U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
To reach the tidal station from the Deadhorse Airport located at 1 Airport Way
in Prudhoe Bay, AK, proceed by helicopter west-northwest for 155 km (96 mi) to
Cape Halkett on the west side of Harrison Bay. The tidal bench mark network is
set along the eastern coastline. The tide gauge sensors, consisting of a
pressure orifice and RBR, are located near the shore. The GNSS buoy sensor is
located 1.2 km (0.8 mi) offshore to the east in Harrison Bay.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6345 A 2025
DESIGNATION: 949 6345 A
MONUMENTATION: Tidal Station disk VM#: 25295
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: Disk set in ground screw OPUS PID#: BBKG87
LATITUDE: 70° 45.3' N ( 70.75547) LONGITUDE: 152° 20.5' W (-152.34084)
The primary tidal mark is a flange encased 3.5 inch AKDNR brass disk set in
level open tundra, 0.51 km (0.32 mi) ENE of tidal mark 949 6445 E, 105.87 m
(347.3 ft) east of tidal mark 949 6345 C, 75.44 m (247.5 ft) SE of tidal mark
949 6345 D, 68.17 m (223.7 ft) NE of tidal mark 949 6345 B and 63 m (206.7 ft)
WNW of the shoreline. The mark is set 5 cm (2 inches) below grade, epoxied to
the top of an 8 cm (3 inches) in diameter and 2 m (6.6 ft) long tapered
galvanized iron ground screw augered to a depth of 2.06 m (6.8 ft) and encased
in a 15 cm (6 inches) pvc collar with aluminum access lid.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6345 B 2025
DESIGNATION: 949 6345 B
MONUMENTATION: Tidal Station disk VM#: 25296
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: Disk set in a ground screw OPUS PID:
LATITUDE: 70° 45.3' N ( 70.75500) LONGITUDE: 152° 20.5' W (-152.34206)
The tidal mark is a flange encased 3.5 inch AKDNR brass disk set in level open
tundra, 0.45 km (0.28 mi) ENE of tidal mark 949 6345 E, 108.10 m (354.7 ft)
south of tidal mark 949 6345 D, 86 m (282.2 ft) WNW of the shoreline, 75.03 m
(246.2 ft) SE of tidal mark 949 6345 C and 68.17 m (223.7 ft) SW of tidal mark
949 6345 A. The mark is set 7 cm (3 inches) below grade, epoxied to the top of
an 8 cm (3 inches) in diameter and 2 m (6.6 ft) long tapered galvanized iron
ground screw augered to a depth of 2.08 m (6.8 ft) and encased in a 15 cm (6
inches) pvc collar with aluminum access lid.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6345 C 2025
DESIGNATION: 949 6345 C
MONUMENTATION: Tidal Station disk VM#: 25297
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: Disk set in a ground screw OPUS PID:
LATITUDE: 70° 45.3' N ( 70.75542) LONGITUDE: 152° 20.6' W (-152.34369)
The tidal mark is a flange encased 3.5 inch AKDNR brass disk set in level open
tundra, 0.42 km (0.26 mi) ENE of tidal mark 949 6345 E, 0.15 km (0.09 mi) WNW of
the shoreline, 105.87 m (347.3 ft) west of tidal mark 949 6345 A, 84.89 m (278.5
ft) SW of tidal mark 949 6345 D and 75.03 m (246.2 ft) NW of tidal mark 949 6345
B. The mark is set 1 cm (0 inch) below grade, epoxied to the top of an 8 cm (3
inches) in diameter and 2 m (6.6 ft) long tapered galvanized iron ground screw
augered to a depth of 2.02 m (6.6 ft) and encased in a 15 cm (6 inches) pvc
collar with aluminum access lid.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6345 D 2025
DESIGNATION: 949 6345 D
MONUMENTATION: Tidal Station disk VM#: 25298
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: Disk set in ground screw OPUS PID:
LATITUDE: 70° 45.4' N ( 70.75597) LONGITUDE: 152° 20.5' W (-152.34219)
The tidal mark is a flange encased 3.5 inch AKDNR brass disk set in level open
tundra, 0.50 km (0.31 mi) NE of tidal mark 949 6345 E, 130 m (426.5 ft) WNW of
the shoreline, 108.10 m (354.7 ft) north of tidal mark 949 6345 B, 84.89 m
(278.5 ft) NE of tidal mark 949 6345 C and 75.44 m (247.5 ft) NW of tidal mark
949 6345 A. The mark is set 6 cm (2 inches) below grade, epoxied to the top of
an 8 cm (3 inches) in diameter and 2 m (6.6 ft) long tapered galvanized iron
ground screw augered to a depth of 2.07 m (6.8 ft) and encased in a 15 cm (6
inches) pvc collar with aluminum access lid.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6345 E 2025
DESIGNATION: 949 6345 E
MONUMENTATION: Tidal Station disk VM#: 25299
AGENCY: AKDNR IDB PID#:
SETTING CLASSIFICATION: Disk set in ground screw OPUS PID#: BBKG88
LATITUDE: 70° 45.2' N ( 70.75344) LONGITUDE: 152° 21.2' W (-152.35330)
The tidal mark is a flange encased 3.5 inch AKDNR brass disk set in level open
tundra, 0.51 km (0.32 mi) WSW of tidal mark 949 6345 A, 0.50 km (0.31 mi) SW of
tidal mark 949 6345 D, 0.45 km (0.28 mi) WSW of tidal mark 949 6345 B, 0.42 km
(0.26 mi) WSW of tidal mark 949 6345 C and 0.41 km (0.25 mi) WNW of the
shoreline. The mark is set 5 cm (2 inches) below grade, epoxied to the top of
an 8 cm (3 inches) in diameter and 2 m (6.6 ft) long tapered galvanized iron
ground screw augered to a depth of 2.06 m (6.8 ft) and encased in a 15 cm (6
inches) pvc collar with aluminum access lid.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
T I D A L D A T U M S
Tidal datums at CAPE HALKETT based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: August 2025
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9497645 PRUDHOE BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.225
MEAN HIGH WATER MHW = 0.186
MEAN SEA LEVEL MSL = 0.115
MEAN TIDE LEVEL MTL = 0.105
MEAN LOW WATER MLW = 0.024
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum NAVD88 = -0.770
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6345 A 2025 1.080 0.894
6345 B 2025 0.926 0.740
6345 C 2025 1.383 1.197
6345 D 2025 1.105 0.919
6345 E 2025 1.427 1.241
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 9496345 PUBLICATION DATE: 04/13/2026
Name: CAPE HALKETT
AK
NOAA Chart: US4AK7LO Latitude: 70° 45.3' N ( 70.75508)
USGS Quad: HARRISON BAY D-4 SW Longitude: 152° 20.3' W (-152.33778)
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.