U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
To reach the station from the north end of the I-5 Interstate Bridge across the
Columbia River at Vancouver, proceed north on I-5 1.0 km (0.6 mi) to Exit 1C-1D
for Mill Plain Blvd/WA-501/4th Plain Blvd, take the exit and keep right at the
fork to Exit 1C and continue north 0.2 km (0.1 mi) to the intersection with Mill
Plain Blvd/WA-501, turn left onto E Mill Plain Blvd and proceed west 0.2 km (0.1
mi) going under I-5, continue west 1.4 km (0.9 mi) on E 15th St, continue NW 1.3
km (0.8 mi) on W Mill Plain Blvd to WA-501 N / NW Lower River Rd, turn left onto
WA-501 N / NW Lower River Rd and proceed NW 5.3 km (3.3 mi) to the intersection
on the left, turn left to stay on NW Lower River Rd and proceed west 1.1 km (0.7
mi) to the hard bend to the north, continue north 6.5 km (4.0 mi) on NW Lower
River Rd to the locked gate across the road, continue north past the gate 1.0 km
(0.6 mi) to the tide station at the piling jetty on the left. The bench marks
are along the road from the gate to 0.2 km (0.1 mi) north of the tide station.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0171 A 2016
DESIGNATION: 944 0171 A
MONUMENTATION: Flange-encased Rod VM#: 22079
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 45° 44.0' N ( 45.73356) LONGITUDE: 122° 45.3' W (-122.75497)
The primary bench mark is a flange encased rod set in a field 1.1 km (0.7 mi)
past the gate at the end of NW lower river road, 72.50 m (237.9 ft) WNW of bench
mark vl-42, 64.75 m (212.4 ft) SSW of bench mark 944 0171 B, 61.05 m (200.3 ft)
west of the southern post of a gate, and 0.14 m (0.5 ft) ENE of a witness post.
The bench mark is set 2 cm (1 inch) below ground, being the top of a stainless
steel rod driven 22.66 m (74.3 ft) to refusal, in a sleeve extending to a depth
of 1.1 m (3.6 ft) , and encased in a 6-inch National Ocean Service logo cover
with kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0171 B 2016
DESIGNATION: 944 0171 B
MONUMENTATION: Flange-encased Rod VM#: 22080
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID#: BBFH21
LATITUDE: 45° 44.0' N ( 45.73414) LONGITUDE: 122° 45.3' W (-122.75472)
The bench mark is a flange encased rod set in a field 1.2 km (0.7 mi) past the
gate at the end of NW lower river road, 89.65 m (294.1 ft) SW of a utility pole,
74.5 m (244.4 ft) SW of the south wood post for a gate, 64.75 m (212.4 ft) NNE
of bench mark 944 0171 a, 56.65 m (185.9 ft) west of an underground utility
sign, 45.25 m (148.5 ft) west of the edge of pavement, and 0.15 m (0.5 ft) east
of a witness post. The datum point is set 14 cm (6 inches) below grade, being
the top of a stainless steel rod driven 20.35 m (66.8 ft) to refusal, in a
sleeve extending to a depth of 1.1 m (3.6 ft), and encased in a 6-inch (15 cm)
National Ocean Service logo cover with kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0171 C 2016
DESIGNATION: 944 0171 C
MONUMENTATION: Flange-encased Rod VM#: 22081
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 45° 44.1' N ( 45.73550) LONGITUDE: 122° 45.3' W (-122.75425)
The bench mark is a flange encased rod set in a field 1.3 km (0.8 mi) past the
gate at the end of NW lower river road, 53.72 m (176.2 ft) SSW of a power pole,
37.46 m (122.9 ft) NNE of a rock outcrop, 24.65 m (80.9 ft) east of the top of a
cut bank, 5.85 m (19.2 ft) west of the edge of pavement, 3.95 m (13.0 ft) west
of a witness post, and 3.85 m (12.6 ft) west of a wooden fence post. The datum
point is set 11 cm (4 inches) below ground being the top of a stainless steel
rod driven 18.29 m (60.0 ft) to refusal, in a sleeve extending to a depth of 1.1
m (3.6 ft), and encased in a 7-inch National Ocean Service logo cover with kick
block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: VL 42 1971
DESIGNATION: VL 42
MONUMENTATION: Survey disk VM#: 22082
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 45° 44.0' N ( 45.73336) LONGITUDE: 122° 45.2' W (-122.75408)
The bench mark is a disk set in a concrete monument in the right of way on the
east side of lower river road 1.1 km (0.7 mi) past the gate at the end of the
road, 72.50 m (237.9 ft) ESE of bench mark 944 0171 A, 38.50 m (126.3 ft) SSW of
the center wooden post for a gate, 11.62 m (38.1 ft) NE of a log gate post, 8.15
m (26.7 ft) west of a power pole, 0.57 m (1.9 ft) east of the edge of pavement,
0.45 m (1.5 ft) west of a witness post, and 0.21 m (0.7 ft) below grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: VL 40 1971
DESIGNATION: VL 40
MONUMENTATION: Survey disk VM#: 22083
AGENCY: USACE IDB PID#:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 45° 43.6' N ( 45.72742) LONGITUDE: 122° 45.2' W (-122.75403)
The bench mark is a disk set in a concrete monument in the right of way on the
east side of lower river road 0.4 km (0.2 mi) past the gate at the end of the
road, 24.01 m (78.8 ft) NNW of a power pole with metal tag marked
pudv1242765868, 16.33 m (53.6 ft) SW of the center trunk of a three trunk stump,
12.74 m (41.8 ft) ENE of the south wooden post of a gate, 3.49 m (11.5 ft) east
of the center line of the road, 1.07 m (3.5 ft) west of a metal witness post and
0.40 m (1.3 ft) below road level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
T I D A L D A T U M S
Tidal datums at KNAPP(THORNES)LNDG, WILLOW BAR based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: August 2016 - October 2016
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 = 0.959
MEAN HIGH WATER MHW = 0.797
MEAN TIDE LEVEL MTL = 0.440
MEAN SEA LEVEL MSL = 0.415
MEAN LOW WATER MLW = 0.082
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum NAVD88 = -2.125
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
0171 A 2016 6.377 5.580
0171 B 2016 8.410 7.613
0171 C 2016 6.470 5.673
VL 42 1971 6.418 5.621
VL 40 1971 6.423 5.626
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 9440171 PUBLICATION DATE: 12/29/2016
Name: KNAPP(THORNES)LNDG, WILLOW BAR
WA
NOAA Chart: 18525 Latitude: 45° 44.5' N ( 45.74170)
USGS Quad: SAUVIE ISLAND Longitude: 122° 45.3' W (-122.75500)
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.