U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8724307 PUBLICATION DATE: 05/12/2004
Name: CONTENT KEY,GULF OF MEXICO
FLORIDA
NOAA Chart: 11448 Latitude: 24° 47.4' N
USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W
To reach the tidal bench marks from the west end of the U.S. Highway 1 bridge
over Niles Channel on the east side of Summerland Key, proceed by boat north and
then NW on Niles Channel for 8.9 km (5.5 mi) to Channel Marker #64, then head
north across the shallows for 7.2 km (4.5 mi) to the NE tip of the easternmost
key on the west side of Content Passage. The bench marks are located on the NE
tip of the key. The tide gage and staff were located on a platform offshore.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 2 1970
DESIGNATION: 872 4307 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 11328
AGENCY: National Geodetic Survey (NGS) PID#: AA0338
SETTING CLASSIFICATION: Shallow-set pipe
The primary bench mark is a disk set in a small clearing near the east shoreline
of the key, 5 m (16 ft) west of the east shoreline, and 0.27 m (0.9 ft) NE of a
witness post. The bench mark is set 0.37 m (1.2 ft) above ground level, on top
of a 3-inch pipe driven 3 m (10 ft) to refusal.
BENCH MARK STAMPING: NO 3 1970
DESIGNATION: 872 4307 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 11329
AGENCY: National Geodetic Survey (NGS) PID#: AA0339
SETTING CLASSIFICATION: Shallow-set pipe
The bench mark is a disk set in a small clearing near the east shoreline of the
key, 19.66 m (64.5 ft) NNW of bench mark NO 1A 1973, 15.24 m (50.0 ft) west of
the east shoreline, 11.98 m (39.3 ft) WNW of bench mark NO 2 1970, and 0.24 m
(0.8 ft) ENE of a witness post. The bench mark is set 0.18 m (0.6 ft) above
ground level, on top of a 3-inch pipe driven 3 m (10 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8724307 PUBLICATION DATE: 05/12/2004
Name: CONTENT KEY,GULF OF MEXICO
FLORIDA
NOAA Chart: 11448 Latitude: 24° 47.4' N
USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1970
DESIGNATION: 872 4307 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 11330
AGENCY: National Geodetic Survey (NGS) PID#: AA0341
SETTING CLASSIFICATION: Shallow-set pipe
The bench mark is a disk set in a small clearing near the east shoreline of the
key, 10.12 m (33.2 ft) NE of bench mark NO 4A 1973, 2 m (8 ft) west of the
shoreline, and 0.3 m (1 ft) NE of a witness post. The bench mark is set 0.98 m
(3.2 ft) above ground level, on top of a 3-inch pipe driven 3 m (10 ft) to
refusal.
BENCH MARK STAMPING: NO 1A 1973
DESIGNATION: 872 4307 TIDAL 1 A
MONUMENTATION: Tidal Station disk VM#: 11331
AGENCY: National Ocean Survey (NOS) PID#: AA1632
SETTING CLASSIFICATION: Shallow-set pipe
The bench mark is a disk set in concrete inside a 4-inch metal pipe, in a small
clearing near the east shoreline of the key, 15.06 m (49.4 ft) SSW of bench mark
NO 2 1970, 6 m (20 ft) west of the shoreline, 0.21 m (0.7 ft) east of a witness
post, and 0.06 m (0.2 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8724307 PUBLICATION DATE: 05/12/2004
Name: CONTENT KEY,GULF OF MEXICO
FLORIDA
NOAA Chart: 11448 Latitude: 24° 47.4' N
USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 4A 1973
DESIGNATION: 872 4307 TIDAL 4 A
MONUMENTATION: Tidal Station disk VM#: 11332
AGENCY: National Ocean Survey (NOS) PID#: AA1631
SETTING CLASSIFICATION: Shallow-set pipe
The bench mark is a disk set in a small clearing on the east shoreline of the
key, 19.05 m (62.5 ft) NNW of bench mark NO 2 1970, 11 m (36 ft) north of bench
mark NO 3 1970, 9 m (28 ft) SW of the shoreline, and 0.55 m (1.8 ft) NE of a
witness post. The bench mark is set 0.3 m (1 ft) above ground level, set in
concrete on top of a 3-inch pipe driven 3 m (10 ft) to refusal.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8724307 PUBLICATION DATE: 05/12/2004
Name: CONTENT KEY,GULF OF MEXICO
FLORIDA
NOAA Chart: 11448 Latitude: 24° 47.4' N
USGS Quad: CONTENT KEYS Longitude: 81° 29.0' W
T I D A L D A T U M S
Tidal datums at CONTENT KEY,GULF OF MEXICO based on:
LENGTH OF SERIES: 1 YEAR
TIME PERIOD: March 1974 - February 1975
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8724580 KEY WEST
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (11/04/1971) = 1.408
MEAN HIGHER HIGH WATER (MHHW) = 1.059
MEAN HIGH WATER (MHW) = 0.986
NORTH AMERICAN VERTICAL DATUM-1988 (NAVD) = 0.850
MEAN SEA LEVEL (MSL) = 0.564
MEAN TIDE LEVEL (MTL) = 0.560
MEAN LOW WATER (MLW) = 0.135
MEAN LOWER LOW WATER (MLLW) = 0.000
LOWEST OBSERVED WATER LEVEL (02/05/1974) = -0.338
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 2 1970 1.762 0.776
NO 3 1970 1.702 0.716
NO 5 1970 1.855 0.869
NO 1A 1973 1.384 0.398
NO 4A 1973 1.837 0.851
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8724307 PUBLICATION DATE: 05/12/2004
Name: CONTENT KEY,GULF OF MEXICO
FLORIDA
NOAA Chart: 11448 Latitude: 24° 47.4' N
USGS Quad: CONTENT KEYS Longitude: 81° 29.0' 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.