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Datums Page Page 1 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
To reach the tidal bench marks by boat from the west end of Seven Mile Bridge on
Little Duck Key, proceed NNW 10.1 km (6.3 statute mi) to the SW end of West
Bahia Honda Key. The bench marks are located on the SW end of the Key, just
north of the south end. The tide gage and staff were located on the Government
Wildlife Refuge pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: DOCK 1935
DESIGNATION: DOCK 1935
MONUMENTATION: Triangulation Station disk VM#: 6361
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA1565
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 46.8' N ( 24.78000) LONGITUDE: 81° 16.2' W ( -81.27000)
The primary bench mark is a disk set in a concrete monument located on the south
point of the Key, 79 m (260 ft) north of the south end of the Key, and 20 m (66
ft) south of the old pier on the west shore, and 0.15 m (0.5 ft) east of a
witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 1936
DESIGNATION: 872 4129 NO 1936
ALIAS: NO 19
MONUMENTATION: Tidal Station disk VM#: 6360
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete block OPUS PID:
LATITUDE: 24° 46.8' N ( 24.78000) LONGITUDE: 81° 16.3' W ( -81.27170)
The bench mark is a disk set in a round concrete block, 67 m (220 ft) north of
the south end of the Key, 15.70 m (51.5 ft) SW of bench mark DOCK 2 1935, 12.19
m (40.0 ft) SE of Dock 1935, and 0.06 m (0.2 ft) above ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: DOCK NO 1 1935
DESIGNATION: DOCK RM 1
MONUMENTATION: Reference Mark disk VM#: 6362
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 46.8' N ( 24.78000) LONGITUDE: 81° 16.3' W ( -81.27170)
The bench mark is a disk set in a concrete monument, 11.03 m (36.2 ft) NNW of
triangulation station DOCK 1935, and 0.21 m (0.7 ft) west of a witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: DOCK NO 2 1935
DESIGNATION: DOCK RM 2
MONUMENTATION: Reference Mark disk VM#: 6363
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 46.8' N ( 24.78000) LONGITUDE: 81° 16.3' W ( -81.27170)
The bench mark is a disk set in a concrete monument, 14.69 m (48.2 ft) ESE of
reference mark NO 1 1935, 11.06 m (36.3 ft) NE of bench mark DOCK 1935, 0.3 m (1
ft) WSW of a witness post, and 0.1 m (0.3 ft) below ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: DOUG 1974
DESIGNATION: DOUG
MONUMENTATION: Tidal Station disk VM#: 6364
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 46.8' N ( 24.78000) LONGITUDE: 81° 16.3' W ( -81.27170)
The bench mark is a disk located 32.22 m (105.7 ft) NW of reference mark DOCK NO
2 1935, 21 m (68 ft) NNW of reference mark DOCK NO 1 1935, and 0.21 m (0.7 ft)
south of a witness post. The bench mark is crimped to the top of a copper-clad
steel rod driven an unspecified depth to refusal, and encased in a PVC pipe and
concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
T I D A L D A T U M S
Tidal datums at WEST BAHIA HONDA KEY based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: June 1974 - June 1974
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 = 0.518
MEAN HIGH WATER MHW = 0.453
MEAN TIDE LEVEL MTL = 0.264
MEAN SEA LEVEL MSL = 0.237
MEAN LOW WATER MLW = 0.075
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
DOCK 1935 0.605 0.152
NO 1936 0.636 0.183
DOCK NO 1 1935 0.660 0.207
DOCK NO 2 1935 0.543 0.090
DOUG 1974 0.805 0.352
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8724129 PUBLICATION DATE: 05/12/2004
Name: WEST BAHIA HONDA KEY
FL
NOAA Chart: 11442 Latitude: 24° 46.8' N ( 24.78000)
USGS Quad: HORSESHOE KEYS Longitude: 81° 16.3' W ( -81.27170)
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.