U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 4 Station ID: 8723689 PUBLICATION DATE: 05/28/2004 Name: POINT CHARLES, KEY LARGO FL NOAA Chart: 11463 Latitude: 25° 4.9' N ( 25.08170) USGS Quad: ROCK HARBOR Longitude: 80° 26.8' W ( -80.44670) To reach the tidal bench marks from the intersection of Ocean Bay Drive and U.S. Highway 1 (Waldorf Plaza) in Key Largo, proceed south on Ocean Bay Drive for 1.1 km (0.7 mi) over a canal to the intersection of a dirt road. The bench marks are on a small bridge over the canal, at the intersection of Ocean Bay Drive and the dirt road, and along the dirt road. The tide gage and staff were at the south end of the canal. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 2 1975 DESIGNATION: 872 3689 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 5969 AGENCY: National Ocean Survey (NOS) IDB PID#: AC3346 SETTING CLASSIFICATION: Rock outcrop OPUS PID: LATITUDE: 25° 4.9' N ( 25.08170) LONGITUDE: 80° 26.8' W ( -80.44670) The primary bench mark is a disk set in a rock outcrop located at the junction of Ocean Bay Drive and the dirt road, 23 m (75 ft) west of Ocean Bay Drive, and 11 m (35 ft) south of the centerline of the dirt road. BENCH MARK STAMPING: NO 3 1975 DESIGNATION: 872 3689 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 5970 AGENCY: National Ocean Survey (NOS) IDB PID#: AC3347 SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 25° 4.9' N ( 25.08170) LONGITUDE: 80° 26.8' W ( -80.44670) The bench mark is a disk set in the top of a concrete monument along the dirt road, 315 m (1035 ft) west of Ocean Bay Drive, 70 m (230 ft) east of the east edge of the canal, and 4 m (12 ft) south of the centerline of the dirt road.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 4 Station ID: 8723689 PUBLICATION DATE: 05/28/2004 Name: POINT CHARLES, KEY LARGO FL NOAA Chart: 11463 Latitude: 25° 4.9' N ( 25.08170) USGS Quad: ROCK HARBOR Longitude: 80° 26.8' W ( -80.44670) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 3A 1975 DESIGNATION: 872 3689 TIDAL 3 A MONUMENTATION: Tidal Station disk VM#: 5971 AGENCY: National Ocean Survey (NOS) IDB PID#: AC3345 SETTING CLASSIFICATION: Concrete bridge abutment OPUS PID: LATITUDE: 25° 5.0' N ( 25.08330) LONGITUDE: 80° 26.5' W ( -80.44170) The bench mark is a disk set in SE abutment of the Ocean Bay Drive bridge over a small canal, 148 m (485 ft) NNE of bench mark NO 2 1975, and 0.12 m (0.4 ft) above the road.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 4 Station ID: 8723689 PUBLICATION DATE: 05/28/2004 Name: POINT CHARLES, KEY LARGO FL NOAA Chart: 11463 Latitude: 25° 4.9' N ( 25.08170) USGS Quad: ROCK HARBOR Longitude: 80° 26.8' W ( -80.44670) T I D A L D A T U M S Tidal datums at POINT CHARLES, KEY LARGO based on: LENGTH OF SERIES: 3 MONTHS TIME PERIOD: May 1975 - July 1975 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 = 0.722 MEAN HIGH WATER MHW = 0.693 North American Vertical Datum NAVD88 = 0.644 MEAN SEA LEVEL MSL = 0.379 MEAN TIDE LEVEL MTL = 0.374 MEAN LOW WATER MLW = 0.056 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 2 1975 0.945 0.252 NO 3 1975 0.848 0.155 NO 3A 1975 2.571 1.878
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 4 Station ID: 8723689 PUBLICATION DATE: 05/28/2004 Name: POINT CHARLES, KEY LARGO FL NOAA Chart: 11463 Latitude: 25° 4.9' N ( 25.08170) USGS Quad: ROCK HARBOR Longitude: 80° 26.8' W ( -80.44670) 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.