U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9458762 PUBLICATION DATE: 04/29/2004 Name: UNAVIKSHAK ISLAND AK NOAA Chart: 16566 Latitude: 56° 29.5' N ( 56.49170) USGS Quad: SUTWIK ISLAND (B-6) Longitude: 157° 44.4' W (-157.74000) To reach the tidal bench marks from Cape Kumliun on the Alaska Peninsula, go 5.6 km (3.5 mi) east to Unavikshak Island which is located 4.6 km (2.9 mi) NE of a small charted island. The tide gage and staff were located on the SW side of the Unavikshak island, below the southern-most of three hills. The bench marks were evenly spaced between two ledges pointing toward Cape Kumliun. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 8762 A 1997 DESIGNATION: 945 8762 A MONUMENTATION: Tidal Station disk VM#: 13711 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 56° 29.5' N ( 56.49170) LONGITUDE: 157° 44.4' W (-157.74000) The primary bench mark is a disk set flush in bedrock on the southern side of a prominent rock outcrop, 90 m (295 ft) NE of bench mark 8762 B 1997, 3 m (10 ft) from the cliff face, and 3 m (10 ft) above the high water line. BENCH MARK STAMPING: 8762 B 1997 DESIGNATION: 945 8762 B MONUMENTATION: Tidal Station disk VM#: 13712 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 56° 29.5' N ( 56.49170) LONGITUDE: 157° 44.4' W (-157.74000) The bench mark is a disk set flush in bedrock on a ledge, 90 m (295 ft) NE of bench mark 8762 C 1997, 5 m (16 ft) from the cliff face, and 2 m (7 ft) above the high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9458762 PUBLICATION DATE: 04/29/2004 Name: UNAVIKSHAK ISLAND AK NOAA Chart: 16566 Latitude: 56° 29.5' N ( 56.49170) USGS Quad: SUTWIK ISLAND (B-6) Longitude: 157° 44.4' W (-157.74000) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 8762 C 1997 DESIGNATION: 945 8762 C MONUMENTATION: Tidal Station disk VM#: 13713 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 56° 29.5' N ( 56.49170) LONGITUDE: 157° 44.4' W (-157.74000) The bench mark is a disk set flush in the NE corner of a rock outcrop, 70 m (230 ft) NE of bench mark 8762 D 1997, 2 m (5 ft) from the cliff face, and 1 m (3 ft) above the high water line. BENCH MARK STAMPING: 8762 D 1997 DESIGNATION: 945 8762 D MONUMENTATION: Tidal Station disk VM#: 13714 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock cliff ledge OPUS PID: LATITUDE: 56° 29.5' N ( 56.49170) LONGITUDE: 157° 44.4' W (-157.74000) The bench mark is a disk set flush in the base of a sloped cliff ledge, 100 m (328 ft) NE of bench mark 8762 E 1997, 2 m (7 ft) from the cliff face, and 0.50 m (1.6 ft) above the high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9458762 PUBLICATION DATE: 04/29/2004 Name: UNAVIKSHAK ISLAND AK NOAA Chart: 16566 Latitude: 56° 29.5' N ( 56.49170) USGS Quad: SUTWIK ISLAND (B-6) Longitude: 157° 44.4' W (-157.74000) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 8762 E 1997 DESIGNATION: 945 8762 E MONUMENTATION: Tidal Station disk VM#: 13715 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 56° 29.5' N ( 56.49170) LONGITUDE: 157° 44.4' W (-157.74000) The bench mark is a disk set flush in the northern-most outcrop of a cluster of prominent rock outcrops, 100 m (328 ft) SE of bench mark 8762 D 1997, 25 m (82 ft) from the cliff face, and 1 m (3 ft) below the high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9458762 PUBLICATION DATE: 04/29/2004 Name: UNAVIKSHAK ISLAND AK NOAA Chart: 16566 Latitude: 56° 29.5' N ( 56.49170) USGS Quad: SUTWIK ISLAND (B-6) Longitude: 157° 44.4' W (-157.74000) T I D A L D A T U M S Tidal datums at UNAVIKSHAK ISLAND based on: LENGTH OF SERIES: 2 MONTHS TIME PERIOD: July 1997 - August 1997 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9459450 SAND POINT, POPOF ISLAND Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 2.767 MEAN HIGH WATER MHW = 2.510 MEAN TIDE LEVEL MTL = 1.464 MEAN SEA LEVEL MSL = 1.435 MEAN LOW WATER MLW = 0.419 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 8762 A 1997 3.404 0.894 8762 B 1997 3.683 1.173 8762 C 1997 3.401 0.891 8762 D 1997 2.814 0.304 8762 E 1997 2.377 -0.133
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9458762 PUBLICATION DATE: 04/29/2004 Name: UNAVIKSHAK ISLAND AK NOAA Chart: 16566 Latitude: 56° 29.5' N ( 56.49170) USGS Quad: SUTWIK ISLAND (B-6) Longitude: 157° 44.4' W (-157.74000) 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.