U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 6 Station ID: 8724099 PUBLICATION DATE: 01/23/2004 Name: MISSOURI-LITTLE DUCK CHANNEL FL NOAA Chart: 11449 Latitude: 24° 40.8' N ( 24.68000) USGS Quad: SEVENMILE BRIDGE Longitude: 81° 14.1' W ( -81.23500) To reach the tidal bench marks from the Post Office at Marathron, proceed 16.3 km (10.1 mi) SW on U.S. Highway 1 to the east end of the bridge between Missouri Key and Little Duck Key. The bench marks are located on the concrete wing walls and curbs of the old highway bridge (bridge #19), now used as a fishing pier, and the new bridge. The tide gage and staff were located at the east end of the old bridge on the SE wing wall. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: NO 2 1975 DESIGNATION: 872 4099 TIDAL 2 MONUMENTATION: Tidal Station disk VM#: 6343 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0956 SETTING CLASSIFICATION: Concrete wing wall OPUS PID: LATITUDE: 24° 40.8' N ( 24.68000) LONGITUDE: 81° 14.1' W ( -81.23500) The primary bench mark is a disk set flush in the top of the SE concrete wing wall at the east end of the old bridge, 4.57 m (15.0 ft) SE of the centerline of the old bridge, 1.37 m (4.5 ft) SE of the NE abutment, and 1 m (3 ft) below bridge level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 6 Station ID: 8724099 PUBLICATION DATE: 01/23/2004 Name: MISSOURI-LITTLE DUCK CHANNEL FL NOAA Chart: 11449 Latitude: 24° 40.8' N ( 24.68000) USGS Quad: SEVENMILE BRIDGE Longitude: 81° 14.1' W ( -81.23500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: NO 1 1975 DESIGNATION: 872 4099 TIDAL 1 MONUMENTATION: Tidal Station disk VM#: 6342 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete wing wall OPUS PID: LATITUDE: 24° 40.8' N ( 24.68000) LONGITUDE: 81° 14.1' W ( -81.23500) The bench mark is a disk set flush in the top of the SE concrete wingwall located at the east end of the old bridge, 16 m (54 ft) south of bench mark NO 3 1975, 11 m (36 ft) SE of the bridge abutment, and 9.60 m (31.5 ft) south of bench mark NO 2 1975. BENCH MARK STAMPING: NO 3 1975 DESIGNATION: 872 4099 TIDAL 3 MONUMENTATION: Tidal Station disk VM#: 6344 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0957 SETTING CLASSIFICATION: Concrete curb OPUS PID: LATITUDE: 24° 40.8' N ( 24.68000) LONGITUDE: 81° 14.1' W ( -81.23500) The bench mark is a disk set flush in the top of the NE concrete curb of the old bridge at the east end of the old bridge, 5.49 m (18.0 ft) NE of the south end of the concrete wing wall on the NW side of the bridge, 3 m (11 ft) NW of the centerline of the bridge, and 0.15 m (0.5 ft) above bridge level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 6 Station ID: 8724099 PUBLICATION DATE: 01/23/2004 Name: MISSOURI-LITTLE DUCK CHANNEL FL NOAA Chart: 11449 Latitude: 24° 40.8' N ( 24.68000) USGS Quad: SEVENMILE BRIDGE Longitude: 81° 14.1' W ( -81.23500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 4099 D DESIGNATION: 872 4099 D TIDAL FLDT MONUMENTATION: Bench Mark disk VM#: 6345 AGENCY: Florida Department of Transportation (FLDT) IDB PID#: AA0955 SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID: LATITUDE: 24° 40.8' N ( 24.68000) LONGITUDE: 81° 14.1' W ( -81.23500) The bench mark is a disk set in the top of the concrete guardrail at the NE end of the bridge, 7.13 m (23.4 ft) NW of the centerline of the highway, 3.20 m (10.5 ft) SW of the NE end of the guardrail, 0.15 m (0.5 ft) NE of the abutment, and 1 m (3 ft) above highway level. BENCH MARK STAMPING: 4099 E DESIGNATION: 872 4099 E TIDAL FLDT MONUMENTATION: Bench Mark disk VM#: 6346 AGENCY: Florida Department of Transportation (FLDT) IDB PID#: AA0954 SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID: LATITUDE: 24° 40.7' N ( 24.67830) LONGITUDE: 81° 14.2' W ( -81.23670) The bench mark is a disk set in the top of the concrete guardrail at the SW end of the bridge, 7.10 m (23.3 ft) SE of the centerline of the highway, 3.20 m (10.5 ft) NE of the SW end of the guardrail, 0.18 m (0.6 ft) SW of the abutment, and 1 m (3 ft) above highway level.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 6 Station ID: 8724099 PUBLICATION DATE: 01/23/2004 Name: MISSOURI-LITTLE DUCK CHANNEL FL NOAA Chart: 11449 Latitude: 24° 40.8' N ( 24.68000) USGS Quad: SEVENMILE BRIDGE Longitude: 81° 14.1' W ( -81.23500) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 4099 F 1982 DESIGNATION: 872 4099 F TIDAL MONUMENTATION: Tidal Station disk VM#: 6347 AGENCY: National Ocean Survey (NOS) IDB PID#: AA0953 SETTING CLASSIFICATION: Concrete bridge cheekwall OPUS PID: LATITUDE: 24° 40.7' N ( 24.67830) LONGITUDE: 81° 14.2' W ( -81.23670) The bench mark is a disk set in the concrete bridge cheekwall at the SW end of the bridge, 12.62 m (41.4 ft) SW of a metal guard for an aquaduct, 7.77 m (25.5 ft) NW of the centerline of the highway, and 0.85 m (2.8 ft) SE of the NW edge of the cheekwall.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 6 Station ID: 8724099 PUBLICATION DATE: 01/23/2004 Name: MISSOURI-LITTLE DUCK CHANNEL FL NOAA Chart: 11449 Latitude: 24° 40.8' N ( 24.68000) USGS Quad: SEVENMILE BRIDGE Longitude: 81° 14.1' W ( -81.23500) T I D A L D A T U M S Tidal datums at MISSOURI-LITTLE DUCK CHANNEL based on: LENGTH OF SERIES: 1 MONTH TIME PERIOD: February 1975 - February 1975 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8724138 BAHIA HONDA KEY Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: North American Vertical Datum NAVD88 = 0.421 MEAN HIGHER HIGH WATER MHHW = 0.384 MEAN HIGH WATER MHW = 0.322 MEAN SEA LEVEL MSL = 0.199 MEAN TIDE LEVEL MTL = 0.178 MEAN LOW WATER MLW = 0.034 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 3.120 2.798 NO 1 1975 1.458 1.136 NO 3 1975 3.891 3.569 4099 D 5.500 5.178 4099 E 5.500 5.178 4099 F 1982 4.679 4.357 Foot Notes: Bench marks 4099 D, 4099 E and 4099 F 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 6 of 6 Station ID: 8724099 PUBLICATION DATE: 01/23/2004 Name: MISSOURI-LITTLE DUCK CHANNEL FL NOAA Chart: 11449 Latitude: 24° 40.8' N ( 24.68000) USGS Quad: SEVENMILE BRIDGE Longitude: 81° 14.1' W ( -81.23500) 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.