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Datums Page Page 1 of 6
Station ID: 8724463 PUBLICATION DATE: 02/05/2004
Name: SNIPE POINT, SNIPE KEYS
FL
NOAA Chart: 11445 Latitude: 24° 41.5' N ( 24.69170)
USGS Quad: SNIPE KEYS Longitude: 81° 40.4' W ( -81.67330)
To reach the tidal bench marks from the bridge between Big Coppitt Key and
Saddlebunch Keys, proceed north by boat for approximately 10.9 km (6.8 statute
mi) to Snipe Point, at the NW extremity of the Snipe Keys group. The bench
marks are located SE of the NW end of the Key. The tide gage and staff were
located SW of the bench marks and offshore of a sand bar.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1973
DESIGNATION: 872 4463 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 11078
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 41.5' N ( 24.69170) LONGITUDE: 81° 40.4' W ( -81.67330)
The primary bench mark is a disk, 198 m (650 ft) SE of the NW extremity of the
key, 30 m (100 ft) NE of the outer edge of the mangroves on the SW side of the
Key, and 14.51 m (47.6 ft) SW of bench mark NO 2 1973. The bench mark is set
flush with the ground, crimped to a copper-clad rod driven 4.9 m (16 ft) to
refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8724463 PUBLICATION DATE: 02/05/2004
Name: SNIPE POINT, SNIPE KEYS
FL
NOAA Chart: 11445 Latitude: 24° 41.5' N ( 24.69170)
USGS Quad: SNIPE KEYS Longitude: 81° 40.4' W ( -81.67330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 2 1973
DESIGNATION: 872 4463 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 11079
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 41.5' N ( 24.69170) LONGITUDE: 81° 40.4' W ( -81.67330)
The bench mark is a disk, 198 m (650 ft) SE of the NW extremity of the key, 37 m
(120 ft) NE of the outer edge of the mangroves, 12.56 m (41.2 ft) WSW of
hydrographic station "NORTH SNIPE HYDRO 1934", and 5.18 m (17.0 ft) ENE of a
multi-trunked wax myrtle. The bench mark is set 6 cm (0.2 ft) below ground
level, crimped to a copper-clad steel rod driven 3.7 m (12 ft) to refusal.
BENCH MARK STAMPING: NO 3 1973
DESIGNATION: 872 4463 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 11080
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 41.5' N ( 24.69170) LONGITUDE: 81° 40.4' W ( -81.67330)
The bench mark is a disk, 213 m (700 ft) SE of the NW extremity of the key, 37 m
(120 ft) NE of the outer edge of the mangroves, 14.54 m (47.7 ft) ESE of bench
mark NO 2 1973, 13.14 m (43.1 ft) SSE of bench mark NORTH SNIPE HYDRO 1934, and
11.28 m (37.0 ft) SE of a multi-trunked wax myrtle . The bench mark is set 6 cm
(0.2 ft) above the ground, crimped to a copper-clad steel rod driven 3.7 m (12
ft) to refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8724463 PUBLICATION DATE: 02/05/2004
Name: SNIPE POINT, SNIPE KEYS
FL
NOAA Chart: 11445 Latitude: 24° 41.5' N ( 24.69170)
USGS Quad: SNIPE KEYS Longitude: 81° 40.4' W ( -81.67330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 4 1973
DESIGNATION: 872 4463 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 11081
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 41.5' N ( 24.69170) LONGITUDE: 81° 40.4' W ( -81.67330)
The bench mark is a disk, 232 m (760 ft) SE of the NW extremity of the key, 46 m
(150 ft) NE of the outer edge of the mangroves, 24.38 m (80.0 ft) SE of bench
mark NO 3 1973. The bench mark is set 6 cm (0.2 ft) above the ground, crimped
to a copper-clad steel rod driven 3.7 m (12 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8724463 PUBLICATION DATE: 02/05/2004
Name: SNIPE POINT, SNIPE KEYS
FL
NOAA Chart: 11445 Latitude: 24° 41.5' N ( 24.69170)
USGS Quad: SNIPE KEYS Longitude: 81° 40.4' W ( -81.67330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NORTH SNIPE HYDRO 1934
DESIGNATION: NORTH SNIPE 1934
MONUMENTATION: Triangulation Station disk VM#: 11082
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA1122
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 41.8' N ( 24.69670) LONGITUDE: 81° 40.4' W ( -81.67330)
The bench mark is a disk set in the top of a concrete monument located on the
northernmost key of the Snipe Key group on a sand ridge, 198 m (650 ft) south of
the NE extremity, 46 m (150 ft) inshore from the edge of the mangrove line, 8 m
(26 ft) NE of a multi-trunked wax myrtle, and 0.21 m (0.7 ft) above the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8724463 PUBLICATION DATE: 02/05/2004
Name: SNIPE POINT, SNIPE KEYS
FL
NOAA Chart: 11445 Latitude: 24° 41.5' N ( 24.69170)
USGS Quad: SNIPE KEYS Longitude: 81° 40.4' W ( -81.67330)
T I D A L D A T U M S
Tidal datums at SNIPE POINT, SNIPE KEYS based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: January 1974 - February 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 = 0.864
MEAN HIGH WATER MHW = 0.783
MEAN TIDE LEVEL MTL = 0.439
MEAN SEA LEVEL MSL = 0.425
MEAN LOW WATER MLW = 0.095
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 1973 1.260 0.477
NO 2 1973 1.294 0.511
NO 3 1973 0.970 0.187
NO 4 1973 1.177 0.394
NORTH SNIPE HYDRO 1934 1.318 0.535
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8724463 PUBLICATION DATE: 02/05/2004
Name: SNIPE POINT, SNIPE KEYS
FL
NOAA Chart: 11445 Latitude: 24° 41.5' N ( 24.69170)
USGS Quad: SNIPE KEYS Longitude: 81° 40.4' W ( -81.67330)
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.