cover.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0251-A 2016
DESIGNATION: 945 0251-A
MONUMENTATION: Bench Mark disk VM#: 21987
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID#: BBFG38
LATITUDE: 55° 2.1' N ( 55.03511) LONGITUDE: 133° 1.4' W (-133.02394)
The primary benchmark is a standard brass disk stamped 0251-A 2016 set with
concrete on the pinnacle of a rocky outcrop, on the Southern side of the unnamed
island, approximately 15m South of a group of trees 18-24 in diameter, at the
entrance to Windy Cove, and 5m South of a large downed tree with significant
vegetation growth. This benchmark becomes completely submerged during high tide.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9450251 PUBLICATION DATE: 08/23/2016
Name: ENTRANCE TO WINDY COVE
AK
NOAA Chart: 17408 Latitude: 55° 2.1' N ( 55.03544)
USGS Quad: CRAIG (A-4) Longitude: 133° 1.4' W (-133.02378)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0251-B 2016
DESIGNATION: 945 0251-B
MONUMENTATION: Bench Mark disk VM#: 21988
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 55° 2.1' N ( 55.03539) LONGITUDE: 133° 1.4' W (-133.02414)
The benchmark is a standard brass disk stamped 0251-B 2016 set with concrete
in a rocky outcrop located 35m NW of the Primary benchmark on the W side of the
unnamed island, 10m NW of a patch of small vegetation. The benchmark is set
close to the water s edge and could cover during higher tides.
BENCH MARK STAMPING: 0251-C 2016
DESIGNATION: 945 0251-C
MONUMENTATION: Bench Mark disk VM#: 21989
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 55° 2.1' N ( 55.03539) LONGITUDE: 133° 1.4' W (-133.02397)
The benchmark is a standard brass disk stamped 0251-C 2016 set with concrete
in a rocky outcrop located 11.5 meters NE of benchmark 0251-B on the N side of
the unnamed island, lies directly W of a 1-2' high ledge which marks a small
channel that water flows through during high tide and is dry during low tide and
directly N of a group of trees 18-24 in diameter.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9450251 PUBLICATION DATE: 08/23/2016
Name: ENTRANCE TO WINDY COVE
AK
NOAA Chart: 17408 Latitude: 55° 2.1' N ( 55.03544)
USGS Quad: CRAIG (A-4) Longitude: 133° 1.4' W (-133.02378)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0251-D 2016
DESIGNATION: 945 0251-D
MONUMENTATION: Bench Mark disk VM#: 21990
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 55° 2.1' N ( 55.03539) LONGITUDE: 133° 1.4' W (-133.02389)
The benchmark is a standard brass disk stamped 0251-D 2016 set with concrete
in a rocky outcrop on the Eastern side of unnamed island located 18.2 meters SE
of benchmark 0251-C and 11 meters NW of benchmark 0251-E. This benchmark lies
on the E side of a small channel that water flows through during high tide and
is dry at low tide. This benchmark is completely submerged during high tide.
Trees are directly overhead.
BENCH MARK STAMPING: 0215-E 2016
DESIGNATION: 945 0251-E
MONUMENTATION: Bench Mark disk VM#: 21991
AGENCY: National Ocean SErvice IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 55° 2.1' N ( 55.03522) LONGITUDE: 133° 1.4' W (-133.02367)
The benchmark is standard brass disk stamped 0251-E 2016 set with concrete in
a rocky outcrop on the E side of the unnamed island and located 11 meters from
benchmark 0251-D, directly S of a patch of trees 4-12" in diameter. This
benchmark lies in between two small channels that allow water to flow through
during high tide and are dry at low tide. The channel to the East is about 4m
East of the benchmark and the channel to the West is about 8m from the
benchmark. A small cove is directly South.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9450251 PUBLICATION DATE: 08/23/2016
Name: ENTRANCE TO WINDY COVE
AK
NOAA Chart: 17408 Latitude: 55° 2.1' N ( 55.03544)
USGS Quad: CRAIG (A-4) Longitude: 133° 1.4' W (-133.02378)
T I D A L D A T U M S
Tidal datums at ENTRANCE TO WINDY COVE based on:
LENGTH OF SERIES: 30 DAYS
TIME PERIOD: May 17, 2016 - June 15, 2016
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 = 3.972
MEAN HIGH WATER MHW = 3.704
MEAN TIDE LEVEL MTL = 2.086
MEAN SEA LEVEL MSL = 2.086
MEAN LOW WATER MLW = 0.468
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
0251-A 2016 3.795 0.091
0251-B 2016 4.063 0.359
0251-C 2016 3.409 -0.294
0251-D 2016 3.728 0.025
0215-E 2016 3.548 -0.156
Foot Notes:
Data Quality Data from this station was collected using methodology that does
not meet CO-OPS highest level of accuracy (no more than 10 cm, 95% Confidence
Interval (CI) referenced to a tidal datum). Recognizing that lower quality data
can be used for certain applications CO-OPS is making this data available to its
users with restraint. The average six-minute water level observations derived
from this system have an accuracy ranging from 10.0 - 30.0 cm, 95% CI on datum.
Users are cautioned to consider the accuracy of these data before using them for
critical navigational or coastal engineering purposes.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9450251 PUBLICATION DATE: 08/23/2016
Name: ENTRANCE TO WINDY COVE
AK
NOAA Chart: 17408 Latitude: 55° 2.1' N ( 55.03544)
USGS Quad: CRAIG (A-4) Longitude: 133° 1.4' W (-133.02378)
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.