U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9440575 PUBLICATION DATE: 08/09/2004
Name: KNAPPTON
WA
NOAA Chart: 18521 Latitude: 46° 16.1' N ( 46.26830)
USGS Quad: KNAPPTON Longitude: 123° 49.6' W (-123.82700)
To reach the tidal bench marks from Astoria, Oregon, proceed north on U.S.
Highway 101 across the Columbia River toll bridge, then turn right and proceed
east on U.S. Highway 401 for 5.23 km (3.25 mi) to the old Columbia River
Quarantine Station and two buildings resembling barracks north of U.S. Highway
401. The bench marks are in the vicinity of the old building and Mr. Clarence
Bell's property. The tide gage and staff were opposite the Quarantine Station,
mounted offshore on the two dolphins furthest east and beyond the piling ruins.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0575 A 1981
DESIGNATION: 944 0575 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 8945
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Gate footing OPUS PID:
LATITUDE: 46° 16.1' N ( 46.26830) LONGITUDE: 123° 49.6' W (-123.82700)
The primary bench mark is a disk set flush in a concrete and rock gate footing
located on the south side of U.S. Highway 401 across from the property belonging
to Mr. Clarence Bell, 53 m (175 ft) NE of the end of a highway guardrail, 15 m
(50 ft) SW of the centerline of U.S. Highway 401, and 0.24 m (0.8 ft) SW of the
south gate post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9440575 PUBLICATION DATE: 08/09/2004
Name: KNAPPTON
WA
NOAA Chart: 18521 Latitude: 46° 16.1' N ( 46.26830)
USGS Quad: KNAPPTON Longitude: 123° 49.6' W (-123.82700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0575 B 1981
DESIGNATION: 944 0575 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 8946
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete footing for flagpole OPUS PID:
LATITUDE: 46° 16.1' N ( 46.26830) LONGITUDE: 123° 49.6' W (-123.82700)
The bench mark is a disk set flush in a 1.6 m x 1.2 m (5.2 ft x 3.8 ft) concrete
footing for a flagpole on the property belonging to Mr. Clarence Bell, 64 m (210
ft) SE of bench mark 0575 C 1981, 46 m (152 ft) south of bench mark 0575 D 1981,
25.97 m (85.2 ft) NW of the centerline of U.S. Highway 401, 6.86 m (22.5 ft) SW
of the centerline of the road to Bell's property, and 0.37 m (1.2 ft) north of
the base of the flagpole.
BENCH MARK STAMPING: 0575 C 1981
DESIGNATION: 944 0575 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 8947
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Pipe embedded in ground OPUS PID:
LATITUDE: 46° 16.1' N ( 46.26830) LONGITUDE: 123° 49.6' W (-123.82700)
The bench mark is a disk braized onto the top of a pipe embedded into the
ground, 78 m (255 ft) NW of the centerline of U.S. Highway 401, 60.78 m (199.4
ft) SW of bench mark 0575 D 1981, 20.51 m (67.3 ft) south of the house with four
chimneys, 4.30 m (14.1 ft) NW of a tree, and 0.73 m (2.4 ft) NE of the corner
fence post for a 1 m (3 ft) high wooden fence, and 0.15 m (0.5 ft) below
ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9440575 PUBLICATION DATE: 08/09/2004
Name: KNAPPTON
WA
NOAA Chart: 18521 Latitude: 46° 16.1' N ( 46.26830)
USGS Quad: KNAPPTON Longitude: 123° 49.6' W (-123.82700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0575 D 1981
DESIGNATION: 944 0575 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 8948
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Pipe embedded in ground OPUS PID:
LATITUDE: 46° 16.1' N ( 46.26830) LONGITUDE: 123° 49.6' W (-123.82700)
The bench mark is a disk braized onto the top of a pipe embedded into the
ground, 22.77 m (74.7 ft) WSW of a garage on the property belonging to Mr.
Clarence Bell, 4.75 m (15.6 ft) WNW of the road to the garage, 0.88 m (2.9 ft)
NW of a telephone pole, and 0.15 m (0.5 ft) below the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9440575 PUBLICATION DATE: 08/09/2004
Name: KNAPPTON
WA
NOAA Chart: 18521 Latitude: 46° 16.1' N ( 46.26830)
USGS Quad: KNAPPTON Longitude: 123° 49.6' W (-123.82700)
T I D A L D A T U M S
Tidal datums at KNAPPTON based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: September 1981 - September 1981
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9439040 ASTORIA, TONGUE POINT, COLUMBIA RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.650
MEAN HIGH WATER MHW = 2.439
MEAN TIDE LEVEL MTL = 1.405
MEAN SEA LEVEL MSL = 1.399
MEAN LOW WATER MLW = 0.371
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
0575 A 1981 5.795 3.356
0575 B 1981 6.359 3.920
0575 C 1981 8.228 5.789
0575 D 1981 7.292 4.853
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9440575 PUBLICATION DATE: 08/09/2004
Name: KNAPPTON
WA
NOAA Chart: 18521 Latitude: 46° 16.1' N ( 46.26830)
USGS Quad: KNAPPTON Longitude: 123° 49.6' W (-123.82700)
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.