U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8724138 PUBLICATION DATE: 05/09/2003 Name: BAHIA HONDA KEY FL NOAA Chart: 11449 Latitude: 24° 39.3' N ( 24.65500) USGS Quad: BIG PINE KEY Longitude: 81° 16.9' W ( -81.28170) To reach the tidal bench marks from the Post Office at Marathon, proceed 21.6 km (13.4 mi) SW on U.S Highway 1 to the east end of the Bahia Honda Bridge over Big Spanish Channel, 0.3 km (0.2 mi) south of the new bridge. The bench marks are located on the old highway bridge which is above an abandoned railroad bridge at the state recreation area, and near the tackle shop. The tide gage and staff were located on the NE concrete wingwall of the railroad bridge. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: W BAHIA RM 2 1935 DESIGNATION: 872 4138 W BAHIA RM 2 MONUMENTATION: Tidal Station disk VM#: 6369 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: AA0269 SETTING CLASSIFICATION: Concrete wing wall OPUS PID: LATITUDE: 24° 39.2' N ( 24.65330) LONGITUDE: 81° 16.9' W ( -81.28170) The primary bench mark is a disk set in the top of the south concrete wingwall of the old bridge, 96 m (315 ft) west of the east end of the bridge, 10 m (33 ft) south of the centerline of the highway, 5.24 m (17.2 ft) SE of bench mark NO 4 1936, and 11 m (35 ft) below highway level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8724138 PUBLICATION DATE: 05/09/2003 Name: BAHIA HONDA KEY FL NOAA Chart: 11449 Latitude: 24° 39.3' N ( 24.65500) USGS Quad: BIG PINE KEY Longitude: 81° 16.9' W ( -81.28170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 4138 F 1982 DESIGNATION: 872 4138 F MONUMENTATION: Tidal Station disk VM#: 6365 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0898 SETTING CLASSIFICATION: Concrete walkway OPUS PID: LATITUDE: 24° 39.3' N ( 24.65500) LONGITUDE: 81° 16.9' W ( -81.28170) The bench mark is a disk set in a concrete walkway, near the tackle shop, 10.79 m (35.4 ft) NW of the south corner of the dive shop, 5.03 m (16.5 ft) east of the NE edge of the parking lot, 1.34 m (4.4 ft) SSW of the west corner of the tackle shop, and 0.15 m (0.5 ft) SW of the stairs behind the tackle shop. BENCH MARK STAMPING: D 70 RESET 1936 TIDAL NO 2 DESIGNATION: 872 4138 D 70 RESET MONUMENTATION: Tidal Station disk VM#: 6366 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: AA0267 SETTING CLASSIFICATION: Concrete wing wall OPUS PID: LATITUDE: 24° 39.3' N ( 24.65500) LONGITUDE: 81° 16.9' W ( -81.28170) The bench mark is a disk set in the top of the north concrete wingwall of the old bridge, 96 m (315 ft) west of the east end of the bridge, 5 m (16 ft) north of the centerline of the highway, and 9 m (30 ft) below highway level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8724138 PUBLICATION DATE: 05/09/2003 Name: BAHIA HONDA KEY FL NOAA Chart: 11449 Latitude: 24° 39.3' N ( 24.65500) USGS Quad: BIG PINE KEY Longitude: 81° 16.9' W ( -81.28170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: G 329 1970 DESIGNATION: 872 4138 G 329 MONUMENTATION: Tidal Station disk VM#: 6367 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0271 SETTING CLASSIFICATION: Concrete wing wall OPUS PID: LATITUDE: 24° 39.3' N ( 24.65500) LONGITUDE: 81° 16.8' W ( -81.28000) The bench mark is a disk set in the top of the NW corner of the 6th concrete step from the bottom of the landing near the old bridge, 46 m (150 ft) north of the north edge of the bridge, 43.31 m (142.1 ft) east of the east face of the concrete wingwall of the railroad bridge and the NE corner of the highway bridge, 18 m (58 ft) south of the shoreline, and 3 m (10 ft) above the apparent high water level. BENCH MARK STAMPING: NO 4 1936 DESIGNATION: 872 4138 TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 6368 AGENCY: US Coast and Geodetic Survey (USC&GS) IDB PID#: AA0268 SETTING CLASSIFICATION: Concrete wing wall OPUS PID: LATITUDE: 24° 39.3' N ( 24.65500) LONGITUDE: 81° 16.9' W ( -81.28170) The bench mark is a disk set in the top of the south concrete wingwall of the old bridge, 96 m (315 ft) west of the east end of the bridge, 5 m (16 ft) south of the centerline of the highway, and 9 m (30 ft) below highway level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8724138 PUBLICATION DATE: 05/09/2003 Name: BAHIA HONDA KEY FL NOAA Chart: 11449 Latitude: 24° 39.3' N ( 24.65500) USGS Quad: BIG PINE KEY Longitude: 81° 16.9' W ( -81.28170) T I D A L D A T U M S Tidal datums at BAHIA HONDA KEY based on: LENGTH OF SERIES: 12 MONTHS TIME PERIOD: February 1971 - January 1972 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8724580 KEY WEST Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (11/05/1971) = 0.772 North American Vertical Datum NAVD88 = 0.512 MEAN HIGHER HIGH WATER MHHW = 0.470 MEAN HIGH WATER MHW = 0.398 MEAN SEA LEVEL MSL = 0.228 MEAN TIDE LEVEL MTL = 0.222 MEAN LOW WATER MLW = 0.046 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (04/26/1971) = -0.298 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW W BAHIA RM 2 1935 6.905 6.507 4138 F 1982 1.671 1.273 D 70 RESET 1936 TIDAL NO 2 7.804 7.406 G 329 1970 3.879 3.481 NO 4 1936 7.861 7.463
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8724138 PUBLICATION DATE: 05/09/2003 Name: BAHIA HONDA KEY FL NOAA Chart: 11449 Latitude: 24° 39.3' N ( 24.65500) USGS Quad: BIG PINE KEY Longitude: 81° 16.9' W ( -81.28170) 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.