U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9451074 PUBLICATION DATE: 04/01/2004 Name: BUSHY ISLAND, SNOW PASSAGE AK NOAA Chart: 17382 Latitude: 56° 16.6' N ( 56.27670) USGS Quad: Petersburg (B-3) Longitude: 132° 59.1' W (-132.98500) To reach the tidal bench marks from Wrangell, navigate west out of Wrangell Harbor to Stikine Starit, continue south to Clarence Strait. Upon reaching Nesbitt Reef, head NW through Clarence Strait to Snow Passage, then 1.7 km (0.9 nm) west of the Fl 4s 22 ft 6M light to Bushy island. The tidal bench marks and tide station were located on the NW tip of the Bushy Island. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: DESIGNATION: 945 1074 BM 2 ALIAS: 2 1916 MONUMENTATION: Tidal Station disk VM#: 16165 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 56° 4.0' N ( 56.06670) LONGITUDE: 132° 28.7' W (-132.47800) The primary bench mark is a disk set in a bedrock on the NW lobe of Bushy Island, in the middle of a small point, NE of the mouth of a creek, 7.40 m (24.3 ft) north of the tree line, 5.40 m (17.7 ft) south of the apparent high water line, and 0.9 m (3 ft) above the apparent high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9451074 PUBLICATION DATE: 04/01/2004 Name: BUSHY ISLAND, SNOW PASSAGE AK NOAA Chart: 17382 Latitude: 56° 16.6' N ( 56.27670) USGS Quad: Petersburg (B-3) Longitude: 132° 59.1' W (-132.98500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: DESIGNATION: 945 1074 BM 3 ALIAS: 3 1916 MONUMENTATION: Tidal Station disk VM#: 16166 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 56° 4.0' N ( 56.06670) LONGITUDE: 132° 28.7' W (-132.47800) The bench mark is a disk set flush on a grey/white granite boulder of approximate size 2 m x 2 m (7 ft x 5 ft) which is the only light colored boulder in the area, positioned west of a creek located on the NW lobe of Bushy Island, 6.50 m (21.3 ft) from the tree line, and 0.21 m (0.7 ft) above the apparent high water line. BENCH MARK STAMPING: 1074 B 2000 DESIGNATION: 945 1074 B MONUMENTATION: Tidal Station disk VM#: 16167 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 56° 4.0' N ( 56.06670) LONGITUDE: 132° 28.7' W (-132.47800) The bench mark is a disk set flush in a rock outcrop, west of a creek on the NW lobe of Bushy Island, 18 (59 ft) north of the tree line, 0.50 m (1.6 ft) south of the apparent high water line, and 0.40 m (1.3 ft) above the apparent high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9451074 PUBLICATION DATE: 04/01/2004 Name: BUSHY ISLAND, SNOW PASSAGE AK NOAA Chart: 17382 Latitude: 56° 16.6' N ( 56.27670) USGS Quad: Petersburg (B-3) Longitude: 132° 59.1' W (-132.98500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 1074 C 2000 DESIGNATION: 945 1074 C MONUMENTATION: Tidal Station disk VM#: 16168 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 56° 4.0' N ( 56.06670) LONGITUDE: 132° 28.7' W (-132.47800) The bench mark is a disk set in a bedrock located west of a creek on the NW lobe of Bushy Island, 6.40 m (21.0 ft) from the tree line, 1.30 m (4.3 ft) from the apparent high water line, and 0.20 m (0.7 ft) above the apparent high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9451074 PUBLICATION DATE: 04/01/2004 Name: BUSHY ISLAND, SNOW PASSAGE AK NOAA Chart: 17382 Latitude: 56° 16.6' N ( 56.27670) USGS Quad: Petersburg (B-3) Longitude: 132° 59.1' W (-132.98500) T I D A L D A T U M S Tidal datums at BUSHY ISLAND, SNOW PASSAGE based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: April 2000 - April 2000 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9450460 KETCHIKAN, TONGASS NARROWS Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 4.492 MEAN HIGH WATER MHW = 4.228 MEAN TIDE LEVEL MTL = 2.336 MEAN SEA LEVEL MSL = 2.305 MEAN LOW WATER MLW = 0.445 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 945 1074 BM 2 5.717 1.489 945 1074 BM 3 5.006 0.778 1074 B 2000 5.044 0.816 1074 C 2000 5.272 1.044
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9451074 PUBLICATION DATE: 04/01/2004 Name: BUSHY ISLAND, SNOW PASSAGE AK NOAA Chart: 17382 Latitude: 56° 16.6' N ( 56.27670) USGS Quad: Petersburg (B-3) Longitude: 132° 59.1' W (-132.98500) 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.