U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 10/04/2000
Station ID: 9448576 SUPERCEDED DATE: 04/21/2003
Name: SNEEOOSH POINT, SKAGIT BAY
WASHINGTON
NOAA Chart: 18427 Latitude: 48° 24.0' N
USGS Quad: CRESCENT HARBOR Longitude: 122° 32.9' W
To reach the tidal bench marks from Anacortes drive east on Highway 20, turn
right on Reservation Road, turn right on Sneeoosh Road, turn right on Warren
Avenue, then right on the Beach Road, then left into the parking lot for Hpoe
Island Inn. The tidal bench marks are located along the Beach Road and the
gauge was located on the west (beach) side of the Inn, under the wood deck.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: LONE TREE PT SITC 20.3 FT NAVD88
DESIGNATION: 944 8576 LONE TREE
MONUMENTATION: Bench Mark disk VM#: 16170
AGENCY: Swinomish Indian Tribal Community (SITC) PID:
SETTING CLASSIFICATION: Concrete pavement
The primary bench mark is a disk set in concrete pavement at Lone Tree Point
near Thousand Trails campsite on Sneeoosh Road, 13.30 m (43.6 ft) west of the
centerline of a gravel road, 6.10 m (20.0 ft) north of the center of a lone
conifer tree, and 5.50 m (18.0 ft) east of west edge of the Lone Tree Point.
BENCH MARK STAMPING: 8576 A 2000
DESIGNATION: 944 8576 A
MONUMENTATION: Tidal Station disk VM#: 16171
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Bedrock
The bench mark is a disk set in bedrock on the south side of the Hope Island
Inn, 12.60 m (41.3 ft) west of the SE corner of the Inn, 12.15 m (39.9 ft) east
of the west edge of the concrete foundation wall where it transitions to rock
wall of the Inn, 2.20 m (7.2 ft) south of the concrete foundation wall, and at
apparent high water line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 10/04/2000
Station ID: 9448576 SUPERCEDED DATE: 04/21/2003
Name: SNEEOOSH POINT, SKAGIT BAY
WASHINGTON
NOAA Chart: 18427 Latitude: 48° 24.0' N
USGS Quad: CRESCENT HARBOR Longitude: 122° 32.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8576 B 2000
DESIGNATION: 944 8576 B
MONUMENTATION: Tidal Station disk VM#: 16172
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Bedrock
The bench mark is a disk set in bedrock on the south side of the second rocky
point north of the Hope Island Inn, 21.50 m (70.5 ft) north of 4 m high x 2 m
wide x 7 m deep (13 ft high x 7 ft wide x 23 ft deep) cave in the bedrock beach
bluff, 3.40 m (11.2 ft) NE of west end of rocky point, 2 m (7 ft) SW of a 1.30 m
(4.3 ft) high vertical rock face on the point, and 1.30 m (4.3 ft) above cobble
beach at the apparent high water line.
BENCH MARK STAMPING: 8576 C 2000
DESIGNATION: 944 8576 C
MONUMENTATION: Tidal Station disk VM#: 16173
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Bedrock
The bench mark is a disk set in bedrock at the head of the first small cove
north of the Hope Island Inn, 11.90 m (39.0 ft) south of the south buttress of
the concrete retaining wall, 3.40 m (11.2 ft) north of bottom concrete step
leading to wood stairway up bluff, 0.50 m (1.6 ft) east of the edge of bedrock
and cobble/gravel beach, and at apparent high water line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 10/04/2000
Station ID: 9448576 SUPERCEDED DATE: 04/21/2003
Name: SNEEOOSH POINT, SKAGIT BAY
WASHINGTON
NOAA Chart: 18427 Latitude: 48° 24.0' N
USGS Quad: CRESCENT HARBOR Longitude: 122° 32.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8576 D 2000
DESIGNATION: 944 8576 D
MONUMENTATION: Tidal Station disk VM#: 16174
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Bedrock
The bench mark is a disk set in bedrock outcrop just south of first rocky point
south of Lone Tree Point, 35.60 m (116.8 ft) NW of NW corner of 2.50 m (8.2 ft)
high concrete retaining wall, 8.60 m (28.2 ft) SE of bottom concrete/rock step
up rocky point, 1.90 m (6.2 ft) NW of prominent rocky point just south of main
point, and about 1 m (3 ft) above sand/gravel beach.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 10/04/2000
Station ID: 9448576 SUPERCEDED DATE: 04/21/2003
Name: SNEEOOSH POINT, SKAGIT BAY
WASHINGTON
NOAA Chart: 18427 Latitude: 48° 24.0' N
USGS Quad: CRESCENT HARBOR Longitude: 122° 32.9' W
T I D A L D A T U M S
Tidal datums at SNEEOOSH POINT, SKAGIT BAY based on:
LENGTH OF SERIES: 172 hws and 171 lws
TIME PERIOD: June 1 - August 29, 2000
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 9449880 FRIDAY HARBOR, SAN JUAN CHANNEL
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.377
MEAN HIGH WATER MHW = 3.099
MEAN TIDE LEVEL MTL = 1.957
MEAN SEA LEVEL MSL = 1.945
MEAN LOW WATER MLW = 0.814
North American Vertical Datum NAVD88 = 0.650
MEAN LOWER LOW WATER MLLW = 0.000
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
LONE TREE PT SITC 20.3 FT NAVD88 6.837 3.738
8576 A 2000 3.304 0.205
8576 B 2000 3.092 -0.008
8576 C 2000 3.127 0.028
8576 D 2000 4.038 0.939
Foot Notes:
* The NAVD 88 elevation for Bench Mark Lone Tree Pt SITC 20.3 FT was determined
through a survey by Reid Middleton, Inc and provided to the National Ocean
Service (NOS) at the request of the Swinomish Indian Tribal Community (SITC)
for establishing the relationship between tidal datums and the geodetic datum
NAVD88 and other bench marks in the leveling network on Fidalgo Island.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 10/04/2000
Station ID: 9448576 SUPERCEDED DATE: 04/21/2003
Name: SNEEOOSH POINT, SKAGIT BAY
WASHINGTON
NOAA Chart: 18427 Latitude: 48° 24.0' N
USGS Quad: CRESCENT HARBOR Longitude: 122° 32.9' 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.