U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 11/06/1984
Station ID: 8725171 SUPERCEDED DATE: 04/21/2003
Name: OUTER CLAM BAY
FLORIDA
NOAA Chart: 11429 Latitude: 26° 12.7' N
USGS Quad: NAPLES NORTH Longitude: 81° 48.8' W
To reach the tidal bench marks from Naples proceed 5.0 miles (8.0 km) north on
U.S. Highway 41 to Seagate Drive, proceed west 0.8 mile (1.3 km) on Seagate
Drive, and continue west to the end of a private dirt road. The bench marks are
located in the vicinity of the dirt road and Seagate Drive. The tide gage and
staff were located on a 40 foot (12 m) long wooden catwalk, constructed by NOS.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
MONUMENTATION: VM#: 16404
AGENCY: PID#: AD6324
SETTING CLASSIFICATION:
BENCH MARK STAMPING: 5171 C 1978
MONUMENTATION: Survey Disk VM#: 7840
AGENCY: PID#: AD6329
SETTING CLASSIFICATION: Concrete Post
The bench mark is 400.0 feet (121.9 m) east of Bench Mark 5171 B 1978, 23.0 feet
(7.0 m) north of the centerline of the dirt road, 21.0 feet (6.4 m) NW of a 1.5
foot (0.5 m) diameter pine tree, 20.0 feet (6.1 m) SE of the most northerly
fence post, and set in the top of a 1.0 foot (0.3 m) diameter concrete post, 0.1
foot (0.1 m) below ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 11/06/1984
Station ID: 8725171 SUPERCEDED DATE: 04/21/2003
Name: OUTER CLAM BAY
FLORIDA
NOAA Chart: 11429 Latitude: 26° 12.7' N
USGS Quad: NAPLES NORTH Longitude: 81° 48.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5171 D 1978
MONUMENTATION: Survey Disk VM#: 7841
AGENCY: PID#: AD6330
SETTING CLASSIFICATION: Copper-coated Steel Rod
The bench mark is 0.1 mile (0.2 km) west of the intersection of U.S. Highway 41
and Seagate Drive, 170.0 feet (51.8 m) north of the NE corner of the North
Naples United Methodist Church, 43.0 feet (13.1 m) north of the centerline of
Seagate Drive, and 1.0 foot (0.3 m) south of United System utility pole No. 611.
The bench mark is at ground level, crimped to a copper-coated steel rod driven
40.0 feet (12.2 m) to refusal, and encased in a PVC pipe and concrete kickblock.
BENCH MARK STAMPING: A 244 1965
MONUMENTATION: Survey Disk VM#: 7842
AGENCY: PID#: AD6331
SETTING CLASSIFICATION: Concrete Post
The bench mark is at the NE corner of the intersection of U.S. Highway 41 and
State Highway S951 (east of the intersection), 129 feet (39 m) east of the
centerline of U.S. Highway 41, 39.0 feet (11.9 m) north of the centerline of
State Highway S951, 3.5 feet (1.1 m) NE of utility pole No. 655, 1.3 feet (0.4
m) south of a witness post, and set into the top of a concrete post, 0.5 foot
(0.2 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 11/06/1984
Station ID: 8725171 SUPERCEDED DATE: 04/21/2003
Name: OUTER CLAM BAY
FLORIDA
NOAA Chart: 11429 Latitude: 26° 12.7' N
USGS Quad: NAPLES NORTH Longitude: 81° 48.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5171 B 1978
MONUMENTATION: Survey Disk VM#: 7843
AGENCY: PID#: AD1249
SETTING CLASSIFICATION: Concrete Post
The bench mark is 0.1 mile (0.2 km) east of Bench Mark 5171 A 1978, 45.5 feet
(13.9 m) north of the centerline of the dirt road, 12.5 feet (3.8 m) east of the
centerline of the west driveway leading to a nursery, 1.2 feet (0.4 m) south of
a fence, and set in the top of a 1.0 foot (0.3 m) diameter concrete post, 0.1
foot (0.1 m) below ground level.
BENCH MARK STAMPING: 5171 A 1978
MONUMENTATION: Survey Disk VM#: 7891
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Post
The bench mark is 50.0 feet (15.2 m) east of the eastern shore of the bay, 420
feet (14.9 m) north of the north edge of the canal, 29.0 feet (8.8 m) east of
the centerline of the dirt road, 6.0 feet (1.8 m) SW of a mangrove swamp, and
set in the top of a 1.0 foot (0.3 m) diameter concrete post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 11/06/1984
Station ID: 8725171 SUPERCEDED DATE: 04/21/2003
Name: OUTER CLAM BAY
FLORIDA
NOAA Chart: 11429 Latitude: 26° 12.7' N
USGS Quad: NAPLES NORTH Longitude: 81° 48.8' W
T I D A L D A T U M S
Tidal datums at OUTER CLAM BAY based on:
LENGTH OF SERIES: 5 MONTHS
TIME PERIOD: APRIL-AUGUST 1978
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8725110 NAPLES
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (05/04/1978) = 1.94
MEAN HIGHER HIGH WATER MHHW = 1.23
MEAN HIGH WATER MHW = 1.02
MEAN TIDE LEVEL MTL = 0.58
MEAN LOW WATER MLW = 0.15
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (04/01/1978) = -0.43
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
0 0.00 0.00
5171 C 1978 6.37 5.35
5171 D 1978 10.10 9.08
A 244 1965 17.66 16.64
5171 B 1978 4.37 3.35
5171 A 1978 2.66 1.64
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 11/06/1984
Station ID: 8725171 SUPERCEDED DATE: 04/21/2003
Name: OUTER CLAM BAY
FLORIDA
NOAA Chart: 11429 Latitude: 26° 12.7' N
USGS Quad: NAPLES NORTH Longitude: 81° 48.8' 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.