U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 11/21/1984
Station ID: 8727293 SUPERCEDED DATE: 04/21/2003
Name: HALLS RIVER BRIDGE, HALLS RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 48.0' N
USGS Quad: HOMOSASSA Longitude: 82° 36.2' W
To reach the tidal bench marks from the intersection of U.S. Highway 19/98 and
State Road S-490A in Homosassa Springs, proceed west on State Road 490A 1.65
miles (2.6 km) to the bridge over Halls Creek. The bench marks are located
along State Road S-490A. The tide gage and staff were located on center of the
bridge.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 7293 E 1978
MONUMENTATION: Survey Disk VM#: 7774
AGENCY: PID#: AL7708
SETTING CLASSIFICATION: Concrete Post
The bench mark is located 220.0 feet (67.1 m) SW of Bench Mark 7293 D 1978, 56.0
feet (17.1 m) NE of the SW end of a steel guard rail on the SE side of State
Road S-490A, 15.9 feet (4.8 m) SE of the centerline of State Road S-490A and 0.7
foot (0.2 m) NW of the SE edge of the bridge.
BENCH MARK STAMPING: 7293 A 1978
MONUMENTATION: Survey Disk VM#: 7770
AGENCY: PID#: AL7710
SETTING CLASSIFICATION: Concrete Post
The bench mark is located 291.7 feet (88.9 m) SW of Bench Mark 7293 B 1978, 44.0
feet (13.4 m) SE of the centerline of State Road 490A, 10.0 feet (3.0 m) south
of the centerline of a surface road leading to a mobile home park and 1.7 feet
(0.5 m) NE of a witness post nailed to a power pole #421325.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 11/21/1984
Station ID: 8727293 SUPERCEDED DATE: 04/21/2003
Name: HALLS RIVER BRIDGE, HALLS RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 48.0' N
USGS Quad: HOMOSASSA Longitude: 82° 36.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7293 B 1978
MONUMENTATION: Survey Disk VM#: 7771
AGENCY: PID#: AL7709
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is located 339.0 feet (103.3 m) SW of Bench Mark 7293 D 1978,
41.0 feet (12.5 m) SE of the centerline of State Road S-490A, 21.4 feet (6.5 m)
NE of the centerline of the drive leading to an abandoned Hideway Marina and 6.0
feet (1.8 m) SW of a witness post nailed to a power pole #421323. The bench
mark is crimped to a stainless steel rod driven 10 feet (3.0 m) to refusal, and
encased in PVC pipe and a concrete kickblock.
BENCH MARK STAMPING: 7293 C 1978
MONUMENTATION: Survey Disk VM#: 7772
AGENCY: PID#: AL7711
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is located 280 feet (85 m) SW of Bench Mark 7293 A 1978, 43.7
feet (13.3 m) east of the centerline of State Road S-490A, 21.0 feet (6.4 m)
south of the centerline of a surface road leading to a trailer park, 2.4 feet
(0.7 m) south of a witness sign nailed to power pole #11770. The bench mark is
crimped to a galvanized steel rod driven 9 feet (3 m) to refusal, and encased in
PVC pipe and a concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 11/21/1984
Station ID: 8727293 SUPERCEDED DATE: 04/21/2003
Name: HALLS RIVER BRIDGE, HALLS RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 48.0' N
USGS Quad: HOMOSASSA Longitude: 82° 36.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7293 D 1978
MONUMENTATION: Survey Disk VM#: 7773
AGENCY: PID#: AL7707
SETTING CLASSIFICATION: Concrete Post
The bench mark is located 55.9 feet (17.0 m) west of the east end of a steel
guard rail on the north side of State Road S-490A, 15.7 feet (4.8 m) north of
the centerline of State Road S-490A, and 12.2 feet (3.7 m) east of the SW point
of the bridge retaining wall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 11/21/1984
Station ID: 8727293 SUPERCEDED DATE: 04/21/2003
Name: HALLS RIVER BRIDGE, HALLS RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 48.0' N
USGS Quad: HOMOSASSA Longitude: 82° 36.2' W
T I D A L D A T U M S
Tidal datums at HALLS RIVER BRIDGE, HALLS RIVER based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: AUGUST-NOVEMBER 1978
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8726724 CLEARWATER BEACH
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (12/05/1978) = 2.20
MEAN HIGHER HIGH WATER MHHW = 0.72
MEAN HIGH WATER MHW = 0.53
MEAN TIDE LEVEL MTL = 0.30
MEAN LOW WATER MLW = 0.08
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (01/11/1979) = -0.45
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
7293 E 1978 9.54 9.01
7293 A 1978 3.12 2.59
7293 B 1978 3.40 2.87
7293 C 1978 3.75 3.22
7293 D 1978 9.51 8.98
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 11/21/1984
Station ID: 8727293 SUPERCEDED DATE: 04/21/2003
Name: HALLS RIVER BRIDGE, HALLS RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 48.0' N
USGS Quad: HOMOSASSA Longitude: 82° 36.2' 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 (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.