U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 04/15/1987
Station ID: 8724264 SUPERCEDED DATE: 04/21/2003
Name: BIG TORCH KEY, NILES CHANNEL
FLORIDA
NOAA Chart: 11448 Latitude: 24° 42.3' N
USGS Quad: SUMMERLAND KEY Longitude: 81° 26.0' W
To reach the tidal bench marks from Summerland Key Post Office, proceed east on
U.S. Highway 1 for 3.15 miles (5.07 km) to a paved road leading north on Middle
Torch Key, proceed north and west on the paved road for 2.4 miles (3.9 km) to
the junction of a paved road leading to Big Torch Key, proceed west and north on
the paved road for 2.3 miles (3.7 km) to the property of Stanley Hoke. The
bench marks are located around a landfill and the paved road. The tide gage and
staff were located offshore, west of the residence.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1973
MONUMENTATION: Survey Disk VM#: 6870
AGENCY: PID#: AA0720
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument located at the NW corner of
the landfill west of the Hoke residence, 7.7 feet (2.3 m) east of the west edge
of the fill, 7.0 feet (2.1 m) south of the north edge of the fill, and at ground
level.
BENCH MARK STAMPING: NO 2 1973
MONUMENTATION: Survey Disk VM#: 6871
AGENCY: PID#: AA0719
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument located near the west edge of
the landfill west of the residence, 51.0 feet (15.5 m) south of the north edge
of the fill, 44.3 feet (13.5 m) south of Bench Mark NO 1 1973, 11.6 feet (3.5 m)
east of the west edge of the fill, and 0.2 foot (0.1 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 04/15/1987
Station ID: 8724264 SUPERCEDED DATE: 04/21/2003
Name: BIG TORCH KEY, NILES CHANNEL
FLORIDA
NOAA Chart: 11448 Latitude: 24° 42.3' N
USGS Quad: SUMMERLAND KEY Longitude: 81° 26.0' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 4 1973
MONUMENTATION: Survey Disk VM#: 6873
AGENCY: PID#: AA0718
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument located south of the
residence and north of a canal, 176.9 feet (53.9 m) east of the west end of the
landfill, 6.6 feet (2.0 m) north of the canal on the south side of the fill, and
0.2 foot (0.1 m) above ground level.
BENCH MARK STAMPING: NO 5 1973
MONUMENTATION: Survey Disk VM#: 6874
AGENCY: PID#: AA0717
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set flush in a concrete monument located south of the
residence and north of the canal, 296 feet (90 m) east of the west edge of the
landfill, 119.0 feet (36.3 m) east of Bench Mark NO 4 1973, 30.5 feet (9.3 m)
south of the centerline of the Hoke driveway, 6.0 feet (1.8 m) north of the
canal bank, and at ground level.
BENCH MARK STAMPING: 4264 F 1982
MONUMENTATION: Survey Disk VM#: 6875
AGENCY: PID#: AA0716
SETTING CLASSIFICATION: Rock Outcrop
The bench mark is located 0.1 mile (0.2 km) east of the entrance to the Hoke
property, 164.5 feet (50.1 m) WNW of utility pole #MTK5-95-53, 75.3 feet (23.0
m) NE of utility pole #MTK5-95-54, 35.5 feet (10.8 m) north of the centerline of
the paved road, and 3 feet (1 m) below road level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 04/15/1987
Station ID: 8724264 SUPERCEDED DATE: 04/21/2003
Name: BIG TORCH KEY, NILES CHANNEL
FLORIDA
NOAA Chart: 11448 Latitude: 24° 42.3' N
USGS Quad: SUMMERLAND KEY Longitude: 81° 26.0' W
T I D A L D A T U M S
Tidal datums at BIG TORCH KEY, NILES CHANNEL based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: DECEMBER 1973-FEBRUARY 1974
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8724211 BIG PINE KEY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (12/16/1973) = 2.16
MEAN HIGHER HIGH WATER MHHW = 1.20
MEAN HIGH WATER MHW = 0.94
MEAN TIDE LEVEL MTL = 0.56
MEAN LOW WATER MLW = 0.17
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/23/1973) = -0.58
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1973 3.56 2.62
NO 2 1973 3.21 2.27
NO 4 1973 3.13 2.19
NO 5 1973 3.23 2.29
4264 F 1982 2.16 1.22
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 04/15/1987
Station ID: 8724264 SUPERCEDED DATE: 04/21/2003
Name: BIG TORCH KEY, NILES CHANNEL
FLORIDA
NOAA Chart: 11448 Latitude: 24° 42.3' N
USGS Quad: SUMMERLAND KEY Longitude: 81° 26.0' W
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 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.