U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 07/29/1986
Station ID: 8723571 SUPERCEDED DATE: 04/21/2003
Name: MAIN KEY, BARNES SOUND
FLORIDA
NOAA Chart: 11463 Latitude: 25° 14.4' N
USGS Quad: BLACK WATER SOUND Longitude: 80° 24.0' W
To reach the tidal bench marks from U.S. Highway 1 and Point Laura Campgrounds
and Marina, proceed by boat NE for approximately 2.1 statute miles (3.4 km) to
the middle of the eastern shore of Main Key. The bench marks are located along
the eastern shoreline. The tide gage and staff were located offshore 150 feet
(46 m) from the middle of the eastern shoreline of the key.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1975
MONUMENTATION: Survey Disk VM#: 5915
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 75 feet (23 m) west of the shoreline and 62.5 feet (19.0 m)
north of Bench Mark NO 4 1975. The bench mark is 0.2 foot (0.1 m) above the
concrete kickblock and 0.1 foot (0.03 m) above the pipe, crimped to a
copper-clad steel rod driven an unspecified depth to refusal, and encased in a
4-inch PVC pipe and concrete kickblock.
BENCH MARK STAMPING: NO 2 1975
MONUMENTATION: Survey Disk VM#: 5916
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 70.8 feet (21.6 m) WNW of Bench Mark NO 1 1975, and 0.8 foot
(0.2 m) SSE of a witness post. The bench mark is 0.7 foot (0.2 m) above the
concrete kickblock and 0.2 foot (0.1 m) above the pipe, crimped to a copper-clad
steel rod driven an unspecified depth to refusal, and encased in a 4-inch PVC
pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 07/29/1986
Station ID: 8723571 SUPERCEDED DATE: 04/21/2003
Name: MAIN KEY, BARNES SOUND
FLORIDA
NOAA Chart: 11463 Latitude: 25° 14.4' N
USGS Quad: BLACK WATER SOUND Longitude: 80° 24.0' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 3 1975
MONUMENTATION: Survey Disk VM#: 5917
AGENCY: PID:
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 64.0 feet (19.6 m) SSW of Bench Mark NO 2 1975, 63.8 feet
(19.4 m) west of Bench Mark NO 1 1975, and 0.8 foot (0.2 m) NE of a witness
post. The bench mark is 0.4 foot (0.1 m) above ground level, crimped to a
copper-clad steel rod driven an unspecified depth to refusal, and encased in a
4-inch PVC pipe and concrete kickblock.
BENCH MARK STAMPING: NO 4 1975
MONUMENTATION: Survey Disk VM#: 5918
AGENCY: PID:
SETTING CLASSIFICATION: Concrete/Rod Monument
The bench mark is set in concrete atop a copper-clad steel rod driven to
refusal, in a stand of large mangrove and buttonwood trees, 62.5 feet (19.0 m)
south of Bench Mark NO 1 1975, 0.8 foot (0.2 m) north of a witness post, and 0.2
foot (0.1 m) above ground level.
BENCH MARK STAMPING: NO 5 1975
MONUMENTATION: Survey Disk VM#: 5919
AGENCY: PID:
SETTING CLASSIFICATION: Concrete/Rod Monument
The bench mark is set in concrete atop a copper-clad steel rod driven to
refusal, 56 feet (17 m) east of the water line and a sharp curve in the
shoreline, 53.5 feet (16.3 m) east of Bench Mark NO 4 1975, 1.0 foot (0.3 m) SW
of a witness post, and 0.1 foot (0.03 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 07/29/1986
Station ID: 8723571 SUPERCEDED DATE: 04/21/2003
Name: MAIN KEY, BARNES SOUND
FLORIDA
NOAA Chart: 11463 Latitude: 25° 14.4' N
USGS Quad: BLACK WATER SOUND Longitude: 80° 24.0' W
T I D A L D A T U M S
Tidal datums at MAIN KEY, BARNES SOUND based on:
LENGTH OF SERIES: 54 HIGH AND LOW WATE
TIME PERIOD: JULY 24-AUGUST 20, 1975
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8723852 LOWER MATECUMBE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (08/26/1975) = 1.01
MEAN HIGHER HIGH WATER MHHW = 0.48
MEAN HIGH WATER MHW = 0.46
MEAN TIDE LEVEL MTL = 0.26
MEAN LOW WATER MLW = 0.05
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (08/05/1975) = -0.23
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 1 1975 1.06 0.60
NO 2 1975 2.29 1.83
NO 3 1975 1.31 0.85
NO 4 1975 1.81 1.35
NO 5 1975 3.66 3.20
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 07/29/1986
Station ID: 8723571 SUPERCEDED DATE: 04/21/2003
Name: MAIN KEY, BARNES SOUND
FLORIDA
NOAA Chart: 11463 Latitude: 25° 14.4' N
USGS Quad: BLACK WATER SOUND Longitude: 80° 24.0' 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.