U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9462955 PUBLICATION DATE: 12/30/2014
Name: FALSE PASS, UNIMAK ISLAND
AK
NOAA Chart: 16535 Latitude: 54° 51.5' N ( 54.85830)
USGS Quad: FALSE PASS D-5 Longitude: 163° 24.4' W (-163.40700)
From the False Pass gravel airstrip, proceed NW 0.5 km (0.30 mi) along Unimak
Drive to its intersection with Mountain Valley Road, continue straight onto
Beach Road and proceed 1.23 km (0.76 mi) NNW to the city dock located east of
Isantoski Store. One bench mark is located within the Peter Pan Seafood s
Facility and the remaining bench marks are located along Unimak Drive and Beach
Road. The tide gauges were located 50 m (165 ft) from the beginning of the city
dock on the north side.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1 23
DESIGNATION: 946 2955 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 20888
AGENCY: US Coast and Geodetic Survey (USGS) IDB PID#:
SETTING CLASSIFICATION: Concrete Post OPUS PID#: BBFQ93
LATITUDE: 54° 51.3' N ( 54.85464) LONGITUDE: 163° 24.6' W (-163.40931)
The primary bench mark is a disk set in a 36-inch by 11-inch square concrete
post located in the Peter Pan Facility, 17.78 m (58.3 ft) SSE of SW corner of
the arctic entrance to a red wood-sided house labeled Hodiakoff , 14.56 m (47.8
ft) NE of SE corner of red wood-sided house labeled Yaponski , 6.87 m (22.5
ft) NW of centerline of 1.85 m (6.1 ft) wide wood boardwalk, 4.45 m (14.6 ft)
SW of SW corner of red wood-sided house labeled #1 , projecting 12 cm (0.4 ft)
above grade and 3 cm (0.1 ft) S of orange carsonite witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9462955 PUBLICATION DATE: 12/30/2014
Name: FALSE PASS, UNIMAK ISLAND
AK
NOAA Chart: 16535 Latitude: 54° 51.5' N ( 54.85830)
USGS Quad: FALSE PASS D-5 Longitude: 163° 24.4' W (-163.40700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2955 A 2013
DESIGNATION: 946 2955 A
MONUMENTATION: Metal Rod VM#: 20889
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod with sleeve OPUS PID:
LATITUDE: 54° 51.2' N ( 54.85311) LONGITUDE: 163° 24.8' W (-163.41269)
The bench mark is a stainless steel rod located north of the gravel airstrip,
61.85 m (202.9 ft) NW of a 15 mph speed limit sign, 58.90 m (193.2 ft) south of
telephone box #4, 20.65 m (67.7 ft) WSW of the centerline of Beach Drive, and
2.50 m (8.2 ft) ENE of an alder vegetation line. The datum point is set 8 cm
(0.3 ft) below grade, being the top of a stainless steel rod with a sleeve
driven 4.94 m (16.2 ft) to refusal, and encased in a 5-inch NOS logo cover.
BENCH MARK STAMPING: 2955 B 2013
DESIGNATION: 946 2955 B
MONUMENTATION: Metal Rod VM#: 20890
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod with sleeve OPUS PID#: BBDN10
LATITUDE: 54° 51.2' N ( 54.85392) LONGITUDE: 163° 24.8' W (-163.41347)
The bench mark is a stainless steel rod located north of the gravel airstrip,
48.85 m (160.3 ft) SSW of telephone box #3, 19.00 m (62.3 ft) SW of centerline
of Beach Road, 14.75 m (48.4 ft) SSE of centerline of private gravel driveway,
and 12.12 m (39.8 ft) NNW of alder vegetation line. The datum point is set 2.5
cm (0.1 ft) below grade, being the top of a stainless steel rod with a sleeve
driven 13.2 m (43.3 ft) to refusal, and encased in a 5-inch NOS logo cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9462955 PUBLICATION DATE: 12/30/2014
Name: FALSE PASS, UNIMAK ISLAND
AK
NOAA Chart: 16535 Latitude: 54° 51.5' N ( 54.85830)
USGS Quad: FALSE PASS D-5 Longitude: 163° 24.4' W (-163.40700)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2955 C 2013
DESIGNATION: 946 2955 C
MONUMENTATION: Metal Rod VM#: 20891
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod with sleeve OPUS PID:
LATITUDE: 54° 51.4' N ( 54.85603) LONGITUDE: 163° 24.9' W (-163.41561)
The bench mark is a stainless steel rod located north of the gravel airstrip,
42.05 m (138.0 ft) WSW of west corner of plywood-sided house, 40.81 m (133.9 ft)
north of the north corner of a white vinly-sided building, 30.30 m (99.4) ft NW
of a fire hydrant, 21.45 m (70.4 ft) SSE of edge of pronounced bluff, and 16.45
m (54.0 ft) WSW of centerline of Beach Road. The datum point is set 4 cm (0.1
ft) below grade, being the top of a stainless steel rod with a sleeve driven
9.73 m (31.9 ft) to refusal, and encased in a 5-inch NOS logo cover.
BENCH MARK STAMPING: 2955 D 2013
DESIGNATION: 946 2955 D
MONUMENTATION: Metal Rod VM#: 20892
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod with sleeve OPUS PID:
LATITUDE: 54° 51.5' N ( 54.85789) LONGITUDE: 163° 25.0' W (-163.41611)
The bench mark is a stainless steel rod located north of gravel airstrip, 62.50
m (205.1 ft) south of south corner of a metal sided shop, 57.73 m (189.4 ft) NNW
of grey wood utility box with a High Voltage sign, 55.31 m (181.5 ft) SSE of a
fire hydrant, 39.50 m (129.6 ft) SSW of Alaska Tidelands Survey 58 Cor 2 RP 1963
monument, and 17.21 m (56.5 ft) NE of centerline of Beach Road. The datum point
is set 5 cm (0.2 ft) below grade, being the top of a stainless steel rod with a
sleeve driven 8.50 m (27.9 ft) to refusal, and encased in a 5-inch NOS logo
cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9462955 PUBLICATION DATE: 12/30/2014
Name: FALSE PASS, UNIMAK ISLAND
AK
NOAA Chart: 16535 Latitude: 54° 51.5' N ( 54.85830)
USGS Quad: FALSE PASS D-5 Longitude: 163° 24.4' W (-163.40700)
T I D A L D A T U M S
Tidal datums at FALSE PASS, UNIMAK ISLAND based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: June 2014 - August 2014
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9462620 UNALASKA, DUTCH HARBOR
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 1.267
MEAN HIGH WATER MHW = 1.177
MEAN SEA LEVEL MSL = 0.745
MEAN TIDE LEVEL MTL = 0.720
MEAN LOW WATER MLW = 0.263
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1 23 2.228 1.051
2955 A 2013 5.495 4.318
2955 B 2013 5.534 4.357
2955 C 2013 5.060 3.883
2955 D 2013 3.910 2.733
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9462955 PUBLICATION DATE: 12/30/2014
Name: FALSE PASS, UNIMAK ISLAND
AK
NOAA Chart: 16535 Latitude: 54° 51.5' N ( 54.85830)
USGS Quad: FALSE PASS D-5 Longitude: 163° 24.4' W (-163.40700)
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.