U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 05/18/1984
Station ID: 8729119 SUPERCEDED DATE: 04/21/2003
Name: SHELL ISLAND, ST. ANDREW BAY
FLORIDA
NOAA Chart: 11391 Latitude: 30° 5.7' N
USGS Quad: BEACON BEACH Longitude: 85° 41.1' W
To reach the tidal bench marks from the boat launch at St. Andrew State Park,
proceed SSE 3.9 miles (6.3 km) to about midpoint, on the NE shoreline and
Captain Andersons Shell Island Tours Pier on Shell Island. The bench marks are
located along and the grassy sand dunes along the middle of Shell Island between
St. Andrew Bay and the Gulf of Mexico on a NW-SE line from the pier, and the
gage site and staff were located on the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 3 1976
MONUMENTATION: Survey Disk VM#: 10013
AGENCY: PID#: BE1354
SETTING CLASSIFICATION: Copper-Coated Steel Rod
The bench mark is on the SE edge of the low ground between two ridges of grassy
covered sand dunes, 283.4 feet (86.4 m) SSE of Bench Mark NO 2 1976, 216 feet
(65.8 m) ENE of a property sign on the gulf side of the island, 5.2 feet (1.6 m)
NW of a line of three, ten foot high, piles, 0.4 foot (0.12 m) NNW of a witness
post. The bench mark is crimped to the top of a 5/8 inch copper-coated steel
rod driven 40.0 feet (12.2 m) to refusal and encased in a PVC protector pipe and
concrete kickblock, 0.2 foot (0.06 m) below ground level.
BENCH MARK STAMPING: NO 1 1976
MONUMENTATION: Survey Disk VM#: 10011
AGENCY: PID#: BE1356
SETTING CLASSIFICATION: Copper-Coated Steel Rod
The bench mark is 314 feet (95.7 m) ESE of Bench Mark NO 2 1976, 54.5 feet (16.6
m) south of the shoreline, 17.0 feet (5.2 m) SW ofthe SE corner and inner end of
the Shell Island Tour Boat Dock, 10.7 feet (3.3 m) SE of the centerline of a
sandy path leading south, 1.0 feet (0.3 m) NNW of a witness post. The bench
mark is crimped to the top of a 5/8 inch diameter coppercoated steel rod driven
40.0 feet (12.2 m) to refusal and encased in a PVC protector pipe and concrete
kickblock, 0.2 foot (0.06 m) below ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 05/18/1984
Station ID: 8729119 SUPERCEDED DATE: 04/21/2003
Name: SHELL ISLAND, ST. ANDREW BAY
FLORIDA
NOAA Chart: 11391 Latitude: 30° 5.7' N
USGS Quad: BEACON BEACH Longitude: 85° 41.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 2 1976
MONUMENTATION: Survey Disk VM#: 10012
AGENCY: PID#: BE1355
SETTING CLASSIFICATION: Copper-Coated Steel Rod
The bench mark is 314 feet (95.7 m) WNW of Bench Mark No 1 1976, 300 feet (91.4
m) west of the dock, 283.4 feet (86.4 m) NNW of Bench Mark NO 3 1976, 80.7 feet
(24.6 m) SW of the remains of a destroyed dock, 12.2 feet (3.7 m) south of a
private property sign, 0.3 feet (0.09 m) SW of a witness post. The bench mark
is crimped to the top of a 5/8 inch copper-coated steel rod driven 40.0 feet
(12.2 m) to refusal encased in a PVC protector and concrete kickblock, 0.8 foot
(0.24 m) below ground level.
BENCH MARK STAMPING: R114 BAY CO 1972
MONUMENTATION: Survey Disk VM#: 10014
AGENCY: PID#: BE1353
SETTING CLASSIFICATION: Concrete Post
The bench mark is on the grassy ridge of sand dunes paralleling the bay, 600.0
feet (183.0 m) SSW of the bay, 580.0 feet (176.8 m) NW of Bench Mark NO 3 1976,
350.0 feet (107.0 m) NNE of the Gulf, 63.9 feet (19.5 m) NE of the NE corner of
the beige cottage on the beach, 20.9 feet (6.4 m) south of a water pump, set
into the top of a 0.3 foot (0.1 m) square concrete post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 05/18/1984
Station ID: 8729119 SUPERCEDED DATE: 04/21/2003
Name: SHELL ISLAND, ST. ANDREW BAY
FLORIDA
NOAA Chart: 11391 Latitude: 30° 5.7' N
USGS Quad: BEACON BEACH Longitude: 85° 41.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: R115 BAY CO 1972
MONUMENTATION: Survey Disk VM#: 10015
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Post
The bench mark is located on a grassy ridge of sand dunes paralleling the beach,
0.6 mile (0.9 km) ESE of Bench Mark R114 BAY CO 1972, 510.0 feet (155.4 m) SE of
the SE and inner corner of the pier on the bay, 490 feet (149.3 m) south of
Bench Mark NO 1 1976, 250.0 feet (76.2 m) north of the gulf shoreline, set into
the top of a 0.3 foot (0.1 m) square concrete post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 05/18/1984
Station ID: 8729119 SUPERCEDED DATE: 04/21/2003
Name: SHELL ISLAND, ST. ANDREW BAY
FLORIDA
NOAA Chart: 11391 Latitude: 30° 5.7' N
USGS Quad: BEACON BEACH Longitude: 85° 41.1' W
T I D A L D A T U M S
Tidal datums at SHELL ISLAND, ST. ANDREW BAY based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: NOVEMBER 1976-FEBRUARY 1977
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8729840 PENSACOLA
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (01/06/1977) = 2.66
MEAN HIGHER HIGH WATER MHHW = 1.32
MEAN HIGH WATER MHW = 1.28
MEAN TIDE LEVEL MTL = 0.67
MEAN LOW WATER MLW = 0.07
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (03/01/1977) = -1.32
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
NO 3 1976 3.85 2.57
NO 1 1976 4.09 2.81
NO 2 1976 2.33 1.05
R114 BAY CO 1972 11.35 10.07
R115 BAY CO 1972 15.17 13.89
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 05/18/1984
Station ID: 8729119 SUPERCEDED DATE: 04/21/2003
Name: SHELL ISLAND, ST. ANDREW BAY
FLORIDA
NOAA Chart: 11391 Latitude: 30° 5.7' N
USGS Quad: BEACON BEACH Longitude: 85° 41.1' 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.