U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) To reach the bench marks from Point Baker on the north tip of Prince of Wales Island via boat, proceed approximately northerly 32.8 km (17.7 nm) crossing Sumner Strait through Keku Straits to Devils Elbow, then proceed cautiously through Devils Elbow westerly and then northerly for 6.6 km (3.6 nm) to the area known as The Summit at the south end of Rocky Pass. The bench marks are on a group of three islands just west of the green daymark "27" at The Summit. The daymark is on the east tip of the northeasterly most of the three islands, on the west side of the dredged channel. The three islands are connected at about half tide. The tide gauges were established at the southwest corner of the southerly of the three islands (at the location of tidal bench mark 1 1929). Use extreme caution due to high currents and many rocks in this area. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 1 1929 DESIGNATION: 945 1349 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 18116 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Rock OPUS PID#: BBBG28 LATITUDE: 56° 40.9' N ( 56.68219) LONGITUDE: 133° 44.1' W (-133.73531) The primary bench mark is a disk set flush in the top of a rock about 2 m (7 ft) square and is on the SW corner of the south island, 190 m (623 ft) from the north point of the island that is west of the area across the channel and bearing 285 T (260 M), 59.0 m (193.6 ft) south of bench mark 945 1349 TIDAL 3, 38.35 m (125.8 ft) SW from bench mark 945 1349 TIDAL 2, approximately 5 m (16 ft) west of the tree line, and approximately 1.0 m (3.3 ft) above the apparent mean high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 2 1929 DESIGNATION: 945 1349 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 18117 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Rock OPUS PID: LATITUDE: 56° 40.9' N ( 56.68169) LONGITUDE: 133° 44.2' W (-133.73622) The bench mark is a disk set in the top of a rock about 2 m (7 ft) square, on the north side of the south island in a group that is about 230 m (755 ft) west of part of Keku Strait called The Summit, 50 m (164 ft) from bench mark 945 1349 TIDAL 4, 43.24 m (141.9 ft) SE of bench mark 945 1349 TIDAL 4, 38.35 m (125.8 ft) NE from bench mark 945 1349 TIDAL 1, 33.16 m (108.8 ft) SW from bench mark 945 1349 TIDAL 5, and approximately 1.5 m (4.9 ft) above the apparent mean high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 3 1929 DESIGNATION: 945 1349 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 18118 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: SETTING CLASSIFICATION: Rock OPUS PID: LATITUDE: 56° 40.9' N ( 56.68242) LONGITUDE: 133° 44.2' W (-133.73711) The bench mark is a disk set in the top of a large rock about 3 m (9 ft) square on the SW corner of the Northwest Island of a group that is about 230 m (755 ft) west of part of Keku Strait called The Summit the area consisting of a group of three islands (Northwest, East, and South) which are connected by a ledge at low water with Green daymark "27" set on the eastern ledge of the easternmost island, 59 m (194 ft) north of bench mark 945 1349 TIDAL 1, 17.24 m (56.7 ft) west of bench mark 945 1349 TIDAL 4, approximately 3 m (10 ft) SW from the tree line, approximately 2 m (6 ft) NE of mean high water line, and approximately 0.25 m (0.8 ft) above the apparent mean high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 1349 4 2006 DESIGNATION: 945 1349 TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 18119 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock OPUS PID: LATITUDE: 56° 40.9' N ( 56.68228) LONGITUDE: 133° 44.2' W (-133.73656) The bench mark is a disk set flush on a 1 m x 0.5 m (3.3 ft x 1.6 ft) rock on the SE corner of the NW island in a group that is about 200 m (656 ft) west of part of Keku Strait called The Summit the area consisting of a group of three islands (Northwest, East, and South) that are connected by a ledge at low water with Green daymark "27" set on the eastern ledge of the easternmost island, 58.12 m (190.7 ft) west of bench mark 945 1349 TIDAL 5, 43.24 m (141.9 ft) NW of bench mark 945 1349 TIDAL 2, 40 m (131.2 ft) from the tallest tree on the South Island bearing 160 T (135 M), 17.24 m (56.7 ft) east of bench mark 945 1349 TIDAL 3, 10 m (33 ft) NE of mean high water line, 2 m (6 ft) south of the tree line, and approximately 1.1 m (3.6 ft) above the apparent mean high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 1349 5 2006 DESIGNATION: 945 1349 TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 18120 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Rock OPUS PID: LATITUDE: 56° 40.9' N ( 56.68211) LONGITUDE: 133° 44.1' W (-133.73572) The bench mark is a disk set flush in a 3 m x 2 m (10 ft x 7 ft) rock on the SE corner of the east island in a group that is about 200 m (656 ft) west of part of Keku Strait called The Summit, the area consisting of a group of three islands (Northwest, East, and South) that are connected by a ledge at low water with Green daymark "27" set on the eastern ledge of the easternmost island, 58.12 m (190.7 ft) east of bench mark 945 1349 TIDAL 4, 45 m (148 ft) 235 T (210 M) of the tallest tree on the South Island, 33.16 m (108.8 ft) NE from bench mark 945 1349 TIDAL 5, 6.49 m (21.3 ft) north of the mean high water line, 5 m (16 ft) south of the treeline, and approximately 0.6 m (2 ft) above the apparent mean high water line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 6 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) T I D A L D A T U M S Tidal datums at THE SUMMIT, N.W. SUMMIT ISLAND based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: August 2007 - August 2007 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 = 4.631 MEAN HIGH WATER MHW = 4.365 MEAN SEA LEVEL MSL = 2.449 MEAN TIDE LEVEL MTL = 2.429 MEAN LOW WATER MLW = 0.492 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 1 1929 5.522 1.157 2 1929 5.948 1.583 3 1929 4.741 0.376 1349 4 2006 5.573 1.208 1349 5 2006 5.064 0.699
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 7 of 7 Station ID: 9451349 PUBLICATION DATE: 09/17/2008 Name: THE SUMMIT, N.W. SUMMIT ISLAND AK NOAA Chart: 17372 Latitude: 56° 40.9' N ( 56.68170) USGS Quad: PETERSBURG (C-9) Longitude: 133° 44.1' W (-133.73500) 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.