U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 10/11/1988
Station ID: 9445388 SUPERCEDED DATE: 04/21/2003
Name: AYOCK, HOOD CANAL
WASHINGTON
NOAA Chart: 18445 Latitude: 47° 30.5' N
USGS Quad: THE BROTHERS Longitude: 123° 3.2' W
To reach the tidal bench marks from the post office at Lillipwaup, proceed 4.5
miles (7.2 km) NE along U.S. Highway 101, turn right onto a paved road leading
east to Ayock Beach, continue 0.1 mile (0.2 km) to the Ayock Beach pier, which
is 0.25 mile (0.4 km) NW of the tip of Ayock Point. The bench marks are in the
vicinity of th end of the pier and extend north along shoreline. The tide gage
and staff were mounted on the third piling from the seaward end of the SE side
of the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5388 D 1978
MONUMENTATION: Survey Disk VM#: 9053
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Bulkhead
The bench mark is set in the base of the southern end of a concrete bulkhead in
a 5-inch footing lip next to concrete steps leading to the water, 0.4 mile (0.6
km) NW of the tip of Ayock Point, 0.13 mile (0.21 km) north of the community
hall, and 0.13 mile (0.21 km) NW of the pier.
BENCH MARK STAMPING: 5388 E 1978
MONUMENTATION: Survey Disk VM#: 9054
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Bulkhead
The bench mark is set in top of the NE corner of a concrete bulkhead, 0.4 mile
(0.6 km) NW of the tip of Ayock Point, 0.13 mile (0.21 km) north of the
community hall, and 0.13 mile (0.21 km) NW of the pier, and just south of old
steps leading to the water.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 10/11/1988
Station ID: 9445388 SUPERCEDED DATE: 04/21/2003
Name: AYOCK, HOOD CANAL
WASHINGTON
NOAA Chart: 18445 Latitude: 47° 30.5' N
USGS Quad: THE BROTHERS Longitude: 123° 3.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: F 464 1973
MONUMENTATION: Survey Disk VM#: 9055
AGENCY: PID#: SY1238
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument 3.6 miles (5.8 km) NE along U.S.
Highway 101 from the post office at Lilliwaup, 0.3 mile (0.5 km) NE of milepost
324 at junction of a private driveway leading NE downhill, 74.5 feet (22.7 m) SE
and across highway from guy pole 179SN215GS, 61.5 feet (18.7 m) NW of centerline
of driveway, 1.1 feet (0.3 m) SW of power pole 179-N215 with a guy pole, and 1.0
feet (0.3 m) NE of a witness post, projects 0.2 foot (0.1 m) above ground level,
and set 1 foot (0.3 m) below highway level.
BENCH MARK STAMPING: G 464 1973
MONUMENTATION: Survey Disk VM#: 9056
AGENCY: PID#: SY1236
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument 4.5 miles (7.2 km) NE along U.S.
Highway 101 from the post office a Lilliwaup, at the junction of asphalt road
leading east to Ayock Beach, 38.5 feet (11.7 m) east of the centerline of the
highway, 34 feet (10.4 m) north of the centerline of the road leading to Ayock
Beach, 2.0 feet (0.6 m) north of utility pole #N231 194 with transformer and
flood light, 2.0 feet (0.6 m) south of a witness post, projects 0.3 foot (0.1 m)
above ground level, and 1.5 foot (0.5 m) above the highway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 10/11/1988
Station ID: 9445388 SUPERCEDED DATE: 04/21/2003
Name: AYOCK, HOOD CANAL
WASHINGTON
NOAA Chart: 18445 Latitude: 47° 30.5' N
USGS Quad: THE BROTHERS Longitude: 123° 3.2' W
T I D A L D A T U M S
Tidal datums at AYOCK, HOOD CANAL based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: FEBRUARY 1978
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 9447130 SEATTLE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (02/09/1978) = 14.51
MEAN HIGHER HIGH WATER MHHW = 11.37
MEAN HIGH WATER MHW = 10.42
MEAN TIDE LEVEL MTL = 6.73
MEAN LOW WATER MLW = 3.04
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (02/04/1978) = -1.00
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
5388 D 1978 12.69 2.27
5388 E 1978 18.57 8.15
F 464 1973 132.47 122.05
G 464 1973 59.35 48.93
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 10/11/1988
Station ID: 9445388 SUPERCEDED DATE: 04/21/2003
Name: AYOCK, HOOD CANAL
WASHINGTON
NOAA Chart: 18445 Latitude: 47° 30.5' N
USGS Quad: THE BROTHERS Longitude: 123° 3.2' W
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 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.