U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8723933 PUBLICATION DATE: 12/12/2003 Name: GRASSY KEY, ATLANTIC SIDE FL NOAA Chart: 11449 Latitude: 24° 45.3' N ( 24.75500) USGS Quad: GRASSY KEY Longitude: 80° 57.5' W ( -80.95830) To reach the tidal bench marks from the post office in Marathon, proceed NE on U.S. Highway 1 for 12.7 km (7.9 mi) to the Rainbow Bend Resort. The bench marks are in the area around the resort. The tide gage and staff were located on the resorts pier. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 4 1975 DESIGNATION: 872 3933 TIDAL 4 MONUMENTATION: Tidal Station disk VM#: 6284 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0861 SETTING CLASSIFICATION: Concrete pad OPUS PID: LATITUDE: 24° 45.3' N ( 24.75500) LONGITUDE: 80° 57.5' W ( -80.95830) The primary bench mark is a disk set in the south corner of a concrete pad, 22.71 m (74.5 ft) SE of the centerline of U.S. Highway 1, 12.98 m (42.6 ft) south of the north corner of a concrete wall at the north property corner, 10 m (33 ft) NE of bench mark NO 3 1975, 6.25 m (20.5 ft) NE of the centerline of the NE entrance drive to the resort, and 0.15 m (0.5 ft) above ground level. BENCH MARK STAMPING: NO 3 1975 DESIGNATION: 872 3933 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 6283 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0862 SETTING CLASSIFICATION: Concrete walkway OPUS PID: LATITUDE: 24° 45.3' N ( 24.75500) LONGITUDE: 80° 57.5' W ( -80.95830) The bench mark is a disk set in a concrete walkway near the NW entrance to the apartment building near the north corner of the property, and 1.52 m (5.0 ft) west of the NW corner of the building.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8723933 PUBLICATION DATE: 12/12/2003 Name: GRASSY KEY, ATLANTIC SIDE FL NOAA Chart: 11449 Latitude: 24° 45.3' N ( 24.75500) USGS Quad: GRASSY KEY Longitude: 80° 57.5' W ( -80.95830) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 5 1975 DESIGNATION: 872 3933 TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 6285 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0863 SETTING CLASSIFICATION: Concrete walkway OPUS PID: LATITUDE: 24° 45.3' N ( 24.75500) LONGITUDE: 80° 57.5' W ( -80.95830) The bench mark is a disk set in the walk near the NE entrance to the apartment building at the west corner of the property, 34.59 m (113.5 ft) west of bench mark NO 4 1975, and 3.51 m (11.5 ft) NW of the north corner of the building. BENCH MARK STAMPING: 3933 F 1982 DESIGNATION: 872 3933 F TIDAL MONUMENTATION: Tidal Station disk VM#: 6286 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0865 SETTING CLASSIFICATION: Concrete step OPUS PID: LATITUDE: 24° 45.3' N ( 24.75500) LONGITUDE: 80° 57.5' W ( -80.95830) The bench mark is a disk set in the steps leading from the beach to the pool, 10.39 m (34.1 ft) SW of the east corner of the pools patio, 3.69 m (12.1 ft) SE of the south corner of the pool, and 3.26 m (10.7 ft) NE of the south corner of the pools patio, and 1 m (2 ft) above ground.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8723933 PUBLICATION DATE: 12/12/2003 Name: GRASSY KEY, ATLANTIC SIDE FL NOAA Chart: 11449 Latitude: 24° 45.3' N ( 24.75500) USGS Quad: GRASSY KEY Longitude: 80° 57.5' W ( -80.95830) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 3933 G 1982 DESIGNATION: 872 3933 G TIDAL MONUMENTATION: Tidal Station disk VM#: 6287 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0864 SETTING CLASSIFICATION: Concrete walkway OPUS PID: LATITUDE: 24° 45.3' N ( 24.75500) LONGITUDE: 80° 57.5' W ( -80.95830) The bench mark is a disk set in a concrete walkway, 13 m (43 ft) NW of a stairway, 2.44 m (8.0 ft) NE of the center of a path between the two-story apartment building, and 1.43 m (4.7 ft) west of the west corner of the northeasternmost two-story apartment building.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8723933 PUBLICATION DATE: 12/12/2003 Name: GRASSY KEY, ATLANTIC SIDE FL NOAA Chart: 11449 Latitude: 24° 45.3' N ( 24.75500) USGS Quad: GRASSY KEY Longitude: 80° 57.5' W ( -80.95830) T I D A L D A T U M S Tidal datums at GRASSY KEY, ATLANTIC SIDE based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: June 1975 - June 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 = 0.628 North American Vertical Datum NAVD88 = 0.598 MEAN HIGH WATER MHW = 0.568 MEAN SEA LEVEL MSL = 0.324 MEAN TIDE LEVEL MTL = 0.311 MEAN LOW WATER MLW = 0.054 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 4 1975 1.816 1.248 NO 3 1975 1.803 1.235 NO 5 1975 1.789 1.221 3933 F 1982 1.936 1.368 3933 G 1982 1.853 1.285 Foot Notes: Bench marks 3933 F 1982 and 3933 G 1982 are based on one differential leveling connection and do not meet the quality control standards of the NOS. Therefore, caution should be used when deriving elevations for these marks.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8723933 PUBLICATION DATE: 12/12/2003 Name: GRASSY KEY, ATLANTIC SIDE FL NOAA Chart: 11449 Latitude: 24° 45.3' N ( 24.75500) USGS Quad: GRASSY KEY Longitude: 80° 57.5' W ( -80.95830) 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.