U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 9452081 PUBLICATION DATE: 01/16/2025
Name: PORT SNETTISHAM, SPEEL RIVER ARM
AK
NOAA Chart: US5AK03M Latitude: 58° 7.0' N ( 58.11670)
USGS Quad: TAKU RIVER A-6 Longitude: 133° 41.4' W (-133.69000)
To reach the tide station from Juneau, AK, fly 55 km (34.2 mi) southeast to Port
Snettisham. From the north end of the runway at Port Snettisham proceed 245 m
(803.8 ft) south-southwest to a wooden dock on the western side of the runway.
The sensor and DCP are on the southwestern corner of the dock. The bench mark
network extends from the northwest side of the runway toward the tree line near
the hatchery.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2081 F 2024
DESIGNATION: 945 2081 F
MONUMENTATION: Flange-encased Rod VM#: 24926
AGENCY: AK DNR IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: BBJR76
LATITUDE: 58° 8.5' N ( 58.14164) LONGITUDE: 133° 44.0' W (-133.73331)
The primary bench mark is a flange encased rod set on a mossy 1.5 m (4.9 ft)
wide mound at the line of high tide that is south of the road to the hatchery
and just south of a grove of spruce trees, 173.6 m (569.6 ft) NE of the NE
corner of a two story tan wood frame building, 30.13 m (98.9 ft) south of the
centerline of the road and 3.85 m (12.6 ft) south of a 24 inch (61 cm) spruce
tree. The datum point is 10.0 cm (4 inches) below ground, being the top of a
stainless steel rod driven 7.6 m (24.9 ft) to refusal, in a sleeve extending to
a depth of 0.9 m (3.0 ft) (3.0 ft) and encased in a 7-inch (18 cm) AK DNR logo
cap with concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9452081 PUBLICATION DATE: 01/16/2025
Name: PORT SNETTISHAM, SPEEL RIVER ARM
AK
NOAA Chart: US5AK03M Latitude: 58° 7.0' N ( 58.11670)
USGS Quad: TAKU RIVER A-6 Longitude: 133° 41.4' W (-133.69000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2081 A 1997
DESIGNATION: 945 2081 A
MONUMENTATION: Tidal Station disk VM#: 13687
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete lamp post base OPUS PID:
LATITUDE: 58° 8.4' N ( 58.13953) LONGITUDE: 133° 43.9' W (-133.73131)
The bench mark is a disk set in the 0.6 m (2.0 ft) by 0.6 m (2.0 ft) concrete
base of a light pole, 73.0 m (239.5 ft) NW of a steel dolphin, 53.2 m (174.5 ft)
WSW of the westerly of the two light poles at the entrance to the barge landing,
19.8 m (65.0 ft) north of the NE corner of the covered walkway leading to the
floating dock, 4.7 m (15.4 ft) ENE of the centerline of the gravel road leading
to the floating dock and 2.1 m (6.9 ft) south of the SE corner of square utility
building 2.2 m (7.2 ft) wide.
BENCH MARK STAMPING: 2081 C 1997
DESIGNATION: 945 2081 C
MONUMENTATION: Tidal Station disk VM#: 13689
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 58° 8.3' N ( 58.13853) LONGITUDE: 133° 43.8' W (-133.73044)
The bench mark is a brass disk set in a 170 cm (67 inches) by 60 cm (24 inches)
by 50 cm (20 inches) exposed armor rock that is 1.5 m (4.9 ft) lower than the
road bed at the line of high high tide, 70.4 m (231.0 ft) east of the
southeastern most of the four steel piles for the floating dock, 52.6 m (172.6
ft) SSE of the steel dolphin, 37.1 m (121.7 ft) north of the grouping of piles
at the NW corner of the dock and 10.6 m (34.8 ft) west of the centerline of the
road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9452081 PUBLICATION DATE: 01/16/2025
Name: PORT SNETTISHAM, SPEEL RIVER ARM
AK
NOAA Chart: US5AK03M Latitude: 58° 7.0' N ( 58.11670)
USGS Quad: TAKU RIVER A-6 Longitude: 133° 41.4' W (-133.69000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2081 D 1997
DESIGNATION: 945 2081 D
MONUMENTATION: Tidal Station disk VM#: 13690
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID:
LATITUDE: 58° 8.3' N ( 58.13767) LONGITUDE: 133° 43.8' W (-133.73036)
The bench mark is a brass disk cemented in 80 cm (31 inches) by 80 cm (31
inches) by 20 cm (8 inches) exposed armor rock that 1.75 m (5.7 ft) lower than
the road bed and 1 m (3.3 ft) below high high tide, 25.1 m (82.3 ft) ESE of the
grouping of wood piles at the SW corner of the dock, 20.2 m (66.3 ft) WSW of the
centerline of the road, 16.97 m (55.7 ft) SSE of the south face of the wood dock
at high high water and 15.1 m (49.5 ft) SSW of a candy cane striped light pole
with a windsock.
BENCH MARK STAMPING: 2081 E 1997
DESIGNATION: 945 2081 E
MONUMENTATION: Tidal Station disk VM#: 13691
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Boulder OPUS PID#: BBJR75
LATITUDE: 58° 8.2' N ( 58.13722) LONGITUDE: 133° 43.8' W (-133.72983)
The bench mark is a brass disk cemented on a 1.4 m (4.6 ft) by 1.7 m (5.6 ft) by
1.5 m (4.9 ft) exposed armor rock that is 1.65 m (5.4 ft) lower than the roadbed
and 1 m (3.3 ft) below high high tide, located 272 m (892.4 ft) south of the
fish boundary sign on the west shore of the bay at the entrance to the fish
hatchery, 82.8 m (271.7 ft) west of the centerline of the runway, 64.3 m (211.0
ft) SE of the light pole with the windsock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9452081 PUBLICATION DATE: 01/16/2025
Name: PORT SNETTISHAM, SPEEL RIVER ARM
AK
NOAA Chart: US5AK03M Latitude: 58° 7.0' N ( 58.11670)
USGS Quad: TAKU RIVER A-6 Longitude: 133° 41.4' W (-133.69000)
T I D A L D A T U M S
Tidal datums at PORT SNETTISHAM, SPEEL RIVER ARM based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: May 2024 - July 2024
TIDAL EPOCH: 2012-2016
CONTROL TIDE STATION: 9452210 JUNEAU, GASTINEAU CHANNEL, STEPHENS PASS
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 4.629
MEAN HIGH WATER MHW = 4.335
MEAN TIDE LEVEL MTL = 2.366
MEAN SEA LEVEL MSL = 2.363
North American Vertical Datum NAVD88 = 0.764
MEAN LOW WATER MLW = 0.396
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2081 F 2024 5.526 1.191
2081 A 1997 7.181 2.846
2081 C 1997 5.443 1.108
2081 D 1997 4.763 0.428
2081 E 1997 5.486 1.151
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9452081 PUBLICATION DATE: 01/16/2025
Name: PORT SNETTISHAM, SPEEL RIVER ARM
AK
NOAA Chart: US5AK03M Latitude: 58° 7.0' N ( 58.11670)
USGS Quad: TAKU RIVER A-6 Longitude: 133° 41.4' W (-133.69000)
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.