U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9451909 PUBLICATION DATE: 07/15/2004 Name: GOOD ISLAND, GAMBIER BAY AK NOAA Chart: 17362 Latitude: 57° 29.2' N ( 57.48670) USGS Quad: SUMDUM (B-6) Longitude: 133° 53.9' W (-133.89800) To reach the tidal bench marks, follow the eastern shore of Good Island about 100 m (328 ft) SE of the most northern point, there are three small ledges which are approximately 2 m (7 ft) above the apparent high water line and have rocky beaches between them, the most northern outcrop is just south of a sheer-faced rock which gently slopes downward toward the sea in a NE direction. The bench marks were located on those ledges, and the tide gauge was located in the vicinity. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 1909 A 1995 DESIGNATION: 945 1909 A MONUMENTATION: Tidal Station disk VM#: 13603 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 57° 29.2' N ( 57.48670) LONGITUDE: 133° 53.9' W (-133.89800) The primary bench mark is a disk set in the most southern of the three 2 m (7 ft) high rock outcrops which is covered in lichen and slopes downward, parallel to the waterline, 21 m (69 ft) SE (100 degrees magnetic) to bench mark 2 1920, and 2 m (7 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: 9451909 PUBLICATION DATE: 07/15/2004 Name: GOOD ISLAND, GAMBIER BAY AK NOAA Chart: 17362 Latitude: 57° 29.2' N ( 57.48670) USGS Quad: SUMDUM (B-6) Longitude: 133° 53.9' W (-133.89800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 1909 B 1995 DESIGNATION: 945 1909 B MONUMENTATION: Tidal Station disk VM#: 13604 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 57° 29.2' N ( 57.48670) LONGITUDE: 133° 53.9' W (-133.89800) The bench mark is a disk set in a flat ledge of a bedrock outcrop 0.5 m (1.7 ft) high at the tree line, between the most northern and the center outcrop. 21.70 m (71.2 ft) NW (300 degrees magnetic) from bench mark 2 1920. BENCH MARK STAMPING: 1909 C 1995 DESIGNATION: 945 1909 C MONUMENTATION: Tidal Station disk VM#: 13605 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 57° 29.2' N ( 57.48670) LONGITUDE: 133° 53.9' W (-133.89800) The bench mark is a disk set atop the most northern rock outcrop, 17.50 m (57.4 ft) NW (335 degrees magnetic) from bench mark 1909 B 1995, about 1 m (5 ft) seaward of the tree line, and about 1 m (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: 9451909 PUBLICATION DATE: 07/15/2004 Name: GOOD ISLAND, GAMBIER BAY AK NOAA Chart: 17362 Latitude: 57° 29.2' N ( 57.48670) USGS Quad: SUMDUM (B-6) Longitude: 133° 53.9' W (-133.89800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 1 DESIGNATION: 945 1909 TIDAL 1 ALIAS: 1 1920 MONUMENTATION: Tidal Station disk VM#: 13606 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 57° 29.2' N ( 57.48670) LONGITUDE: 133° 53.9' W (-133.89800) The bench mark is a disk set flush in top of a small fat-topped 0.46 m (1.5 ft) high rock on the NE side of Good Island, 101 m (330 ft) SE of most northern point of the island, 12 m (40 ft) from the apparent high water line, and 3 m (10 ft) back from the timber line. BENCH MARK STAMPING: 2 DESIGNATION: 945 1909 TIDAL 2 ALIAS: 2 1920 MONUMENTATION: Tidal Station disk VM#: 13607 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 57° 29.2' N ( 57.48670) LONGITUDE: 133° 53.9' W (-133.89800) The bench mark is a disk set in top of a small triangular-shaped about 0.46 m (1.5 ft) high boulder on NE side of the island, 101 m (331 ft) SE of the most northern part of the island, 6 m (20 ft) east of bench mark 2 1920, 6 m (20 ft) from the apparent high water line, and 3 m (10 ft) from tree line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9451909 PUBLICATION DATE: 07/15/2004 Name: GOOD ISLAND, GAMBIER BAY AK NOAA Chart: 17362 Latitude: 57° 29.2' N ( 57.48670) USGS Quad: SUMDUM (B-6) Longitude: 133° 53.9' W (-133.89800) T I D A L D A T U M S Tidal datums at GOOD ISLAND, GAMBIER BAY based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: April 1995 - May 1995 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 = 4.649 MEAN HIGH WATER MHW = 4.357 MEAN SEA LEVEL MSL = 2.438 MEAN TIDE LEVEL MTL = 2.411 MEAN LOW WATER MLW = 0.465 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 1909 A 1995 6.122 1.765 1909 B 1995 5.602 1.244 1909 C 1995 5.818 1.460 1 7.015 2.657 2 5.816 1.459
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9451909 PUBLICATION DATE: 07/15/2004 Name: GOOD ISLAND, GAMBIER BAY AK NOAA Chart: 17362 Latitude: 57° 29.2' N ( 57.48670) USGS Quad: SUMDUM (B-6) Longitude: 133° 53.9' W (-133.89800) 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.