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National Ocean Service
Datums Page Page 1 of 6
Station ID: 9442705 PUBLICATION DATE: 11/15/2016
Name: TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN
WA
NOAA Chart: 18485 Latitude: 48° 10.3' N ( 48.17111)
USGS Quad: OZETTE Longitude: 124° 44.2' W (-124.73694)
To reach the tide station from the Olympic National Park Ozette Campground
parking lot, walk the Cape Alava boardwalk trail 5.0 km (3.1 mi) west to the end
of the trail at the ocean coast, turn right and proceed north along the beach
1.2 km (0.75 mi) to the sand and stone isthmus connecting the mainland to
Tskawahyah (Cannonball) Island from mid to low tide, proceed 0.2 km (0.15 mi)
west across the spit to the island and the tide station at the SW corner of the
island. The bench marks are in bedrock outcrops around the perimeter of the
island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2705 A 2016
DESIGNATION: 944 2705 A
MONUMENTATION: Bench Mark disk VM#: 21946
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID#: BBFF77
LATITUDE: 48° 10.3' N ( 48.17097) LONGITUDE: 124° 44.2' W (-124.73617)
The primary bench mark is a disk set in a bedrock outcrop surrounded by
boulders, 69.58 m (228.3 ft) south of the NW end of the spine of rocks at the NW
corner of island, 54.77 m (179.7 ft) NW of center of rock cliff face below
grassy plateau extending S from the S side of the island and 8.2 m (26.9 ft)
above the beach, 29.49 m (96.8 ft) S of the rock cliff face at the head of the
beach directly below a pinnacle rock extending out of the grassy slope leading
to the highest point of the island on the W side of the island, 16.34 m (53.6
ft) WSW of a small ravine created by a rockslide S of the cliff face at the SW
corner of the island, 2.18 m (7.2 ft) E of W edge of the bedrock outcrop and
about 2.16 m (7.1 ft) higher than the stone beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 9442705 PUBLICATION DATE: 11/15/2016
Name: TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN
WA
NOAA Chart: 18485 Latitude: 48° 10.3' N ( 48.17111)
USGS Quad: OZETTE Longitude: 124° 44.2' W (-124.73694)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2705 B 2016
DESIGNATION: 944 2705 B
MONUMENTATION: Bench Mark disk VM#: 21947
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 48° 10.3' N ( 48.17142) LONGITUDE: 124° 44.2' W (-124.73611)
The bench mark is a disk set in a bedrock spine extending to the NW, 18.49 m
(60.7 ft) SE of NW end of the rock spine, 1.04 m (3.4 ft) W of the east edge of
the outcrop ledge, 0.98 m (3.2 ft) N of the rock cliff face extending 6 m (20
ft) above stone beach, and about 3.08 m (10.1 ft) higher than the stone beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 9442705 PUBLICATION DATE: 11/15/2016
Name: TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN
WA
NOAA Chart: 18485 Latitude: 48° 10.3' N ( 48.17111)
USGS Quad: OZETTE Longitude: 124° 44.2' W (-124.73694)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: INDIAN 1930 RM 2 1975
DESIGNATION: INDIAN 1930 RM 2 1975
MONUMENTATION: Reference Mark disk VM#: 21948
AGENCY: National Ocean Service IDB PID#: TS0328
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 48° 10.3' N ( 48.17150) LONGITUDE: 124° 44.1' W (-124.73461)
The bench mark is set in the high point of a bedrock beach, 32.34 m (106.1 ft) N
of the E most bedrock outcrop on the N side of the island, 24.36 m (79.9 ft) W
of the E edge of the bedrock beach where it joins a sand beach, 15.86 m (52.0
ft) N of the NW corner of the island, and 0.52 m (1.7 ft) WSW of the highest
point of the bedrock outcrop that the bench mark is set in.
BENCH MARK STAMPING: 2705 D 2016
DESIGNATION: 944 2705 D
MONUMENTATION: Bench Mark disk VM#: 21949
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 48° 10.2' N ( 48.17069) LONGITUDE: 124° 44.1' W (-124.73547)
The bench mark is set in a bedrock outcrop, 50.20 m (164.7 ft) W of a bedrock
cliff face at the SE corner of the island, 11.15 m (36.6 ft) E of the center of
a cliff face below a grassy plateau extending S from the S side of the island
and 8.2 m (26.9 ft) above the beach, 5.23 m (17.2 ft) SW of the bottom of a draw
cut into the S side of the island, and 1.24 m (4.1 ft) SE of the rock face along
the S side of the island.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 9442705 PUBLICATION DATE: 11/15/2016
Name: TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN
WA
NOAA Chart: 18485 Latitude: 48° 10.3' N ( 48.17111)
USGS Quad: OZETTE Longitude: 124° 44.2' W (-124.73694)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2705 C 2016
DESIGNATION: 944 2705 C
MONUMENTATION: Bench Mark disk VM#: 21950
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 48° 10.3' N ( 48.17139) LONGITUDE: 124° 44.1' W (-124.73547)
The bench mark is a disk set in a bedrock point extending N from the middle of
the N side of the island, 62.34 m (204.5 ft) E of the seaward point of the spine
of rock extending NW from the NW corner of the island, 4.26 m (14.0 ft) S of the
tip of the bedrock point, and 1.81 m (5.9 ft) N of a round bulge in the cliff
face.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 9442705 PUBLICATION DATE: 11/15/2016
Name: TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN
WA
NOAA Chart: 18485 Latitude: 48° 10.3' N ( 48.17111)
USGS Quad: OZETTE Longitude: 124° 44.2' W (-124.73694)
T I D A L D A T U M S
Tidal datums at TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: June 2016 - August 2016
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9443090 NEAH BAY, STRAIT OF JUAN DE FUCA
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.655
MEAN HIGH WATER MHW = 2.429
MEAN TIDE LEVEL MTL = 1.436
MEAN SEA LEVEL MSL = 1.422
MEAN LOW WATER MLW = 0.444
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2705 A 2016 3.230 0.801
2705 B 2016 4.564 2.135
INDIAN 1930 RM 2 1975 2.702 0.273
2705 D 2016 3.751 1.322
2705 C 2016 4.464 2.035
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 9442705 PUBLICATION DATE: 11/15/2016
Name: TSKAWAHYAH ISLAND, CAPE ALAVA, PACIFIC OCEAN
WA
NOAA Chart: 18485 Latitude: 48° 10.3' N ( 48.17111)
USGS Quad: OZETTE Longitude: 124° 44.2' W (-124.73694)
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.