U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 03/21/1984
Station ID: 8726494 SUPERCEDED DATE: 04/21/2003
Name: LONG KEY, BOCA CIEGA BAY
FLORIDA
NOAA Chart: 11414 Latitude: 27° 45.1' N
USGS Quad: SEMINOLE Longitude: 82° 45.2' W
To reach the tidal bench marks from the intersection of Gulf Boulevard (State
Route 699) and 107th Avenue (Treasure Island Causeway), travel south along Gulf
Boulevard for 1.9 miles (3.1 km) to the intersection of 85th Avenue, then east
on 85th Avenue to Boca Ciega Drive, travel north on Boca Ciega Drive to the St.
Petersburg Beach Pumping Station. The bench marks are on the grounds of the
Gulf Beaches Elementary School grounds between Boca Ciega Drive and Blind Pass
Road, and the tide station was on the sea wall near the pumping station.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: BLIND NO 1 1973
MONUMENTATION: Survey Disk VM#: 6540
AGENCY: PID#: AG0354
SETTING CLASSIFICATION: Concrete Post
The bench mark is set on top of a concrete post flush with the ground, 97.0 feet
(29.6 m) east of the centerline of Blind Pass Road, 47 feet (14.3 m) NE of the
SW corner of the fence around Gulf Beaches Elementary School, 31.3 feet (9.5 m)
north of centerline of 85th Aveune, 3.0 feet (0.9 m) west of the west end of a
gate, and 1.5 feet (0.5 m) north of a 6 foot (1.8 m) high chain link fence.
BENCH MARK STAMPING: BLIND 1973
MONUMENTATION: Survey Disk VM#: 6539
AGENCY: PID#: AG0337
SETTING CLASSIFICATION: Concrete Post
The bench mark is set on a concrete post flush with the ground, 202 feet (61.6
m) SE of the SW corner of the Gulf Beaches Elementary School, 106 feet (32.3 m)
south of a light pole with no number, 21.5 feet (6.6 m) SW of most southerly
palm tree of a group of four, and 16 feet (4.9 m) north of a 6 foot (1.8 m) high
chain link fence.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 03/21/1984
Station ID: 8726494 SUPERCEDED DATE: 04/21/2003
Name: LONG KEY, BOCA CIEGA BAY
FLORIDA
NOAA Chart: 11414 Latitude: 27° 45.1' N
USGS Quad: SEMINOLE Longitude: 82° 45.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BLIND NO 2 1973
MONUMENTATION: Survey Disk VM#: 6541
AGENCY: PID#: AG0355
SETTING CLASSIFICATION: Concrete Post
The bench mark is set in top of a concrete post flush with the ground, 216 feet
(65.8 m) east of the centerline of Blind Pass Road, 140.5 feet (42.8 m) north of
the centerline of 85th Avenue, 130 feet (39.6 m) west of the SW corner of the
most southerly extension of the Gulf Beaches Elementary School Building, 111
feet (33.8 m) SE of the SW corner of the school building, 11.7 feet (3.6 m) west
of a 1.0 foot (0.3 m) diameter palm tree, and 2.0 feet (0.6 m) south of a light
pole with no number.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 03/21/1984
Station ID: 8726494 SUPERCEDED DATE: 04/21/2003
Name: LONG KEY, BOCA CIEGA BAY
FLORIDA
NOAA Chart: 11414 Latitude: 27° 45.1' N
USGS Quad: SEMINOLE Longitude: 82° 45.2' W
T I D A L D A T U M S
Tidal datums at LONG KEY, BOCA CIEGA BAY based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: JULY-SEPTEMBER 1976
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8726486 GULFPORT, BOCA CIEGA BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (10/26/1976) = 3.31
MEAN HIGHER HIGH WATER (MHHW) = 2.31
MEAN HIGH WATER (MHW) = 2.05
MEAN TIDE LEVEL (MTL) = 1.19
MEAN LOW WATER (MLW) = 0.33
MEAN LOWER LOW WATER (MLLW) = 0.00
LOWEST OBSERVED WATER LEVEL (10/22/1976) = -0.94
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
BLIND NO 1 1973 4.55 2.50
BLIND 1973 4.97 2.92
BLIND NO 2 1973 5.93 3.88
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 03/21/1984
Station ID: 8726494 SUPERCEDED DATE: 04/21/2003
Name: LONG KEY, BOCA CIEGA BAY
FLORIDA
NOAA Chart: 11414 Latitude: 27° 45.1' N
USGS Quad: SEMINOLE Longitude: 82° 45.2' 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.