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National Ocean Service
Datums Page Page 1 of 5
Station ID: 8723807 PUBLICATION DATE: 11/18/2005
Name: SHELL KEY, N.W.SIDE
FL
NOAA Chart: 11449 Latitude: 24° 55.4' N ( 24.92330)
USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 40.3' W ( -80.67170)
To reach the tidal bench marks, proceed approximately 2.7 km (1.7 mi) from
bridge No. 29A. The bench marks are located on the NW side of Shell Key, in a
mud clearing that is approximately 45.72 m x 45.72 m (150.0 ft x 150.0 ft).
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1975
DESIGNATION: 872 3807 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 10801
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper clad steel rod OPUS PID:
LATITUDE: 24° 55.4' N ( 24.92330) LONGITUDE: 80° 40.3' W ( -80.67170)
The primary bench mark is a disk located 166 m (545 ft) NE of bench mark Boutte
1934, 8.23 m (27.0 ft) WNW of the shoreline, on the NW side of the Key, 2.7 km
(1.7 mi) from Bridge No. 29A, and 0.06 m (0.2 ft) above the level of the ground.
The bench mark is set atop a copper rod driven to refusal, set in a concrete
square that projects 0.06 m (0.2 ft) above the ground.
BENCH MARK STAMPING: NO 2 1975
DESIGNATION: 872 3807 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 10802
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper clad steel rod OPUS PID:
LATITUDE: 24° 55.4' N ( 24.92330) LONGITUDE: 80° 40.3' W ( -80.67170)
The bench mark is a disk located 19.39 m (63.6 ft) NE of bench mark NO 1 1975,
10.67 m (35.0 ft) WNW of the shoreline, on the NW side of the Key, 2.7 km (1.7
mi) from Bridge No. 29A, and 0.09 m (0.3 ft) above the level of the ground. The
bench mark is set atop a copper rod driven to refusal, set in a concrete square
that projects 0.09 m (0.3 ft) above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8723807 PUBLICATION DATE: 11/18/2005
Name: SHELL KEY, N.W.SIDE
FL
NOAA Chart: 11449 Latitude: 24° 55.4' N ( 24.92330)
USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 40.3' W ( -80.67170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1975
DESIGNATION: 872 3807 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 10803
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper clad steel rod OPUS PID:
LATITUDE: 24° 55.4' N ( 24.92330) LONGITUDE: 80° 40.3' W ( -80.67170)
The bench mark is a disk located 23.77 m (78.0 ft) NE of bench mark NO 2 1975,
15.85 m (52.0 ft) NW of the shore line, 1.31 m (4.3 ft) NNW of witness post and
19.51 m (64.0 ft) north of a witness sign that is secured to a DNR "No
Trespassing" sign, on the NW side of the Key, 2.7 km (1.7 mi) from Bridge No.
29A, and 0.06 m (0.2 ft) above the level of the ground. The bench mark is set
atop a copper rod driven to refusal, set in a concrete square that projects 0.03
m (0.1 ft) above the ground.
BENCH MARK STAMPING: NO 4 1975
DESIGNATION: 872 3807 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 10804
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper clad steel rod OPUS PID:
LATITUDE: 24° 55.4' N ( 24.92330) LONGITUDE: 80° 40.3' W ( -80.67170)
The bench mark is a disk located 29.87 m (98.0 ft) ESE of bench mark NO 3 1975,
46 m (151 ft) east of bench mark NO 2 1975, 166 m (545 ft) NE of bench mark
Boutte 1934, 8.23 m (27.0 ft) WNW of the shoreline, on the NW side of the Key,
and 2.7 km (1.7 mi) from Bridge No. 29A. The bench mark is set atop a copper
rod driven to refusal, set in a concrete square that projects 0.06 m (0.2 ft)
above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8723807 PUBLICATION DATE: 11/18/2005
Name: SHELL KEY, N.W.SIDE
FL
NOAA Chart: 11449 Latitude: 24° 55.4' N ( 24.92330)
USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 40.3' W ( -80.67170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BOUTTE 1934
DESIGNATION: BOUTTE
MONUMENTATION: Triangulation Station disk VM#: 10805
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA1353
SETTING CLASSIFICATION: Clay tile pipe OPUS PID:
LATITUDE: 24° 55.4' N ( 24.92330) LONGITUDE: 80° 40.2' W ( -80.67000)
The bench mark is a disk set at a tall mangrove edge projecting 0.12 m (0.4 ft)
above the ground, bears 16.46 m (54.0 ft) SW of bench mark NO ! 1975, 0.15 m
(0.5 ft) west of a witness post, on the NW side of the Key, 2.7 km (1.7 mi) from
Bridge No. 29A, and 21.82 m (71.6 ft) SW of the corner of a shack.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8723807 PUBLICATION DATE: 11/18/2005
Name: SHELL KEY, N.W.SIDE
FL
NOAA Chart: 11449 Latitude: 24° 55.4' N ( 24.92330)
USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 40.3' W ( -80.67170)
T I D A L D A T U M S
Tidal datums at SHELL KEY, N.W.SIDE based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: June 1975 - June 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 = 0.222
MEAN HIGH WATER MHW = 0.186
MEAN TIDE LEVEL MTL = 0.095
MEAN SEA LEVEL MSL = 0.093
MEAN LOW WATER MLW = 0.004
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 0.198 0.012
NO 2 1975 0.260 0.074
NO 3 1975 0.173 -0.013
NO 4 1975 0.211 0.025
BOUTTE 1934 0.279 0.093
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8723807 PUBLICATION DATE: 11/18/2005
Name: SHELL KEY, N.W.SIDE
FL
NOAA Chart: 11449 Latitude: 24° 55.4' N ( 24.92330)
USGS Quad: UPPER MATECUMBE KEY Longitude: 80° 40.3' W ( -80.67170)
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.