U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
To reach the tidal bench marks from the post office at Layton proceed 11.3 km
(7.0 mi) SW on U.S. Highway 1 to the junction of a paved road to Indies Resort
and Duck Key, continue 1.6 km (1.0 mi) south and west on the paved road to an
arched bridge over a canal, then 0.08 km (0.05 mi) across the bridge to the
intersection of Corsair Road and West Seaview Drive, proceed 0.8 km (0.5 mi)
south on West Seaview Drive to Schooner Lane, then 0.08 km (0.05 mi) south on
Schooner Lane to the residence of Mr. E. G. Fiske. The bench marks are in the
vicinity of the two residences at the end of Schooner Lane. The tide gage and
staff were located on the canal bulkhead on the property of Dr. Crawford Adams,
on the south side of Duck Key.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: A 329 1970
DESIGNATION: A 329
MONUMENTATION: Bench Mark disk VM#: 6275
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0366
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 46.0' N ( 24.76670) LONGITUDE: 80° 54.7' W ( -80.91170)
The primary bench mark is a disk set in the top of a concrete post on the Fiske
property, 22.19 m (72.8 ft) west of bench mark Z 328 1970, 16.06 m (52.7 ft)
north of the NW corner of the Fiske residence, 7.16 m (23.5 ft) east of the
centerline of the north-south street, 4.57 m (15 ft) west of the centerline of
the driveway leading to the residence, 2 m (6 ft) east of the extended
centerline of a black-topped street leading north, and at driveway level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: W 328 1970
DESIGNATION: W 328
MONUMENTATION: Bench Mark disk VM#: 6277
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0369
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 24° 46.0' N ( 24.76670) LONGITUDE: 80° 54.7' W ( -80.91170)
The bench mark is a disk set in the north end of a concrete seawall, near the
Adams residence (last residence to the south on the point), 24.41 m (80.1 ft)
north of the north corner of the house, 0.43 m (1.4 ft) south of the north end
of the seawall, 0.24 m (0.8 ft) east of the west edge of the seawall, and level
with the top of the seawall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: X 328 1970
DESIGNATION: X 328
MONUMENTATION: Bench Mark disk VM#: 6278
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0367
SETTING CLASSIFICATION: Concrete dock OPUS PID:
LATITUDE: 24° 46.0' N ( 24.76670) LONGITUDE: 80° 54.7' W ( -80.91170)
The bench mark is a disk set in the east end of a concrete dock on the Fiske
property, 20.67 m (67.8 ft) south of the SE corner of the house, 19.08 m (62.6
ft) west of bench mark Y 328 1970, and 0.3 m (1 ft) west of the east end of the
dock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: Y 328 1970
DESIGNATION: Y 328
MONUMENTATION: Bench Mark disk VM#: 6279
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0368
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 24° 46.0' N ( 24.76670) LONGITUDE: 80° 54.7' W ( -80.91170)
The bench mark is a disk set in the top of a concrete seawall along the north
edge of the canal, on the Adams property, 22.40 m (73.5 ft) SE of the SE corner
of the Fiske residence, 20.21 m (66.3 ft) SW of the south corner of the Adams
residence, 19.08 m (62.6 ft) east of bench mark X 328 1970, 0.3 m (1 ft) north
of the north edge of the concrete seawall, and flush with the top of the
seawall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: Z 328 1970
DESIGNATION: Z 328
MONUMENTATION: Bench Mark disk VM#: 6280
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0371
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 46.0' N ( 24.76670) LONGITUDE: 80° 54.7' W ( -80.91170)
The bench mark is a disk set in the top of a concrete monument, near the Fiske
residence, 22.19 m (72.8 ft) east of bench mark A 329 1970, 6 m (20 ft) south of
the centerline of the street, 0.76 m (2.5 ft) north of a utility pole, 0.15 m
(0.5 ft) west of the west edge of a concrete curb, and at road level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
T I D A L D A T U M S
Tidal datums at DUCK KEY based on:
LENGTH OF SERIES: 12 MONTHS
TIME PERIOD: January 1971 - December 1971
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 (11/02/1971) = 0.778
North American Vertical Datum NAVD88 = 0.521
MEAN HIGHER HIGH WATER MHHW = 0.507
MEAN HIGH WATER MHW = 0.448
MEAN SEA LEVEL MSL = 0.247
MEAN TIDE LEVEL MTL = 0.244
MEAN LOW WATER MLW = 0.040
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (02/10/1971) = -0.310
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
A 329 1970 1.653 1.205
W 328 1970 1.833 1.385
X 328 1970 1.470 1.022
Y 328 1970 1.697 1.249
Z 328 1970 1.936 1.488
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8723927 PUBLICATION DATE: 04/01/2004
Name: DUCK KEY
FL
NOAA Chart: 11449 Latitude: 24° 45.9' N ( 24.76500)
USGS Quad: GRASSY KEY Longitude: 80° 54.8' W ( -80.91330)
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.