U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
To reach the tidal bench marks from Seldovia Airport, follow Airport Avenue
which will become Main Street, continue on Main Street to Dock Street, turn left
on Dock Street and continue onto the dock to the last building (Seldovia Fuel
and Lube) on the left. The bench marks are in the general vicinity. The tide
gauge is located in a small room in the NE corner of the Seldovia Fuel and Lube
building. To reach the tide station by ferry, the ferry will dock at the same
dock where the tide gauge is located.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5500 B 1982
DESIGNATION: 945 5500 B
MONUMENTATION: Tidal Station disk VM#: 1311
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 59° 26.5' N ( 59.44111) LONGITUDE: 151° 43.1' W (-151.71753)
The primary bench mark is a disk set in bedrock located in a 2 m x 3 m (5 ft x
10 ft) rocky outcropping located in the NW corner of the property at 320 Main
Street, 27 m (89 ft) N of the intersection of Dock Street and Main Street, 14 m
(45 ft) NNW of utility pole # U2 31 7035, 9 m (30 ft) ENE of the centerline of
Main Street, 4 m (14 ft) ENE of the E side of Main Street, 3.13 m (10.3 ft) E of
the first spruce tree S of this driveway along Main Street, 2.70 m (8.8 ft) NE
of the second tree S of the driveway along Main Street, and 2 m (6 ft) above
street level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 20 1968
DESIGNATION: 945 5500 TIDAL 20
MONUMENTATION: Tidal Station disk VM#: 1303
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete bull rail OPUS PID:
LATITUDE: 59° 26.4' N ( 59.44044) LONGITUDE: 151° 43.2' W (-151.72003)
The bench mark is a disk set flush in the south bull rail at the approach part
of the City Pier (fuel pier) in Seldovia Harbor, 19.96 m (65.5 ft) W of the E
end of the bumper rail, 0.61 m (2.0 ft) E of the tide house door, 0.25 m (0.8
ft) NW of the most westerly one of the seven steel posts supporting a guard
rail, 0.22 m (0.7 ft) NE of the NE corner of the Seldovia Fuel & Lube's dock
house, and 0.25 m (0.8 ft) above the road.
BENCH MARK STAMPING: 5500 A 1982
DESIGNATION: 945 5500 A
MONUMENTATION: Tidal Station disk VM#: 1310
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 59° 26.5' N ( 59.44144) LONGITUDE: 151° 43.0' W (-151.71736)
The bench mark is a disk set in bedrock located at the S edge of a 61 m (200 ft)
high rocky cliff which runs in a N-S direction 2 m (6 ft) above street level
(base), 48 m (158 ft) NE of the E side of the foundation of the demolished John
Cabot Company, 42 m (137 ft) N of bench mark 945 5500 B, 34 m (111 ft) E of
yellow fire plug, and 3.29 m (10.8 ft) E of an orange fiberglass witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5500 C 1982
DESIGNATION: 945 5500 C
MONUMENTATION: Tidal Station disk VM#: 1312
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 59° 26.4' N ( 59.43922) LONGITUDE: 151° 43.1' W (-151.71861)
The bench mark is a disk set in bedrock located in the base of the southern edge
of a rocky cliff, 31 m (103 ft) NE of the SE corner of the Main Street Market,
17 m (57 ft) NW of the NW corner of a building located approximately 5 m (16 ft)
above the street at 274 Main Street, 7.04 m (23.1 ft) NE of the centerline of
Main Street, 1.13 m (3.7 ft) NE of an orange fiberglass witness post, and 1 m (3
ft) above ground level.
BENCH MARK STAMPING: 5500 D 1987
DESIGNATION: 945 5500 D
MONUMENTATION: Tidal Station disk VM#: 1313
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Pavement OPUS PID:
LATITUDE: 59° 26.4' N ( 59.43986) LONGITUDE: 151° 43.1' W (-151.71750)
The bench mark is a disk located in the sill of a steel roll-up door on the N
side of the Native Corporation building at 238 Main Street, 31 m (102 ft) S of a
light pole, 0.21 m (0.7 ft) E of the W side of a 3 m x 6 m (10 ft x 20 ft) steel
roll-up door, and 0.15 m (0.5 ft) N of the door.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 945 5500 G 2014
DESIGNATION: 945 5500 G
MONUMENTATION: Bench Mark disk VM#: 21254
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Abutment of a bridge OPUS PID:
LATITUDE: 59° 26.4' N ( 59.44078) LONGITUDE: 151° 43.3' W (-151.72086)
Bench mark is a disk set at the NW end of the Seldovia city dock in the NW
corner in the top of a 2.5 m (8.2 ft) x 2.1 m (6.9 ft) x 0.23 m (0.8 ft) high
concrete pad supporting a metal light pole and small wooden shed. 7.22 m (23.7
ft) WNW of a yellow bollard, 5.58 m (18.3 ft) E of a red bollard, 1.0 m (3.3 ft)
WNW of a 25 cm (10 inches) diameter steel pipe set into the same concrete pad.
BENCH MARK STAMPING: 945 5500 H 2014
DESIGNATION: 945 5500 H
MONUMENTATION: Bench Mark disk VM#: 21255
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Concrete Foundation OPUS PID:
LATITUDE: 59° 26.4' N ( 59.44050) LONGITUDE: 151° 43.1' W (-151.71825)
Bench mark is a disk set in the top of a concrete door foundation at the S side
of the W facing garage door of the Seldovia fuel and lube building, 25.5 m (83.7
ft) SE of a fire hydrant located on the N side of ferry dock road,19.9 m (65.3
ft) E of a 1.04 m (3.4 ft) high loading dock, 0.1 m N of the door opening.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 945 5500 J 2014
DESIGNATION: 945 5500 J
MONUMENTATION: Bench Mark disk VM#: 21256
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Concrete light base OPUS PID:
LATITUDE: 59° 26.4' N ( 59.44042) LONGITUDE: 151° 43.1' W (-151.71772)
Bench mark is a disk set into the top of a concrete base supporting a galvanized
light stanchion approximately 15 m (49.2 ft) S of the Seldovia fuel and lube
building. 22.6 m (74.1 ft) NW of a fire hydrant near the W side of main street,
8.1 m (26.6 ft) W of a cable utility box marked 1a4, 0.46 m (1.5 ft) above
grade.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: Terra Surveys SH USA 199
DESIGNATION: Terra Surveys 199
MONUMENTATION: Bench Mark disk VM#: 21733
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Surface disk set in state pier OPUS PID:
LATITUDE: 59° 26.5' N ( 59.44083) LONGITUDE: 151° 43.3' W (-151.72094)
The bench mark is a disk set at the NW end of the Seldovia city dock in the NW
corner 1 m (3.3 ft) NE of a 2.5 m (8.2 ft) x 2.1 m (6.9 ft) x 0.23 m (0.8 ft)
high concrete pad supporting a metal light pole and small wooden shed, 8.22 m
(23.7 ft) WNW of a yellow bollard, 7.58 m (18.3 ft) E of a red bollard, 1 m (3.3
ft) SE of the NW end of the pier.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
T I D A L D A T U M S
Tidal datums at SELDOVIA, COOK INLET based on:
LENGTH OF SERIES: 19 YEARS
TIME PERIOD: Jan '83 - Dec '01 & Jan '12 - Dec '16
TIDAL EPOCH: 2012-2016
CONTROL TIDE STATION:
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (10/15/1966) = 7.808
MEAN HIGHER HIGH WATER MHHW = 5.499
MEAN HIGH WATER MHW = 5.252
MEAN SEA LEVEL MSL = 2.912
MEAN TIDE LEVEL MTL = 2.884
MEAN LOW WATER MLW = 0.517
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (12/15/2016) = -2.017
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
5500 B 1982 11.263 6.011
NO 20 1968 9.164 3.912
5500 A 1982 11.259 6.007
5500 C 1982 9.771 4.518
5500 D 1987 9.763 4.511
945 5500 G 2014 9.325 4.073
945 5500 H 2014 9.801 4.549
945 5500 J 2014 9.857 4.605
Terra Surveys SH USA 199 9.051 3.799
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
Foot Notes:
Certain geographic areas are experiencing rapid land movement due to uplift or
subsidence, which results in anomalous relative sea level trends compared to
most other coastal regions in the United States
(http://tidesandcurrents.noaa.gov/sltrends/index.shtml). In these areas, NOAA
has adopted a modified procedure for computing accepted tidal datums for the
National Water Level Observation Network (NWLON). The long-term control stations
in these areas have tidal datums reviewed approximately every 5 years, and if
they meet the criteria for an update, the 5-year period used for the modified
procedure will be listed in the Time Period section for the datums. The adoption
of this procedure was necessary to ensure that these tidal datums accurately
represent the existing stand of sea level relative to the land. A detailed
report explaining this modified procedure can be found in the publications
section of the CO-OPS Tides & Currents website at
http://tidesandcurrents.noaa.gov/pub.html.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 9 of 9
Station ID: 9455500 PUBLICATION DATE: 02/16/2018
Name: SELDOVIA, COOK INLET
AK
NOAA Chart: 16646 Latitude: 59° 26.4' N ( 59.44053)
USGS Quad: SELDOVIA B-5 Longitude: 151° 43.2' W (-151.71994)
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.