U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 Station ID: 8723812 PUBLICATION DATE: 11/18/2005 Name: SHELL KEY CHANNEL FL NOAA Chart: 11449 Latitude: 24° 54.8' N ( 24.91330) USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 39.6' W ( -80.66000) To reach the tidal bench marks from the Teatable Key Channel bridge, proceed NE for 1.6 km (1.0 statute mi) to a 91 m x 12 m (300 ft x 40 ft) key on the east side of Shell Key Channel. The bench marks are located along the north shortline of the Key. The tide gage and staff were located offshore 46 m (150 ft) NW of the NW shoreline. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 1 1975 DESIGNATION: 872 3812 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 10965 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 24° 54.8' N ( 24.91330) LONGITUDE: 80° 39.6' W ( -80.66000) The primary bench mark is a disk set flush in concrete atop a copper-clad rod near the west end of the Key, 15.45 m (50.7 ft) SSW of bench mark NO 2 1975, 11 m (35 ft) NE of the westernmost part of the Key, 0.24 m (0.8 ft) NW of a witness post, and 0.12 m (0.4 ft) above ground level. BENCH MARK STAMPING: NO 2 1975 DESIGNATION: 872 3812 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 10966 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 24° 54.8' N ( 24.91330) LONGITUDE: 80° 39.6' W ( -80.66000) The bench mark is a disk set flush in concrete atop a copper-clad rod, 38 m (125 ft) WSW of bench mark NO 3 1975, 6 m (20 ft) NW of the SE shoreline, 0.24 m (0.8 ft) WSW of a witness post, and 0.09 m (0.3 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 Station ID: 8723812 PUBLICATION DATE: 11/18/2005 Name: SHELL KEY CHANNEL FL NOAA Chart: 11449 Latitude: 24° 54.8' N ( 24.91330) USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 39.6' W ( -80.66000) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 3 1975 DESIGNATION: 872 3812 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 10967 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 24° 54.8' N ( 24.91330) LONGITUDE: 80° 39.6' W ( -80.66000) The bench mark is a disk set flush in concrete atop a copper-clad rod, 18.59 m (6.0 ft) WSW of bench mark NO 4 1975, 5 m (15 m) SE of the NW shoreline, 0.27 m (0.9 ft) west of a witness post, and 0.15 m (0.5 ft) above ground level. BENCH MARK STAMPING: NO 4 1975 DESIGNATION: 872 3812 TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 10968 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 24° 54.8' N ( 24.91330) LONGITUDE: 80° 39.6' W ( -80.66000) The bench mark is a disk set flush in concrete atop a copper-clad rod, located on the NE tip of the Key, 5 m (15 ft) SE of the NW shoreline, 0.34 m (1.1 ft) WSW of a witness post, and 0.06 m (0.2 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 Station ID: 8723812 PUBLICATION DATE: 11/18/2005 Name: SHELL KEY CHANNEL FL NOAA Chart: 11449 Latitude: 24° 54.8' N ( 24.91330) USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 39.6' W ( -80.66000) T I D A L D A T U M S Tidal datums at SHELL KEY CHANNEL based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: June 1975 - June 1975 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8724580 KEY WEST Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 0.352 MEAN HIGH WATER MHW = 0.322 MEAN SEA LEVEL MSL = 0.177 MEAN TIDE LEVEL MTL = 0.169 MEAN LOW WATER MLW = 0.016 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW NO 1 1975 0.540 0.218 NO 2 1975 0.525 0.203 NO 3 1975 0.602 0.280 NO 4 1975 0.622 0.300
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 Station ID: 8723812 PUBLICATION DATE: 11/18/2005 Name: SHELL KEY CHANNEL FL NOAA Chart: 11449 Latitude: 24° 54.8' N ( 24.91330) USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 39.6' W ( -80.66000) 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.