U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 9439069 PUBLICATION DATE: 01/23/2004
Name: KNAPPA
OR
NOAA Chart: 18523 Latitude: 46° 11.2' N ( 46.18670)
USGS Quad: KNAPPA Longitude: 123° 35.3' W (-123.58800)
To reach the tidal bench marks from Astoria, proceed 16.9 km (10.5 mi) east on
U.S. Highway 30 to Knappa Road, turn north onto Knappa Road for 0.3 km (0.2 mi)
around bend in road, then turn right onto Blind Slough Road and go 1.9 km (1.2
mi) north to a wooden bridge over railroad tracks; cross the bridge and continue
0.3 km (0.2 mi) north to the end of the road at Knappa Dock. The bench marks
are located along Knappa Dock Road, Waterhouse Road, and Knappa Plat Road. The
tide gage and staff were located about 152 m (500 ft) SW of Knappa Dock Road on
the pilings of a floating pier.
T I D A L B E N C H M A R K S
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 9439069 PUBLICATION DATE: 01/23/2004
Name: KNAPPA
OR
NOAA Chart: 18523 Latitude: 46° 11.2' N ( 46.18670)
USGS Quad: KNAPPA Longitude: 123° 35.3' W (-123.58800)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: J 31 1920
DESIGNATION: J 31
MONUMENTATION: Bench Mark disk VM#: 8885
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: SC0447
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 46° 11.2' N ( 46.18670) LONGITUDE: 123° 35.3' W (-123.58800)
The primary bench mark is a disk set in the top of a concrete monument located
near the railroad crossing at Waterhouse Road, 29.72 m (97.5 ft) west of bench
mark NO 3 1950, 14 m (45 ft) east of the centerline of Waterhouse Road, and 5 m
(15 ft) south of the centerline of the railroad tracks.
BENCH MARK STAMPING: NO 3 1950
DESIGNATION: 943 9069 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 8886
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete footing OPUS PID:
LATITUDE: 46° 11.2' N ( 46.18670) LONGITUDE: 123° 35.4' W (-123.59000)
The bench mark is a disk set vertically in the south face of the NW concrete
footing for the wooden located bridge over railroad tracks, 3 m (10 ft) north of
the centerline of the tracks, and 0.30 m (1 ft) above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 9439069 PUBLICATION DATE: 01/23/2004
Name: KNAPPA
OR
NOAA Chart: 18523 Latitude: 46° 11.2' N ( 46.18670)
USGS Quad: KNAPPA Longitude: 123° 35.3' W (-123.58800)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9069 A 1981
DESIGNATION: 943 9069 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 8887
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete vault OPUS PID:
LATITUDE: 46° 11.2' N ( 46.18670) LONGITUDE: 123° 35.4' W (-123.59000)
The bench mark is a disk set vertically in the SW corner of a 2 m (7 ft) wide x
5 m (16 ft) high abandoned concrete bank vault, 58 m (190 ft) north of the
centerline of the railroad tracks, 46 m (150 ft) NW of the NW corner of the
wooden bridge over railroad tracks, 18 m (60 ft) NW of the center of the
intersection of Knappa Dock Road and Waterhouse Road, and 2 m (6 ft) above the
ground.
BENCH MARK STAMPING: 9069 B 1981
DESIGNATION: 943 9069 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 8888
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Road OPUS PID#: BBCV68
LATITUDE: 46° 11.2' N ( 46.18670) LONGITUDE: 123° 35.4' W (-123.59000)
The bench mark is a disk located on the west side of Knappa Plat Road, 91 m (300
ft) south of the SW corner of the wooden bridge over railroad tracks on Knappa
Dock Road, 16.92 m (55.5 ft) SE of a red brick foundation of a residence, 2 m (6
ft) east of the centerline of a driveway to a private residence, 0.76 m (2.5 ft)
west of utility pole #PPL 0807 170905, 0.24 m (0.8 ft) below the ground, and
encased in a 4-inch PVC pipe.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 9439069 PUBLICATION DATE: 01/23/2004
Name: KNAPPA
OR
NOAA Chart: 18523 Latitude: 46° 11.2' N ( 46.18670)
USGS Quad: KNAPPA Longitude: 123° 35.3' W (-123.58800)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9069 C 1981
DESIGNATION: 943 9069 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 8889
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Road OPUS PID:
LATITUDE: 46° 11.2' N ( 46.18670) LONGITUDE: 123° 35.4' W (-123.59000)
The bench mark is a disk located on the west side of Knappa Plat Road, 148 m
(485 ft) south of the SW corner of the wooden bridge over railroad tracks on
Knappa Dock Road, 21 m (70 ft) NE of the NE corner of a private residence at
#525 Knappa Plat Road, 6.55 m (21.5 ft) west of the centerline of Knappa Plat
Road, 3.26 m (10.7 ft) NE of the NE corner of a concrete water meter box, 3 m
(10 ft) east of utility pole #PPL 0807 170901, 0.24 m (0.8 ft) below the ground,
and encased in a 4-inch PVC pipe.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 9439069 PUBLICATION DATE: 01/23/2004
Name: KNAPPA
OR
NOAA Chart: 18523 Latitude: 46° 11.2' N ( 46.18670)
USGS Quad: KNAPPA Longitude: 123° 35.3' W (-123.58800)
T I D A L D A T U M S
Tidal datums at KNAPPA based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: October 1981 - November 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 = 2.543
MEAN HIGH WATER MHW = 2.336
MEAN SEA LEVEL MSL = 1.330
MEAN TIDE LEVEL MTL = 1.320
MEAN LOW WATER MLW = 0.303
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
J 31 1920 4.639 2.303
NO 3 1950 4.103 1.767
9069 A 1981 6.789 4.453
9069 B 1981 23.114 20.778
9069 C 1981 25.007 22.671
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 9439069 PUBLICATION DATE: 01/23/2004
Name: KNAPPA
OR
NOAA Chart: 18523 Latitude: 46° 11.2' N ( 46.18670)
USGS Quad: KNAPPA Longitude: 123° 35.3' W (-123.58800)
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.