U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9451263 PUBLICATION DATE: 11/13/2003 Name: POINT LOCKWOOD, WRANGELL NARROWS AK NOAA Chart: 17375 Latitude: 56° 33.5' N ( 56.55830) USGS Quad: PETERSBURG (C-3) Longitude: 132° 57.8' W (-132.96300) To reach the tidal bench marks from the Petersburg, Alaska, South Harbor public boat launch, proceed 16.0 km (8.7 nm) south down Wrangell Narrows past Papke's Landing state warf, continue 4.6 km (2.5 nm) south past Anchor Point, continue 10.1 km (5.6 nm) south past Beecher Pass . The Point Lockwood tide gauge was located in a small cove, immediately north of the Point Lockwood beacon. The tidal bench marks are located in the rock outcrop on shore. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 2 1925 DESIGNATION: 945 1263 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 17234 AGENCY: US Coast & Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 56° 33.5' N ( 56.55830) LONGITUDE: 132° 58.0' W (-132.96700) The bench mark is a disk set in top of small rock shelf on northerly side of first rock outcrop, 69 m (225 ft) south of bench mark NO 1 1925, immediately north of cobble beaches on north side of Point Lockwood, and 3.54 m (11.6 ft) NW of bench mark 1263 A 2003.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9451263 PUBLICATION DATE: 11/13/2003 Name: POINT LOCKWOOD, WRANGELL NARROWS AK NOAA Chart: 17375 Latitude: 56° 33.5' N ( 56.55830) USGS Quad: PETERSBURG (C-3) Longitude: 132° 57.8' W (-132.96300) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 1 1925 DESIGNATION: 945 1263 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 17235 AGENCY: US Coast & Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 56° 33.5' N ( 56.55830) LONGITUDE: 132° 58.0' W (-132.96700) The bench mark is a disk set in top of boulder, 2 m x 2m x 1 m (5 ft x 5 ft x 3 ft) high which is on shore of first cove north of Point Lockwood, 91 m (300 ft) south of stream into head of this cove, 69 m (225 ft) north of bench mark NO 2 1925, and 3.14 m (10.3 ft) SW of bench mark NO 3 1929. BENCH MARK STAMPING: NO 3 1929 DESIGNATION: 945 1263 TIDAL 3 MONUMENTATION: Reference Mark disk VM#: 17236 AGENCY: US Coast & Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Granite boulder OPUS PID: LATITUDE: 56° 33.5' N ( 56.55830) LONGITUDE: 132° 58.0' W (-132.96700) The bench mark is a reference mark disk set in well-embedded flat granite boulder measuring 2 m x 1 m (5 ft x 3 ft), the boulder is in grass, 3.14 m (10.3 ft) NE of bench mark NO 1 1925, and 3 m (10 ft) from tree line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9451263 PUBLICATION DATE: 11/13/2003 Name: POINT LOCKWOOD, WRANGELL NARROWS AK NOAA Chart: 17375 Latitude: 56° 33.5' N ( 56.55830) USGS Quad: PETERSBURG (C-3) Longitude: 132° 57.8' W (-132.96300) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 1263 A 2003 DESIGNATION: 945 1263 A MONUMENTATION: Tidal Station disk VM#: 17237 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 56° 33.5' N ( 56.55830) LONGITUDE: 132° 58.0' W (-132.96700) The bench mark is a disk set in small level rock ledge, 3.54 m (11.6 ft) SE of bench mark NO 2 1925, and 1 m (4 ft) SE of "x" chiseled in rock at apparent high water line facing Wrangell Narrows immediately NW of cobble beaches on north side of Point Lockwood. BENCH MARK STAMPING: 1263 B 2003 DESIGNATION: 945 1263 B MONUMENTATION: Tidal Station disk VM#: 17238 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Schist rock outcrop OPUS PID: LATITUDE: 56° 33.4' N ( 56.55670) LONGITUDE: 132° 57.9' W (-132.96500) The bench mark is a disk set in prominent schist bedrock outcrop located at apparent high water line in the SE corner of the first small cobble beach NW of the north side of Point Lockwood, and about 1 m (3 ft) above beach level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9451263 PUBLICATION DATE: 11/13/2003 Name: POINT LOCKWOOD, WRANGELL NARROWS AK NOAA Chart: 17375 Latitude: 56° 33.5' N ( 56.55830) USGS Quad: PETERSBURG (C-3) Longitude: 132° 57.8' W (-132.96300) T I D A L D A T U M S Tidal datums at POINT LOCKWOOD, WRANGELL NARROWS based on: LENGTH OF SERIES: 2 MONTHS TIME PERIOD: August 2003 - September 2003 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 = 4.599 MEAN HIGH WATER MHW = 4.330 MEAN TIDE LEVEL MTL = 2.400 MEAN SEA LEVEL MSL = 2.355 MEAN LOW WATER MLW = 0.469 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 2 1925 5.146 0.815 NO 1 1925 5.219 0.889 NO 3 1929 5.132 0.802 1263 A 2003 4.254 -0.076 1263 B 2003 5.310 0.980
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9451263 PUBLICATION DATE: 11/13/2003 Name: POINT LOCKWOOD, WRANGELL NARROWS AK NOAA Chart: 17375 Latitude: 56° 33.5' N ( 56.55830) USGS Quad: PETERSBURG (C-3) Longitude: 132° 57.8' W (-132.96300) 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.