U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9454662 PUBLICATION DATE: 04/21/2003 Name: SNUG HARBOR, KNIGHT ISLAND AK NOAA Chart: 16700 Latitude: 60° 15.0' N ( 60.25000) USGS Quad: Seward (B-2) Longitude: 147° 43.0' W (-147.71700) To reach the tidal bench marks, from Cordova head north out of Orca Inlet to Orca Bay, continue west through Orca Bay to Prince William Sound, north of Green Island head SW to Snug Harbor. The tide station is located 1.3 km (0.7 nm) SW of Discovery Point. The bench marks were located in the vicinity along the shore. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 4662 B 1998 DESIGNATION: 945 4662 B MONUMENTATION: Tidal Station disk VM#: 15194 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 60° 14.4' N ( 60.24000) LONGITUDE: 147° 43.1' W (-147.71800) The primary bench mark is a disk located on a low wide rock area at the base of a steep 7 m (23 ft) high rock cliff, 47 m (155 ft) north (360 degrees magnetic) of bench mark 4662 C 1998, and 38 m (125 ft) SW (190 degrees magnetic) of bench mark 4662 A 1998. BENCH MARK STAMPING: 4662 A 1998 DESIGNATION: 945 4662 A MONUMENTATION: Tidal Station disk VM#: 15193 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 60° 14.4' N ( 60.24000) LONGITUDE: 147° 43.1' W (-147.71800) The bench mark is a disk set on top of a tall rock, 38 m (125 ft) NE (10 degrees magnetic) of bench mark 4662 B 1998, and approximatly 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: 9454662 PUBLICATION DATE: 04/21/2003 Name: SNUG HARBOR, KNIGHT ISLAND AK NOAA Chart: 16700 Latitude: 60° 15.0' N ( 60.25000) USGS Quad: Seward (B-2) Longitude: 147° 43.0' W (-147.71700) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 4662 C 1998 DESIGNATION: 945 4662 C MONUMENTATION: Tidal Station disk VM#: 15195 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 60° 14.4' N ( 60.24000) LONGITUDE: 147° 43.1' W (-147.71800) The bench mark is a disk set on a flat outcrop area close to the treeline, 47 m (155 ft) south (180 degrees magnetic) of bench mark 4662 B 1998, and 29 m (95 ft) NE (20 degrees magnetic) of bench mark 4662 D 1998. BENCH MARK STAMPING: 4662 D 1998 DESIGNATION: 945 4662 D MONUMENTATION: Tidal Station disk VM#: 15196 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 60° 14.4' N ( 60.24000) LONGITUDE: 147° 43.1' W (-147.71800) The bench mark is a disk set on top of a rock outcrop, 36 m (118 ft) NE (50 degrees magnetic) of bench mark 4662 E 1998, 29 m (95 ft) SW (200 degrees magnetic) of bench mark 4662 C 1998, and approximately 3 m (10 ft) high relative to the gravel beach to its south.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9454662 PUBLICATION DATE: 04/21/2003 Name: SNUG HARBOR, KNIGHT ISLAND AK NOAA Chart: 16700 Latitude: 60° 15.0' N ( 60.25000) USGS Quad: Seward (B-2) Longitude: 147° 43.0' W (-147.71700) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 4662 E 1998 DESIGNATION: 945 4662 E MONUMENTATION: Tidal Station disk VM#: 15197 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 60° 14.4' N ( 60.24000) LONGITUDE: 147° 43.1' W (-147.71800) The bench mark is a disk set on a flat surface on top of a 1 m x 1 m x 2 m (3 ft x 4 ft x 7 ft) rock, just south of a prominent rocky outcrop next to a gravel beach, and 36 m (118 ft) SW (330 degrees magnetic) of bench mark 4662 D 1998.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9454662 PUBLICATION DATE: 04/21/2003 Name: SNUG HARBOR, KNIGHT ISLAND AK NOAA Chart: 16700 Latitude: 60° 15.0' N ( 60.25000) USGS Quad: Seward (B-2) Longitude: 147° 43.0' W (-147.71700) T I D A L D A T U M S Tidal datums at SNUG HARBOR, KNIGHT ISLAND based on: LENGTH OF SERIES: 1 Month TIME PERIOD: September 1999 - September 1999 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9454050 CORDOVA, ORCA INLET, PRINCE WILLIAM SD Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 3.515 MEAN HIGH WATER MHW = 3.244 MEAN SEA LEVEL MSL = 1.876 MEAN TIDE LEVEL MTL = 1.846 MEAN LOW WATER MLW = 0.449 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 4662 B 1998 4.014 0.770 4662 A 1998 5.119 1.875 4662 C 1998 5.048 1.804 4662 D 1998 5.642 2.398 4662 E 1998 4.229 0.985
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9454662 PUBLICATION DATE: 04/21/2003 Name: SNUG HARBOR, KNIGHT ISLAND AK NOAA Chart: 16700 Latitude: 60° 15.0' N ( 60.25000) USGS Quad: Seward (B-2) Longitude: 147° 43.0' W (-147.71700) 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.