U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 07/25/1984
Station ID: 8727348 SUPERCEDED DATE: 04/21/2003
Name: TWIN RIVERS MARINA, CRYSTAL RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 54.3' N
USGS Quad: REDLEVEL Longitude: 82° 38.3' W
To reach the tidal bench marks from the intersection of U.S. Highway 19/98 and
State Road 44 at Crystal River, proceed SE along U.S. Highway 19/98 1.1 miles
(1.8 km) to where State Road 44 picks up again to the right, SW along State Road
44 2.4 miles (3.9 km) to intersection with Suncoast Boulevard, then along State
Road 44 2.3 miles (3.7 km) to Twin Rivers Marina Road, then north along Twin
Rivers Marina Road 0.2 mile (0.3 km) to the marina. The bench marks are located
in the vicinty of the marina and the tide gage and staff were located on the
wooden sea wall at the marina.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: FLORIDA SRD ELEV. 4.70
MONUMENTATION: Survey Disk VM#: 7804
AGENCY: PID#: AL7276
SETTING CLASSIFICATION: Concrete Abutment
The bench mark is set flush in the top of the south concrete culvert abutment
for a creek under Highway S44, 24 feet (7 m) from the east end of the culvert,
18 feet (5 m) south of the centerline of the highway, 12 feet (4 m) from the
west end of the culvert, and 1 foot (0.3 m) below the highway.
BENCH MARK STAMPING: NO 1 1973
MONUMENTATION: Survey Disk VM#: 7800
AGENCY: PID#: AL7280
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set flush in the top of the concrete boat ramp leading from
the NE side of the marina boat shed into the boat basin, 175 feet (53 m) SE of
the Salt River, 32 feet (10 m) NE of the NE side of the marina boat shed, 26
feet (8 m) NE of power pole #400606, 1.5 feet (0.5 m) SW of the boat basin sea
wall and 0.3 foot (0.1 m) NW of the SE side of the ramp.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 07/25/1984
Station ID: 8727348 SUPERCEDED DATE: 04/21/2003
Name: TWIN RIVERS MARINA, CRYSTAL RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 54.3' N
USGS Quad: REDLEVEL Longitude: 82° 38.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 2 1973
MONUMENTATION: Survey Disk VM#: 7801
AGENCY: PID#: AL7279
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set flush in the top south corner of a concrete base for a
steel upright for the boat shed, 3 feet (1 m) inside the boat shed door, 1 foot
(0.3 m) NW of the NW side of the boat ramp, and 1 foot (0.3 m) above the ramp.
BENCH MARK STAMPING: FLORIDA SRD ELEV. 18.32 (SE)
MONUMENTATION: Survey Disk VM#: 7802
AGENCY: PID#: AL7277
SETTING CLASSIFICATION: Concrete Curb
The bench mark is set flush in the top center of a concrete curb abutment on the
SE end of Salt River Bridge for Highway S44, 15 feet (5 m) NE of the centerline
of the highway, 1 foot (0.3 m) SW of a concrete rail, 0.8 foot (0.2 m) SE of the
SE end of the bridge, and 1 foot (0.3 m) above the level of the road.
BENCH MARK STAMPING: FLORIDA SRD ELEV. 18.32 (NW)
MONUMENTATION: Survey Disk VM#: 7803
AGENCY: PID#: AL7278
SETTING CLASSIFICATION: Concrete Curb
The bench mark is set flush in the top center of the concrete curb abutment on
the NW end of the Salt River Bridge for Highway S44, 15 feet (5 m) SW of the
centerline of the highway, 1 foot (0.3 m) NW of a concrete rail, 0.8 foot (0.2
m) NW of the NW end of the bridge, and 0.3 foot (0.1 m) SE of the end of a metal
guard rail.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 07/25/1984
Station ID: 8727348 SUPERCEDED DATE: 04/21/2003
Name: TWIN RIVERS MARINA, CRYSTAL RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 54.3' N
USGS Quad: REDLEVEL Longitude: 82° 38.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 7348 A 1978
MONUMENTATION: Survey Disk VM#: 7805
AGENCY: PID#: AL7751
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is 25.3 feet (7.7 m) NW of the centerline of Highway S44, 22.5
feet (6.9 m) SW of the centerline of a hard top road leading to Twin Rivers
Marina, 15.0 feet (4.6 m) SE of the Twin Rivers Marina sign, and 2.0 feet (0.6
m) NW of metal witness sign nailed to power pole #003. The bench mark is level
with the ground, crimped to a galvanized steel rod driven 14 feet (4 m) to
refusal and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 07/25/1984
Station ID: 8727348 SUPERCEDED DATE: 04/21/2003
Name: TWIN RIVERS MARINA, CRYSTAL RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 54.3' N
USGS Quad: REDLEVEL Longitude: 82° 38.3' W
T I D A L D A T U M S
Tidal datums at TWIN RIVERS MARINA, CRYSTAL RIVER based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: JANUARY-JUNE 1977
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8727520 CEDAR KEY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (05/04/1978) = 4.31
MEAN HIGHER HIGH WATER MHHW = 2.51
MEAN HIGH WATER MHW = 2.17
MEAN TIDE LEVEL MTL = 1.24
MEAN LOW WATER MLW = 0.30
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (02/05/1974) = -1.31
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
FLORIDA SRD ELEV. 4.70 4.93 2.76
NO 1 1973 3.09 0.92
NO 2 1973 5.79 3.62
FLORIDA SRD ELEV. 18.32 (SE) 18.58 16.41
FLORIDA SRD ELEV. 18.32 (NW) 18.59 16.42
7348 A 1978 4.51 2.34
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 07/25/1984
Station ID: 8727348 SUPERCEDED DATE: 04/21/2003
Name: TWIN RIVERS MARINA, CRYSTAL RIVER
FLORIDA
NOAA Chart: 11409 Latitude: 28° 54.3' N
USGS Quad: REDLEVEL Longitude: 82° 38.3' 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.