U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9450296 PUBLICATION DATE: 07/14/2010 Name: CUSTOM HOUSE COVE, MARY ISLAND AK NOAA Chart: 17424 Latitude: 55° 6.0' N ( 55.10000) USGS Quad: KETCHIKAN A-4 Longitude: 131° 13.0' W (-131.21700) To reach the benchmarks by boat from Ketchikan, AK, proceed SE through Tongass Narrows into Revillagigedo Channel, then continue ESE for 22.2 km (12.0 nm) to Hog Rocks, then head SSE 9.3 km (5.0 nm) to Custom House Cove. Custom House Cove is on the west side of Mary Island. The site is located on the west side of the island, on the eastern shore of Custom House Cove immediately south of a small rock islet. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 0296 A 2010 DESIGNATION: 945 0296 A MONUMENTATION: Tidal Station disk VM#: 19627 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID#: BBBW71 LATITUDE: 55° 5.8' N ( 55.09597) LONGITUDE: 131° 13.3' W (-131.22211) The primary bench mark is set flush in bedrock 43.2 m (142 ft) SSE from the highpoint of the prominent rock islet, 11 m (36.1 ft) seaward of the island s wood line, 1 m (3.28 ft) above and 5 m (16.4 ft) inshore of MHW line, and 0.5 m (1.6 ft) above the black stain on the nearby rocks.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9450296 PUBLICATION DATE: 07/14/2010 Name: CUSTOM HOUSE COVE, MARY ISLAND AK NOAA Chart: 17424 Latitude: 55° 6.0' N ( 55.10000) USGS Quad: KETCHIKAN A-4 Longitude: 131° 13.0' W (-131.21700) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 0296 B 2010 DESIGNATION: 945 0296 B MONUMENTATION: Tidal Station disk VM#: 19628 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 55° 5.7' N ( 55.09567) LONGITUDE: 131° 13.3' W (-131.22186) The bench mark is set flush in bedrock 67 m (220 ft) SSE from the highpoint of the prominent rock islet, 23 m (75 ft) south of bench mark 945 0296 A, 4 m (13.1ft) seaward of woodline, and 3 m (9.8 ft) above and 11 m ( 36.1 ft) inshore of MHW line. BENCH MARK STAMPING: 0296 C 2010 DESIGNATION: 945 0296 C MONUMENTATION: Tidal Station disk VM#: 19629 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 55° 5.7' N ( 55.09536) LONGITUDE: 131° 13.3' W (-131.22178) The bench mark is set flush in a bedrock finger outcrop extending 6 m (19.7 ft) seaward of tree line, 107 m (351 ft) SSE from highpoint of nearby rock islet, 72 m (237 ft) south from bench mark 945 0296 A, 42 m (138 ft) south from bench mark 945 0296 B, 5 m (16.4 ft) seaward of tree line, 2 m (6.6 ft) above and 5 m (16.4 ft) inshore of MHW line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9450296 PUBLICATION DATE: 07/14/2010 Name: CUSTOM HOUSE COVE, MARY ISLAND AK NOAA Chart: 17424 Latitude: 55° 6.0' N ( 55.10000) USGS Quad: KETCHIKAN A-4 Longitude: 131° 13.0' W (-131.21700) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 0296 D 2010 DESIGNATION: 945 0296 D MONUMENTATION: Tidal Station disk VM#: 19630 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 55° 5.7' N ( 55.09494) LONGITUDE: 131° 13.3' W (-131.22225) The bench mark is set flush in a boulder 140 m (459 ft) south from high point of rock islet, 121 m (396 ft) SSW from bench mark 945 0296 A, 88 m (288 ft) SSW from bench mark 945 0296 B, 4 m (13.1 ft) seaward of a 1 m (3.3 ft) rocky ledge in tree line, and 2 m (6.6 ft) above and 8 m (26.2 ft) inshore of MHW line. BENCH MARK STAMPING: 0296 E 2010 DESIGNATION: 945 0296 E MONUMENTATION: Tidal Station disk VM#: 19631 AGENCY: National Ocean Service (NOS) IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID: LATITUDE: 55° 5.7' N ( 55.09472) LONGITUDE: 131° 13.4' W (-131.22253) The bench mark is set flush in bedrock 113 m (372 ft) SSW from bench mark 945 0296 A, 82 m (270 ft) SSW from bench mark 945 0296 C, 2 m (6.6 ft) seaward of the tree line, and 3 m (9.8 ft) above and 10 m (32.8 ft) inshore of MHW line.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9450296 PUBLICATION DATE: 07/14/2010 Name: CUSTOM HOUSE COVE, MARY ISLAND AK NOAA Chart: 17424 Latitude: 55° 6.0' N ( 55.10000) USGS Quad: KETCHIKAN A-4 Longitude: 131° 13.0' W (-131.21700) T I D A L D A T U M S Tidal datums at CUSTOM HOUSE COVE, MARY ISLAND based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: April 2010 - May 2010 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 = 4.646 MEAN HIGH WATER MHW = 4.370 MEAN SEA LEVEL MSL = 2.428 MEAN TIDE LEVEL MTL = 2.422 MEAN LOW WATER MLW = 0.474 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 0296 A 2010 5.604 1.235 0296 B 2010 5.148 0.778 0296 C 2010 5.343 0.973 0296 D 2010 5.670 1.300 0296 E 2010 5.702 1.332
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9450296 PUBLICATION DATE: 07/14/2010 Name: CUSTOM HOUSE COVE, MARY ISLAND AK NOAA Chart: 17424 Latitude: 55° 6.0' N ( 55.10000) USGS Quad: KETCHIKAN A-4 Longitude: 131° 13.0' W (-131.21700) 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.