U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9457407 PUBLICATION DATE: 09/05/2014
Name: NACHALNI ISLAND
AK
NOAA Chart: 16594 Latitude: 57° 58.7' N ( 57.97830)
USGS Quad: KODIAK D-3 ALASKA Longitude: 152° 55.5' W (-152.92500)
To reach the tidal bench marks from Port Lions, AK, by boat, start at the rock
jetty protecting the small boat harbor, and proceed for 6.95 km (3.75 nm)
heading towards the SE corner of Whale Island to 57 54'18.76"N, 152
45'45.43"W, then proceed through the pass for 13.2 km (7.1 nm) towards the south
end of Raspberry Island, then proceed 1.1 km (.57 nm) into the small bay
separating Raspberry Island from Nachalni Island. The bench marks are located on
the north side of Nachalni Island, set in bedrock along the beach, shore-side of
the vegetation and tree line. The tide gauge was installed approximately 400 m
(1,320 ft) to the north of the bench marks across the small bay at the obvious
rock outcrop on the beach on the southeast edge of Raspberry Island. The tide
staff was located on Nachalni Island.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: BM 2 1941
DESIGNATION: 945 7407 BM2
MONUMENTATION: Survey disk VM#: 15208
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge OPUS PID#: BBDP28
LATITUDE: 57° 58.8' N ( 57.97928) LONGITUDE: 152° 55.6' W (-152.92628)
The primary bench mark is a disk set flush in bedrock, located approximately
380.5 m (1,248.4 ft) SSE from the obvious rock outcropping on the beach across
the small bay, 37.56 m (123.23 ft) NE from bench mark 945 7404 D, and 7.58 m
(24.87 ft) north of the ledge and tree line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9457407 PUBLICATION DATE: 09/05/2014
Name: NACHALNI ISLAND
AK
NOAA Chart: 16594 Latitude: 57° 58.7' N ( 57.97830)
USGS Quad: KODIAK D-3 ALASKA Longitude: 152° 55.5' W (-152.92500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7407 A 1981
DESIGNATION: 945 7407 A
MONUMENTATION: Tidal Station disk VM#: 15210
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock Outcrop OPUS PID:
LATITUDE: 57° 58.7' N ( 57.97911) LONGITUDE: 152° 55.6' W (-152.92717)
The bench mark is a disk set flush in bedrock, located approximately 395.0 m
(1,296.0 ft) SE from the obvious rock outcrop on the beach across the bay, 19.16
m (62.86 ft) WSW from benchmark 945 7407 D, and 10.94 m (35.89 ft) north of the
ledge and tree line.
BENCH MARK STAMPING: 7407 B 1981
DESIGNATION: 945 7407 B
MONUMENTATION: Tidal Station disk VM#: 15211
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock Outcrop OPUS PID:
LATITUDE: 57° 58.7' N ( 57.97869) LONGITUDE: 152° 55.6' W (-152.92747)
The bench mark is a disk set flush in bedrock, located at the obvious ledge
above the beach, just below and under the vegetation and tree line, and 52.73 m
(172.99 ft) NNE from bench mark 945 7407 C.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9457407 PUBLICATION DATE: 09/05/2014
Name: NACHALNI ISLAND
AK
NOAA Chart: 16594 Latitude: 57° 58.7' N ( 57.97830)
USGS Quad: KODIAK D-3 ALASKA Longitude: 152° 55.5' W (-152.92500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7407 C 1981
DESIGNATION: 945 7407 C
MONUMENTATION: Tidal Station disk VM#: 15212
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock Outcrop OPUS PID:
LATITUDE: 57° 58.7' N ( 57.97833) LONGITUDE: 152° 55.7' W (-152.92803)
The bench mark is a disk set flush in a bedrock outcrop, located approximately
487.0 m (1,598.0 ft) SSE from the obvious rock outcrop on the beach across the
bay, 52.73 m (172.99 ft) SSW from bench mark 945 7407 B , and 9.65 m (31.66 ft)
WNW from the vegetation and tree line.
BENCH MARK STAMPING: 7407 D 2012
DESIGNATION: 945 7407 D
MONUMENTATION: Tidal Station disk VM#: 20584
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock Outcrop OPUS PID:
LATITUDE: 57° 58.7' N ( 57.97908) LONGITUDE: 152° 55.6' W (-152.92683)
The bench mark is a disk set flush in bedrock, approximately 393.0 m (1,289.0
ft) SE from the obvious rock outcrop on the beach across the bay, 37.56 m
(123.23 ft) SW from bench mark 945 7407 BM 2, 19.16 m (62.86 ft) east from bench
mark 945 7407 A, and 0.54 m (1.77 ft) north from the vegetation.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9457407 PUBLICATION DATE: 09/05/2014
Name: NACHALNI ISLAND
AK
NOAA Chart: 16594 Latitude: 57° 58.7' N ( 57.97830)
USGS Quad: KODIAK D-3 ALASKA Longitude: 152° 55.5' W (-152.92500)
T I D A L D A T U M S
Tidal datums at NACHALNI ISLAND based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: June 2014 - June 2014
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9457804 ALITAK, LAZY BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 4.166
MEAN HIGH WATER MHW = 3.908
MEAN TIDE LEVEL MTL = 2.224
MEAN SEA LEVEL MSL = 2.215
MEAN LOW WATER MLW = 0.541
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
BM 2 1941 3.887 -0.021
7407 A 1981 3.804 -0.104
7407 B 1981 5.109 1.201
7407 C 1981 4.544 0.636
7407 D 2012 5.253 1.345
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9457407 PUBLICATION DATE: 09/05/2014
Name: NACHALNI ISLAND
AK
NOAA Chart: 16594 Latitude: 57° 58.7' N ( 57.97830)
USGS Quad: KODIAK D-3 ALASKA Longitude: 152° 55.5' W (-152.92500)
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.