U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9450305 PUBLICATION DATE: 07/26/2004 Name: BOCA DE QUADRA AK NOAA Chart: 17434 Latitude: 55° 7.0' N ( 55.11670) USGS Quad: KETCHIKAN A-3 Longitude: 130° 47.9' W (-130.79800) To reach the tidal bench marks by plane or boat from the Gulf of Alaska, proceed east into the Dixon Entrance, then north to the Revillagigedo Channel, then NE into Boca de Quadra, and ESE of Orca Point. The bench marks are in the vicinity of an abandoned cannery north of Kestrel Island. The tide gage and staff were located west of the abandoned cannery. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 1 1933 DESIGNATION: 945 0305 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 9325 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 55° 7.0' N ( 55.11670) LONGITUDE: 130° 47.9' W (-130.79800) The primary bench mark is a disk set flush in an outcropping bedrock, 26 m (86 ft) due north (magnetic) of bench mark NO 2 1933, 0.6 m (2 ft) above the surrounding gravel and grass, and 0.6 m (2 ft) above the shoreline at the brushline.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9450305 PUBLICATION DATE: 07/26/2004 Name: BOCA DE QUADRA AK NOAA Chart: 17434 Latitude: 55° 7.0' N ( 55.11670) USGS Quad: KETCHIKAN A-3 Longitude: 130° 47.9' W (-130.79800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 2 1933 DESIGNATION: 945 0305 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 9326 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 55° 7.0' N ( 55.11670) LONGITUDE: 130° 47.9' W (-130.79800) The bench mark is a disk set flush in bedrock on a broad rocky point, 37 m (120 ft) NW (magnetic) of the northernmost group of piling ruins at the abandoned cannery site, and 19 m (61 ft) NNW from bench mark NO 3 1933. BENCH MARK STAMPING: NO 3 1933 DESIGNATION: 945 0305 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 9327 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 55° 7.0' N ( 55.11670) LONGITUDE: 130° 47.9' W (-130.79800) The bench mark is a disk set flush in bedrock on a broad rocky point, 35 m (115 ft) due west (magnetic) of bench mark 0305 A 1982, 17 m (56 ft) NW (magnetic) of the northernmost group of piling ruins at the abandoned cannery site, and 1 m (4 ft) above the shoreline.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9450305 PUBLICATION DATE: 07/26/2004 Name: BOCA DE QUADRA AK NOAA Chart: 17434 Latitude: 55° 7.0' N ( 55.11670) USGS Quad: KETCHIKAN A-3 Longitude: 130° 47.9' W (-130.79800) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 0305 A 1982 DESIGNATION: 945 0305 A TIDAL MONUMENTATION: Tidal Station disk VM#: 9328 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock dike OPUS PID: LATITUDE: 55° 7.0' N ( 55.11670) LONGITUDE: 130° 47.9' W (-130.79800) The bench mark is a disk set at the brushline in an exposed bedrock dike directly inshore from the northernmost group of piling ruins at the abandoned cannery site, and 2 m (5 ft) above the shoreline. BENCH MARK STAMPING: 0305 B 1982 DESIGNATION: 945 0305 B TIDAL MONUMENTATION: Tidal Station disk VM#: 9329 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Rocky island OPUS PID: LATITUDE: 55° 7.0' N ( 55.11670) LONGITUDE: 130° 47.9' W (-130.79800) The bench mark is a disk set in a small rocky island that is connected to marshland at low tide, and 32 m (106 ft) due west (magnetic) of bench mark NO 1 1933.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9450305 PUBLICATION DATE: 07/26/2004 Name: BOCA DE QUADRA AK NOAA Chart: 17434 Latitude: 55° 7.0' N ( 55.11670) USGS Quad: KETCHIKAN A-3 Longitude: 130° 47.9' W (-130.79800) T I D A L D A T U M S Tidal datums at BOCA DE QUADRA based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: October 1982 - October 1982 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 = 4.613 MEAN HIGH WATER MHW = 4.346 MEAN SEA LEVEL MSL = 2.409 MEAN TIDE LEVEL MTL = 2.407 MEAN LOW WATER MLW = 0.468 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 1933 5.346 1.000 NO 2 1933 5.487 1.141 NO 3 1933 4.588 0.242 0305 A 1982 5.620 1.274 0305 B 1982 3.949 -0.397
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9450305 PUBLICATION DATE: 07/26/2004 Name: BOCA DE QUADRA AK NOAA Chart: 17434 Latitude: 55° 7.0' N ( 55.11670) USGS Quad: KETCHIKAN A-3 Longitude: 130° 47.9' W (-130.79800) 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.