U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9454777 PUBLICATION DATE: 06/08/2011 Name: CHENEGA ISLAND (S.W. END) AK NOAA Chart: 16701 Latitude: 60° 17.0' N ( 60.28330) USGS Quad: Seward B-3 Longitude: 148° 6.8' W (-148.11300) T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 1 1957 DESIGNATION: 945 4777 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 14677 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Detached rock OPUS PID: LATITUDE: 60° 7.0' N ( 60.11670) LONGITUDE: 148° 6.8' W (-148.11300) The bench mark is a disk set in top of a detached rock on the east side of the southern-most bight of a small bay about one mile west of Chenega Village, about 40 m (131 ft) north of south end of ight and 10 m (33 ft) west of the approximate high water line. BENCH MARK STAMPING: NO 2 1957 DESIGNATION: 945 4777 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 13255 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 60° 7.0' N ( 60.11670) LONGITUDE: 148° 6.8' W (-148.11300) The bench mark is a disk set in top of a large boulder at the approximate high water line on the west side of the bight and about 15 m (49 ft) north of the south end of the bight.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9454777 PUBLICATION DATE: 06/08/2011 Name: CHENEGA ISLAND (S.W. END) AK NOAA Chart: 16701 Latitude: 60° 17.0' N ( 60.28330) USGS Quad: Seward B-3 Longitude: 148° 6.8' W (-148.11300) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 4 1964 DESIGNATION: 945 4777 TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 14678 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Black shale rock OPUS PID: LATITUDE: 60° 7.0' N ( 60.11670) LONGITUDE: 148° 6.8' W (-148.11300) The bench mark is a disk set in top of a black shale rock, 2.44 m (8.0 ft) inside moss line, and 2.44 m (8.0 ft) inshore from the approximate high water line. BENCH MARK STAMPING: NO 5 1964 DESIGNATION: 945 4777 TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 14679 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Black shale rock ledge OPUS PID: LATITUDE: 60° 7.0' N ( 60.11670) LONGITUDE: 148° 6.8' W (-148.11300) The bench mark is a disk set in top of a black shale rock ledge 1.22 m (4.0 ft) outside of a tree line, 22 m (72 ft) ENE of bench mark NO 4 1964, and 3 m (10 ft) inshore of the approximate high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9454777 PUBLICATION DATE: 06/08/2011 Name: CHENEGA ISLAND (S.W. END) AK NOAA Chart: 16701 Latitude: 60° 17.0' N ( 60.28330) USGS Quad: Seward B-3 Longitude: 148° 6.8' W (-148.11300) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 6 1964 DESIGNATION: 945 4777 TIDAL 6 MONUMENTATION: Tidal Station disk VM#: 14680 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Black shale ledge OPUS PID: LATITUDE: 60° 7.0' N ( 60.11670) LONGITUDE: 148° 6.8' W (-148.11300) The bench mark is a disk set in the top of a black shale ledge about 0.61 m (2.0 ft) outside of moss and tree line and 21.64 m (71.0 ft) ENE of bench mark NO 5 1964. BENCH MARK STAMPING: NO 7 1964 DESIGNATION: 945 4777 TIDAL 7 MONUMENTATION: Tidal Station disk VM#: 14681 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Outcrop of bedrock OPUS PID: LATITUDE: 60° 7.0' N ( 60.11670) LONGITUDE: 148° 6.8' W (-148.11300) The bench mark is a disk set in the top of a solid black prominent round outcrop of bedrock, on the south side of a small tree-topped islet ENE of bench mark NO 1 1957, 3 m (10 ft) outside of tree line and about 4.57 m (15.0 ft) inshore of approximate high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9454777 PUBLICATION DATE: 06/08/2011 Name: CHENEGA ISLAND (S.W. END) AK NOAA Chart: 16701 Latitude: 60° 17.0' N ( 60.28330) USGS Quad: Seward B-3 Longitude: 148° 6.8' W (-148.11300) T I D A L D A T U M S Tidal datums at CHENEGA ISLAND (S.W. END) based on: LENGTH OF SERIES: 57 Days TIME PERIOD: September 3 1996 - October 29 1996 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9454240 VALDEZ, PRINCE WILLIAM SOUND Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 3.601 MEAN HIGH WATER MHW = 3.327 MEAN SEA LEVEL MSL = 1.920 MEAN TIDE LEVEL MTL = 1.891 MEAN LOW WATER MLW = 0.455 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW NO 1 1957 5.158 1.831 NO 2 1957 5.337 2.010 NO 4 1964 5.013 1.686 NO 5 1964 4.855 1.528 NO 6 1964 5.395 2.068 NO 7 1964 5.268 1.941
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9454777 PUBLICATION DATE: 06/08/2011 Name: CHENEGA ISLAND (S.W. END) AK NOAA Chart: 16701 Latitude: 60° 17.0' N ( 60.28330) USGS Quad: Seward B-3 Longitude: 148° 6.8' W (-148.11300) 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.