U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9462676 PUBLICATION DATE: 11/07/2013 Name: BROAD BIGHT AK NOAA Chart: 16531 Latitude: 54° 3.9' N ( 54.06458) USGS Quad: UNIMAK A-6 Longitude: 165° 56.2' W (-165.93706) To reach the tidal bench marks from the Unalaska (Dutch Harbor) City Dock by boat, proceed NNE 14.0 km (7.6 nm) to Priest Rock, then proceed E for 28.2 km (15.2 nm) crossing Akutan Pass past Cape Morgan to the N, then proceed N 1.2 km (0.7 nm) into Broad Bight which is the first beach W of Battery Point on the S end of Akutan Island. The tide gauge is located on the W end of Broad Bight on a rock outcrop 0.3 km (0.2 nm) S of the stream mouth, and the bench marks are on the rock outcrop and boulders along the cliff face to the N. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 2676 A 2013 DESIGNATION: 946 2676 A MONUMENTATION: Tidal Station disk VM#: 20818 AGENCY: National Ocean Service IDB PID#: SETTING CLASSIFICATION: Bedrock OPUS PID#: BBDC14 LATITUDE: 54° 3.9' N ( 54.06447) LONGITUDE: 165° 56.2' W (-165.93717) The primary bench mark is a disk set in the seaward high point of a bedrock outcrop below a rock bluff and S of the stream at the W end of Broad Bight, 31.93 m (104.8 ft) S of the high point of the N most extent of this rock ledge, 16.66 m (54.7 ft) SSE of the grass above the sandy hollow below the rock bluff, and 14.37 m (47.1 ft) SE of the rock bluff nearest the bench mark.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9462676 PUBLICATION DATE: 11/07/2013 Name: BROAD BIGHT AK NOAA Chart: 16531 Latitude: 54° 3.9' N ( 54.06458) USGS Quad: UNIMAK A-6 Longitude: 165° 56.2' W (-165.93706) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 2676 B 2013 DESIGNATION: 946 2676 B MONUMENTATION: Tidal Station disk VM#: 20819 AGENCY: National Ocean Service IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 54° 3.9' N ( 54.06503) LONGITUDE: 165° 56.2' W (-165.93725) The bench mark is a disk set in a boulder 2.00 m (6.5 ft) wide and 0.30 m (1.0 ft) high embedded in black sand inside of a small lagoon S of the mouth of a stream and at the base of a 30 m (100 ft) high rock bluff at the W end of Broad Bight, 31.49 m (130.3 ft) NW of the S edge of the shallow rock lagoon along the rock outcrop, 22.50 m (73.8 ft) SSE of the N end of the rock bluff, 18.20 m (59.7 ft) W of the highest rock outcrop along the edge of the stream at low tide, 1.96 m (6.4 ft) ENE of the rock bluff, and 0.39 m (1.3 ft) above the beach. BENCH MARK STAMPING: 2676 C 2013 DESIGNATION: 946 2676 C MONUMENTATION: Tidal Station disk VM#: 20820 AGENCY: National Ocean Service IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 54° 3.9' N ( 54.06539) LONGITUDE: 165° 56.3' W (-165.93811) The bench mark is a disk set in a 2.00 m (6.5 ft) wide conglomerate boulder W of the stream at the W end of Broad Bight, 83.40 m (273.6 ft) SW of the W bank of the stream near the mouth, 36.60 m (120.1 ft) N of the N end of the rock bluff , 2.85 m (9.35 ft) E of vegetation, and 1.40 m (4.3 ft) above rocky ground covered in kelp.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9462676 PUBLICATION DATE: 11/07/2013 Name: BROAD BIGHT AK NOAA Chart: 16531 Latitude: 54° 3.9' N ( 54.06458) USGS Quad: UNIMAK A-6 Longitude: 165° 56.2' W (-165.93706) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 2676 D 2013 DESIGNATION: 946 2676 D MONUMENTATION: Tidal Station disk VM#: 20821 AGENCY: National Ocean Service IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 54° 4.0' N ( 54.06592) LONGITUDE: 165° 56.3' W (-165.93836) The bench mark is a disk set in a rock at the base of a cliff on black sand amid grass W of the stream at the W end of Broad Bight, 91.10 m (298.9 ft) W of W stream bank, and 7.20 m (23.6 ft) ESE of cliff. BENCH MARK STAMPING: 2676 E 2013 DESIGNATION: 946 2676 E MONUMENTATION: Tidal Station disk VM#: 20822 AGENCY: National Ocean Service IDB PID#: SETTING CLASSIFICATION: Boulder OPUS PID: LATITUDE: 54° 4.0' N ( 54.06647) LONGITUDE: 165° 56.3' W (-165.93806) The bench mark is a disk set in a 4.00 m (13.1 ft) square rock boulder at base of cliff in grass W of the stream at the W end of Broad Bight, 77.0 m (252.6 ft) WNW of W stream bank, 5.30 m (17.4 ft) SE of cliff, and 2.10 m (6.9 ft) above ground.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9462676 PUBLICATION DATE: 11/07/2013 Name: BROAD BIGHT AK NOAA Chart: 16531 Latitude: 54° 3.9' N ( 54.06458) USGS Quad: UNIMAK A-6 Longitude: 165° 56.2' W (-165.93706) T I D A L D A T U M S Tidal datums at BROAD BIGHT based on: LENGTH OF SERIES: 2 MONTHS TIME PERIOD: June 2013 - July 2013 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9459881 KING COVE, DEER PASSAGE, PACIFIC OCEAN Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 1.694 MEAN HIGH WATER MHW = 1.534 MEAN TIDE LEVEL MTL = 0.987 MEAN SEA LEVEL MSL = 0.970 MEAN LOW WATER MLW = 0.439 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 2676 A 2013 6.824 5.290 2676 B 2013 2.524 0.990 2676 C 2013 3.607 2.073 2676 D 2013 4.102 2.568 2676 E 2013 8.976 7.442
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9462676 PUBLICATION DATE: 11/07/2013 Name: BROAD BIGHT AK NOAA Chart: 16531 Latitude: 54° 3.9' N ( 54.06458) USGS Quad: UNIMAK A-6 Longitude: 165° 56.2' W (-165.93706) 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.