U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9445016 PUBLICATION DATE: 03/03/2015
Name: FOULWEATHER BLUFF, TWIN SPITS
WA
NOAA Chart: 18461 Latitude: 47° 55.6' N ( 47.92670)
USGS Quad: HANSVILLE Longitude: 122° 37.0' W (-122.61700)
To reach the tidal bench marks from the Hansville Community Church, proceed west
on Twin Spits Road for 3.4 miles (5.5 km) to a cul de sac at end of road, then
west 30.00m (98.42ft) and turn left (south). Walk 0.1 miles (0.15km) to the
dock. The bench marks are located around the private residences and the tide
gage and staff were located on the private residence dock.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5016 A 1977
DESIGNATION: 944 5016 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 9029
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID#: BBCT90
LATITUDE: 47° 55.6' N ( 47.92636) LONGITUDE: 122° 37.0' W (-122.61628)
The primary benchmark is a disk set in a concrete slab on top of the foundation
of a marine railway, 13.00 m (42.6ft) NNE from a concrete fire pit, 11.70 m
(38.4 ft) WSW from SE corner of a brown steel utility building, 8.50 m (27.8 ft)
shoreward of wooden retaining wall, 0.015 m (0.5ft) above the concrete
foundation of the marine railway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9445016 PUBLICATION DATE: 03/03/2015
Name: FOULWEATHER BLUFF, TWIN SPITS
WA
NOAA Chart: 18461 Latitude: 47° 55.6' N ( 47.92670)
USGS Quad: HANSVILLE Longitude: 122° 37.0' W (-122.61700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5016 B 1977
DESIGNATION: 944 5016 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 9030
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 47° 55.6' N ( 47.92628) LONGITUDE: 122° 37.0' W (-122.61628)
The benchmark is a disk set flush in NW corner of overgrown concrete foundation,
benchmark sits on an exposed corner closest to driveway, 56.9m (186.6ft) from
the center of Twin Spits Road, 29.6m (97 ft) from benchmark 5016 A 1977, 10.2m
(33.5 ft) north of the flag pole on property, 6.1m (20.0 ft) WSW to the SW
corner of the two-story house, 3.9m (12.8ft) from green access hole to septic
tank, 1.0m (3.28 ft) above surrounding grade.
BENCH MARK STAMPING: 5016 F 2012
DESIGNATION: 944 5016 F
MONUMENTATION: Tidal Station disk VM#: 20525
AGENCY: NOS IDB PID#:
SETTING CLASSIFICATION: Concrete slab OPUS PID:
LATITUDE: 47° 55.6' N ( 47.92692) LONGITUDE: 122° 36.9' W (-122.61525)
The benchmark is a disk set flush in concrete slab that is 0.6m x 0.6m (2ft x 2
ft) sitting adjacent to the West side of the liquid propane cylinder, 33m
(108.2ft) West of nearest fire hydrant, 27.7m (90.9ft) WSW from the centerline
of Twin Spits Road, 9.8m (32.1ft) NW from centerline of the private drive
running North-South off of Twin Spits Road, 6.3m (20.7ft) SSE from nearest
utility pole, 5.8m (19.0ft) east of the SE corner of nearest cabin.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9445016 PUBLICATION DATE: 03/03/2015
Name: FOULWEATHER BLUFF, TWIN SPITS
WA
NOAA Chart: 18461 Latitude: 47° 55.6' N ( 47.92670)
USGS Quad: HANSVILLE Longitude: 122° 37.0' W (-122.61700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5016 G 2012
DESIGNATION: 944 5016 G
MONUMENTATION: Tidal Station disk VM#: 20526
AGENCY: NOS IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 47° 55.6' N ( 47.92692) LONGITUDE: 122° 36.9' W (-122.61569)
The benchmark is a disk set flush in concrete, 119m (390.3ft) E from the end of
the pier, 63.8m (209.3ft) NE from the base of the pier, 16.2m (53.1ft) WSW from
the Southwest corner of the main house on the property, 3.5m (11.5ft) north of
Northwest corner of utility shed, 3m (9.8ft) inshore of mean high water, 2.0m
(6.56ft) north of boat ramp, set flush 0.6m (1.97ft) above the surrounding grade
on a poured concrete retaining wall.
BENCH MARK STAMPING: 5016 H 2012
DESIGNATION: 944 5016 H
MONUMENTATION: Tidal Station disk VM#: 20527
AGENCY: NOS IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 47° 55.6' N ( 47.92711) LONGITUDE: 122° 36.9' W (-122.61497)
The benchmark is a disk located on a poured concrete retaining wall adjacent to
the garage, approximately half-way from the overhead door to the southernmost
end of the retaining wall, 12.0m (39.4ft) east of the front door of 2604 NE Twin
Spits Road, 4.6m (15.1ft) WSW from the Southeast corner of the garage,; the
benchmark is set flush in the top of the retaining wall, 1.5m (4.9ft) above the
surrounding grade of the driveway.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9445016 PUBLICATION DATE: 03/03/2015
Name: FOULWEATHER BLUFF, TWIN SPITS
WA
NOAA Chart: 18461 Latitude: 47° 55.6' N ( 47.92670)
USGS Quad: HANSVILLE Longitude: 122° 37.0' W (-122.61700)
T I D A L D A T U M S
Tidal datums at FOULWEATHER BLUFF, TWIN SPITS based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: May 2012 - May 2012
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9447130 SEATTLE, PUGET SOUND
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.049
MEAN HIGH WATER MHW = 2.797
MEAN TIDE LEVEL MTL = 1.812
MEAN SEA LEVEL MSL = 1.791
MEAN LOW WATER MLW = 0.827
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
5016 A 1977 4.352 1.555
5016 B 1977 7.489 4.692
5016 F 2012 11.195 8.398
5016 G 2012 4.421 1.624
5016 H 2012 5.930 3.133
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9445016 PUBLICATION DATE: 03/03/2015
Name: FOULWEATHER BLUFF, TWIN SPITS
WA
NOAA Chart: 18461 Latitude: 47° 55.6' N ( 47.92670)
USGS Quad: HANSVILLE Longitude: 122° 37.0' W (-122.61700)
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.