U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8725019 PUBLICATION DATE: 02/26/2004
Name: KEEWAYDIN ISLAND, INSIDE
FL
NOAA Chart: 11430 Latitude: 26° 1.5' N ( 26.02500)
USGS Quad: NAPLES SOUTH Longitude: 81° 46.1' W ( -81.76830)
To reach the tidal bench marks from the US Highway 41 bridge over the Gordon
River in Naples, proceed by boat 9.7 km (6.0 statute mi) south along the
intercoastal waterway to Marker # 36. The station is located on the east side
of Keewaydin Island, on the property of the Naples Cruise Club. The bench marks
are located in the vicinity of the wood dock. The tide gage and staff were
located on the north side of the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 5019 A 1978
DESIGNATION: 872 5019 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 7823
AGENCY: National Ocean Survey (NOS) IDB PID#: AD7974
SETTING CLASSIFICATION: Galvanized steel rod OPUS PID:
LATITUDE: 26° 1.8' N ( 26.03000) LONGITUDE: 81° 46.0' W ( -81.76670)
The primary bench mark is a disk located at the Naples Cruise Club on Keewaydin
Island, 17.89 m (58.7 ft) SE of the SE corner of a picnic shelter area, 8.38 m
(27.5 ft) SE of a 0.30 m (1.0 ft) pine tree, 6.43 m (21.1 ft) south of the dock
and 3.60 m (11.8 ft) west of the shoreline. The bench mark is crimped to a top
of a galvanized steel rod driven 10.1 m (33 ft) to refusal, and encased in a
0.09 m (0.3 ft) diameter steel projector pipe projecting 0.09 m (0.3 ft) above
ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8725019 PUBLICATION DATE: 02/26/2004
Name: KEEWAYDIN ISLAND, INSIDE
FL
NOAA Chart: 11430 Latitude: 26° 1.5' N ( 26.02500)
USGS Quad: NAPLES SOUTH Longitude: 81° 46.1' W ( -81.76830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5019 B 1978
DESIGNATION: 872 5019 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 7824
AGENCY: National Ocean Survey (NOS) IDB PID#: AD7975
SETTING CLASSIFICATION: Concrete post OPUS PID:
LATITUDE: 26° 1.8' N ( 26.03000) LONGITUDE: 81° 46.1' W ( -81.76830)
The bench mark is a disk set at ground level located at the Naples Cruise Club,
65.93 m (216.3 ft) WNW of Bench Mark 5019 A 1978, 7.68 m (25.2 ft) NE of twin
palm trees, 5 m (16 ft) north of the centerline of a path leading from the open
area at the dock westerly to the beach on the Gulf side and 2.47 m (8.1 ft) west
of a 0.09 m (0.3 ft) diameter pine tree.
BENCH MARK STAMPING: 5019 C 1978
DESIGNATION: 872 5019 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 7825
AGENCY: National Ocean Survey (NOS) IDB PID#: AD7976
SETTING CLASSIFICATION: Concrete post OPUS PID:
LATITUDE: 26° 1.8' N ( 26.03000) LONGITUDE: 81° 46.1' W ( -81.76830)
The bench mark is a disk 0.12 m (0.4 ft) below ground level, located at the
Naples Cruise Club, 63.83 m (209.4 ft) WSW of Bench Mark 5019 B 1978, 1.95 m
(6.4 ft) south of the centerline of a path leading from the open area at the
dock westerly to the beach on the Gulf side, 1.25 m (4.1 ft) NW of twin palm
trees and 0.30 m (1.0 ft) north of a witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8725019 PUBLICATION DATE: 02/26/2004
Name: KEEWAYDIN ISLAND, INSIDE
FL
NOAA Chart: 11430 Latitude: 26° 1.5' N ( 26.02500)
USGS Quad: NAPLES SOUTH Longitude: 81° 46.1' W ( -81.76830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5019 D 1978
DESIGNATION: 872 5019 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 7826
AGENCY: National Ocean Survey (NOS) IDB PID#: AD7977
SETTING CLASSIFICATION: Concrete post OPUS PID:
LATITUDE: 26° 1.7' N ( 26.02830) LONGITUDE: 81° 46.1' W ( -81.76830)
The bench mark is a disk set at ground level, located 60.53 m (198.6 ft) west of
Bench Mark 5019 C 1978, 11.43 m (37.5 ft) east of 3 small pine trees, 6.46 m
(21.2 ft) north of the centerline of the path leading to the beach, and 1.22 m
(4.0 ft) south of the vegetation line.
BENCH MARK STAMPING: 5019 E 1978
DESIGNATION: 872 5019 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 7827
AGENCY: National Ocean Survey (NOS) IDB PID#: AD7978
SETTING CLASSIFICATION: Concrete post OPUS PID:
LATITUDE: 26° 1.7' N ( 26.02830) LONGITUDE: 81° 46.1' W ( -81.76830)
The bench mark is a disk set at ground level, located 67.76 m (222.3 ft) WSW of
Bench Mark 5019 D 1978, 61 m (200 ft) east of the shoreline of the Gulf of
Mexico, 17.43 m (57.2 ft) east of SE corner of the picnic shelter, 14.17 m (46.5
ft) south of a 4x 6 deluxe outhouse and 4.79 m (15.7 ft) SSE of a 0.46 m (1.5
ft) pine tree.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8725019 PUBLICATION DATE: 02/26/2004
Name: KEEWAYDIN ISLAND, INSIDE
FL
NOAA Chart: 11430 Latitude: 26° 1.5' N ( 26.02500)
USGS Quad: NAPLES SOUTH Longitude: 81° 46.1' W ( -81.76830)
T I D A L D A T U M S
Tidal datums at KEEWAYDIN ISLAND, INSIDE based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: May 1978 - July 1978
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8725110 NAPLES, GULF OF MEXICO
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.795
MEAN HIGH WATER MHW = 0.721
North American Vertical Datum NAVD88 = 0.610
MEAN SEA LEVEL MSL = 0.441
MEAN TIDE LEVEL MTL = 0.432
MEAN LOW WATER MLW = 0.143
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
5019 A 1978 1.015 0.294
5019 B 1978 1.371 0.650
5019 C 1978 1.562 0.841
5019 D 1978 1.453 0.732
5019 E 1978 2.244 1.523
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8725019 PUBLICATION DATE: 02/26/2004
Name: KEEWAYDIN ISLAND, INSIDE
FL
NOAA Chart: 11430 Latitude: 26° 1.5' N ( 26.02500)
USGS Quad: NAPLES SOUTH Longitude: 81° 46.1' W ( -81.76830)
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.