U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 9449932 PUBLICATION DATE: 04/21/2003 Name: ARMITAGE ISLAND WA NOAA Chart: 18430 Latitude: 48° 32.1' N ( 48.53500) USGS Quad: BLAKELY ISLAND Longitude: 122° 47.8' W (-122.79700) To reach the tidal bench marks which are accessible only by boat, from the nearest boat launch facilities in Anacortes, Washington, proceed through town on the Highway 20 Spur to the light at Sunset Avenue. Go straight on Sunset Avenue to its terminus in Washington Park. From the boat launch, Armitage Island is approximately 8.5 km (5.3 mi) to the NW across Rosario Strait along the southeastern side of Blakely Island. The bench marks are located along the shore on the southwestern side of the Island. The tide gauge is on a private pier on the west side of the Island. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 1 1972 DESIGNATION: 944 9932 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 13728 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 48° 32.1' N ( 48.53500) LONGITUDE: 122° 47.8' W (-122.79700) The primary bench mark is a disk set in a rock ledge, approximately 11 m (36 ft) SE (163 degrees magnetic) from a shore end of a small dock located on the western shore, and approximately 1 m (4 ft) above the apparent high water mark.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 9449932 PUBLICATION DATE: 04/21/2003 Name: ARMITAGE ISLAND WA NOAA Chart: 18430 Latitude: 48° 32.1' N ( 48.53500) USGS Quad: BLAKELY ISLAND Longitude: 122° 47.8' W (-122.79700) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 3 1972 DESIGNATION: 944 9932 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 13729 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 48° 32.1' N ( 48.53500) LONGITUDE: 122° 47.8' W (-122.79700) The bench mark is a disk set in a rock ledge, located approximately 24 m (78 ft) SW (191 degrees magnetic) from bench mark NO 2 1972, and 0.61 m (2.0 ft) above the apparent high tide mark. BENCH MARK STAMPING: NO 2 1972 DESIGNATION: 944 9932 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 13730 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 48° 32.1' N ( 48.53500) LONGITUDE: 122° 47.8' W (-122.79700) The bench mark is a disk set in a rock ledge, located approximately 15 m (48 ft) SE (177 degrees magnetic) from bench mark NO 1 1972, and 1 m (4 ft) above the apparent high tide mark.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 9449932 PUBLICATION DATE: 04/21/2003 Name: ARMITAGE ISLAND WA NOAA Chart: 18430 Latitude: 48° 32.1' N ( 48.53500) USGS Quad: BLAKELY ISLAND Longitude: 122° 47.8' W (-122.79700) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 4 1972 DESIGNATION: 944 9932 TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 13731 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 48° 32.1' N ( 48.53500) LONGITUDE: 122° 47.8' W (-122.79700) The bench mark is a disk set in a rock ledge, located approximately 16 m (53 ft) SW (201 degrees magnetic) from bench mark NO 3 1972, and 0.91 m (3.0 ft) above the apparent high tide mark. BENCH MARK STAMPING: NO 5 1972 DESIGNATION: 944 9932 TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 13732 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Rock ledge OPUS PID: LATITUDE: 48° 32.1' N ( 48.53500) LONGITUDE: 122° 47.8' W (-122.79700) The bench mark is a disk set in a rock ledge, located approximately 20 m (64 ft) SE (177 degrees magnetic) from bench mark NO 4 1972, and 0.91 m (3 ft) above the apparent high tide mark.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 9449932 PUBLICATION DATE: 04/21/2003 Name: ARMITAGE ISLAND WA NOAA Chart: 18430 Latitude: 48° 32.1' N ( 48.53500) USGS Quad: BLAKELY ISLAND Longitude: 122° 47.8' W (-122.79700) T I D A L D A T U M S Tidal datums at ARMITAGE ISLAND based on: LENGTH OF SERIES: 2 Years TIME PERIOD: June 1998 - May 2000 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 9449880 FRIDAY HARBOR, SAN JUAN CHANNEL Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (12/16/1997) = 3.186 MEAN HIGHER HIGH WATER MHHW = 2.391 MEAN HIGH WATER MHW = 2.204 MEAN TIDE LEVEL MTL = 1.456 MEAN SEA LEVEL MSL = 1.422 MEAN LOW WATER MLW = 0.708 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (12/25/1999) = -1.113 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW NO 1 1972 3.836 1.632 NO 3 1972 3.222 1.018 NO 2 1972 3.837 1.633 NO 4 1972 3.555 1.351 NO 5 1972 3.553 1.349
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 9449932 PUBLICATION DATE: 04/21/2003 Name: ARMITAGE ISLAND WA NOAA Chart: 18430 Latitude: 48° 32.1' N ( 48.53500) USGS Quad: BLAKELY ISLAND Longitude: 122° 47.8' W (-122.79700) 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.