U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8724307 PUBLICATION DATE: 05/12/2004 Name: CONTENT KEY,GULF OF MEXICO FL NOAA Chart: 11448 Latitude: 24° 47.4' N ( 24.79000) USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W ( -81.48330) To reach the tidal bench marks from the west end of the U.S. Highway 1 bridge over Niles Channel on the east side of Summerland Key, proceed by boat north and then NW on Niles Channel for 8.9 km (5.5 mi) to Channel Marker #64, then head north across the shallows for 7.2 km (4.5 mi) to the NE tip of the easternmost key on the west side of Content Passage. The bench marks are located on the NE tip of the key. The tide gage and staff were located on a platform offshore. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 2 1970 DESIGNATION: 872 4307 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 11328 AGENCY: National Geodetic Survey (NGS) IDB PID#: AA0338 SETTING CLASSIFICATION: Shallow-set pipe OPUS PID: LATITUDE: 24° 47.4' N ( 24.79000) LONGITUDE: 81° 29.0' W ( -81.48330) The primary bench mark is a disk set in a small clearing near the east shoreline of the key, 5 m (16 ft) west of the east shoreline, and 0.27 m (0.9 ft) NE of a witness post. The bench mark is set 0.37 m (1.2 ft) above ground level, on top of a 3-inch pipe driven 3 m (10 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8724307 PUBLICATION DATE: 05/12/2004 Name: CONTENT KEY,GULF OF MEXICO FL NOAA Chart: 11448 Latitude: 24° 47.4' N ( 24.79000) USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W ( -81.48330) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 3 1970 DESIGNATION: 872 4307 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 11329 AGENCY: National Geodetic Survey (NGS) IDB PID#: AA0339 SETTING CLASSIFICATION: Shallow-set pipe OPUS PID: LATITUDE: 24° 47.4' N ( 24.79000) LONGITUDE: 81° 29.0' W ( -81.48330) The bench mark is a disk set in a small clearing near the east shoreline of the key, 19.66 m (64.5 ft) NNW of bench mark NO 1A 1973, 15.24 m (50.0 ft) west of the east shoreline, 11.98 m (39.3 ft) WNW of bench mark NO 2 1970, and 0.24 m (0.8 ft) ENE of a witness post. The bench mark is set 0.18 m (0.6 ft) above ground level, on top of a 3-inch pipe driven 3 m (10 ft) to refusal. BENCH MARK STAMPING: NO 5 1970 DESIGNATION: 872 4307 TIDAL 5 MONUMENTATION: Tidal Station disk VM#: 11330 AGENCY: National Geodetic Survey (NGS) IDB PID#: AA0341 SETTING CLASSIFICATION: Shallow-set pipe OPUS PID: LATITUDE: 24° 47.4' N ( 24.79000) LONGITUDE: 81° 29.0' W ( -81.48330) The bench mark is a disk set in a small clearing near the east shoreline of the key, 10.12 m (33.2 ft) NE of bench mark NO 4A 1973, 2 m (8 ft) west of the shoreline, and 0.3 m (1 ft) NE of a witness post. The bench mark is set 0.98 m (3.2 ft) above ground level, on top of a 3-inch pipe driven 3 m (10 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8724307 PUBLICATION DATE: 05/12/2004 Name: CONTENT KEY,GULF OF MEXICO FL NOAA Chart: 11448 Latitude: 24° 47.4' N ( 24.79000) USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W ( -81.48330) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 1A 1973 DESIGNATION: 872 4307 TIDAL 1 A MONUMENTATION: Tidal Station disk VM#: 11331 AGENCY: National Ocean Survey (NOS) IDB PID#: AA1632 SETTING CLASSIFICATION: Shallow-set pipe OPUS PID: LATITUDE: 24° 47.4' N ( 24.79000) LONGITUDE: 81° 29.0' W ( -81.48330) The bench mark is a disk set in concrete inside a 4-inch metal pipe, in a small clearing near the east shoreline of the key, 15.06 m (49.4 ft) SSW of bench mark NO 2 1970, 6 m (20 ft) west of the shoreline, 0.21 m (0.7 ft) east of a witness post, and 0.06 m (0.2 ft) above ground level. BENCH MARK STAMPING: NO 4A 1973 DESIGNATION: 872 4307 TIDAL 4 A MONUMENTATION: Tidal Station disk VM#: 11332 AGENCY: National Ocean Survey (NOS) IDB PID#: AA1631 SETTING CLASSIFICATION: Shallow-set pipe OPUS PID: LATITUDE: 24° 47.4' N ( 24.79000) LONGITUDE: 81° 29.0' W ( -81.48330) The bench mark is a disk set in a small clearing on the east shoreline of the key, 19.05 m (62.5 ft) NNW of bench mark NO 2 1970, 11 m (36 ft) north of bench mark NO 3 1970, 9 m (28 ft) SW of the shoreline, and 0.55 m (1.8 ft) NE of a witness post. The bench mark is set 0.3 m (1 ft) above ground level, set in concrete on top of a 3-inch pipe driven 3 m (10 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8724307 PUBLICATION DATE: 05/12/2004 Name: CONTENT KEY,GULF OF MEXICO FL NOAA Chart: 11448 Latitude: 24° 47.4' N ( 24.79000) USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W ( -81.48330) T I D A L D A T U M S Tidal datums at CONTENT KEY,GULF OF MEXICO based on: LENGTH OF SERIES: 1 YEAR TIME PERIOD: March 1974 - February 1975 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 (11/04/1971) = 1.408 MEAN HIGHER HIGH WATER MHHW = 1.059 MEAN HIGH WATER MHW = 0.986 North American Vertical Datum NAVD88 = 0.850 MEAN SEA LEVEL MSL = 0.564 MEAN TIDE LEVEL MTL = 0.560 MEAN LOW WATER MLW = 0.135 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (02/05/1974) = -0.338 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW NO 2 1970 1.762 0.776 NO 3 1970 1.702 0.716 NO 5 1970 1.855 0.869 NO 1A 1973 1.384 0.398 NO 4A 1973 1.837 0.851
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8724307 PUBLICATION DATE: 05/12/2004 Name: CONTENT KEY,GULF OF MEXICO FL NOAA Chart: 11448 Latitude: 24° 47.4' N ( 24.79000) USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W ( -81.48330) 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.