U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 Station ID: 8723999 PUBLICATION DATE: 05/12/2004 Name: SOMBRERO KEY LIGHTHOUSE FL NOAA Chart: 11449 Latitude: 24° 37.6' N ( 24.62670) USGS Quad: MARATHON Longitude: 81° 6.7' W ( -81.11170) To reach the tidal bench marks from the east end of Seven Mile Bridge at Knight Key, proceed SSE for 9.0 km (5.6 statute mi) to Sombrero Key Lighthouse. The lighthouse is an octagonal steel skeleton tower on pile foundation. The bench marks are located on the lighthouse structure. The tide gage and staff were also located on the lighthouse structure just east of the landing platform. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 1 DESIGNATION: 872 3999 TIDAL 1 MONUMENTATION: Bolt VM#: 6300 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Lighthouse structure OPUS PID: LATITUDE: 24° 37.6' N ( 24.62670) LONGITUDE: 81° 6.7' W ( -81.11170) The primary bench mark is the high point of the northern nut on the westernmost stud at the first leg joint clockwise from the landing platform, 8.63 m (28.3 ft) ENE of bench mark NO 4 X, and 0.3 m (1 ft) above the landing platform. BENCH MARK STAMPING: NO 2 DESIGNATION: 872 3999 TIDAL 2 MONUMENTATION: Bolt VM#: 6301 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Lighthouse structure OPUS PID: LATITUDE: 24° 37.6' N ( 24.62670) LONGITUDE: 81° 6.7' W ( -81.11170) The bench mark is the high point of the eastern nut on the SW stud at the first leg joint counter-clockwise from the landing platform, 8.38 m (27.5 ft) north of bench mark NO 4 X, 6.49 m (21.3 ft) west of bench mark NO 1, and 0.3 m (1 ft) above the landing platform.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 Station ID: 8723999 PUBLICATION DATE: 05/12/2004 Name: SOMBRERO KEY LIGHTHOUSE FL NOAA Chart: 11449 Latitude: 24° 37.6' N ( 24.62670) USGS Quad: MARATHON Longitude: 81° 6.7' W ( -81.11170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 3 DESIGNATION: 872 3999 TIDAL 3 MONUMENTATION: Bolt VM#: 6302 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Lighthouse structure OPUS PID: LATITUDE: 24° 37.6' N ( 24.62670) LONGITUDE: 81° 6.7' W ( -81.11170) The bench mark is the high point of the western nut on the NE stud at the second leg joint counter-clockwise from the landing platform, 5.94 m (19.5 ft) west of bench mark NO 2, and 0.3 m (1 ft) above the landing platform. BENCH MARK STAMPING: NO 4X DESIGNATION: 872 3999 TIDAL 4X MONUMENTATION: Bolt VM#: 6303 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Lighthouse structure OPUS PID: LATITUDE: 24° 37.6' N ( 24.62670) LONGITUDE: 81° 6.7' W ( -81.11170) The bench mark is the north end head of the most easterly pin at the center leg joint, 8.26 m (27.1 ft) SE of bench mark NO 3, and 6 cm (0.2 ft) above the landing platform.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 Station ID: 8723999 PUBLICATION DATE: 05/12/2004 Name: SOMBRERO KEY LIGHTHOUSE FL NOAA Chart: 11449 Latitude: 24° 37.6' N ( 24.62670) USGS Quad: MARATHON Longitude: 81° 6.7' W ( -81.11170) T I D A L D A T U M S Tidal datums at SOMBRERO KEY LIGHTHOUSE based on: LENGTH OF SERIES: 8 MONTHS TIME PERIOD: April 1971 - November 1971 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8723747 TAVERNIER HAWK CHANNEL Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 0.625 MEAN HIGH WATER MHW = 0.549 MEAN SEA LEVEL MSL = 0.308 MEAN TIDE LEVEL MTL = 0.305 MEAN LOW WATER MLW = 0.060 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 5.029 4.480 NO 2 5.057 4.508 NO 3 5.060 4.511 NO 4X 4.830 4.281 Foot Notes: Bench mark NO 4X is based on one differential leveling connection and does not meet the quality control standards of the NOS. Therefore, caution should be used when deriving elevations for this mark.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 Station ID: 8723999 PUBLICATION DATE: 05/12/2004 Name: SOMBRERO KEY LIGHTHOUSE FL NOAA Chart: 11449 Latitude: 24° 37.6' N ( 24.62670) USGS Quad: MARATHON Longitude: 81° 6.7' W ( -81.11170) 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.