U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8723971 PUBLICATION DATE: 05/28/2004 Name: BOOT KEY HARBOR FL NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330) USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500) To reach the tidal bench marks from the east end of the Seven Mile bridge, proceed east on U.S. Highway 1 for 2.4 km (1.5 mi) to County Road C931 (20th Stree Ocean), then turn right and proceed south on County Road C931 for 0.3 km (0.2 mi) to the bridge over Boot Key Harbor. The bench marks are located along the bridge. The tide gage and staff were located on the SE end of the bridge. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 1 1975 DESIGNATION: 872 3971 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 6295 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0890 SETTING CLASSIFICATION: Concrete bridge sidewalk OPUS PID: LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500) The primary bench mark is a disk set flush in the NE corner of the concrete bridge sidewalk, 5.12 m (16.8 ft) east of the centerline of County Road C931, 3 m (11 ft) south of the north end of the bridge, and 0.15 m (0.5 ft) above road level. BENCH MARK STAMPING: NO 2 1975 DESIGNATION: 872 3971 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 6296 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0889 SETTING CLASSIFICATION: Concrete pad OPUS PID: LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500) The bench mark is a disk set flush in a concrete pad for a bridge caution light, 26 m (85 ft) NW of bench mark NO 1 1975, 20.73 m (68.0 ft) north of the NW corner of the bridge, and 6 m (20 ft) west of the centerline of County Road C931.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8723971 PUBLICATION DATE: 05/28/2004 Name: BOOT KEY HARBOR FL NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330) USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 3971 C DESIGNATION: 872 3971 C TIDAL FLDT MONUMENTATION: Bench Mark disk VM#: 6297 AGENCY: Florida Department of Transportation (FLDT) IDB PID#: AA0891 SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID: LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500) The bench mark is a disk set flush in the NW corner of the concrete bridge guardrail, 23 m (75 ft) south of bench mark NO 2 1975, 11 m (35 ft) west of bench mark NO 1 1975, 5.64 m (18.5 ft) west of the centerline of County Road C931, 2.44 m (8.0 ft) south of the north end of the guardrail, and 1 m (3 ft) above road level. BENCH MARK STAMPING: 3971 D 1982 DESIGNATION: 872 3971 D TIDAL MONUMENTATION: Tidal Station disk VM#: 6298 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0892 SETTING CLASSIFICATION: Concrete bridge foundation OPUS PID: LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500) The bench mark is a disk set flush in a concrete foundation for the drawbridge, 57.45 m (188.5 ft) south of the NE corner of the bridge, 11.31 m (37.1 ft) east of the NE corner of the bridge tender's building, and 5.55 m (18.2 ft) east of the centerline of County Road C931.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8723971 PUBLICATION DATE: 05/28/2004 Name: BOOT KEY HARBOR FL NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330) USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 3971 E DESIGNATION: 872 3971 E TIDAL FLDT MONUMENTATION: Bench Mark disk VM#: 6299 AGENCY: Florida Department of Transportation (FLDT) IDB PID#: AA0893 SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID: LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500) The bench mark is a disk set flush in the top of the concrete guardrail located at the SE corner of the bridge, 5.33 m (17.5 ft) east of the centerline of County Road C931, 2.41 m (7.9 ft) north of the south end of the guardrail, 0.15 m (0.5 ft) south of the bridge abutment, and 1 m (3 ft) above road level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8723971 PUBLICATION DATE: 05/28/2004 Name: BOOT KEY HARBOR FL NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330) USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500) T I D A L D A T U M S Tidal datums at BOOT KEY HARBOR based on: LENGTH OF SERIES: 2 MONTHS TIME PERIOD: April 1975 - May 1975 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8724580 KEY WEST Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 0.592 North American Vertical Datum NAVD88 = 0.565 MEAN HIGH WATER MHW = 0.522 MEAN SEA LEVEL MSL = 0.293 MEAN TIDE LEVEL MTL = 0.288 MEAN LOW WATER MLW = 0.053 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 1975 8.402 7.880 NO 2 1975 7.417 6.895 3971 C 9.262 8.740 3971 D 1982 10.137 9.615 3971 E 3.980 3.458 Foot Notes: Bench marks 3971 D 1982 and 3971 E 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: 8723971 PUBLICATION DATE: 05/28/2004 Name: BOOT KEY HARBOR FL NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330) USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500) 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.