U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 09/24/1985
Station ID: 8720168 SUPERCEDED DATE: 04/21/2003
Name: SIMPSON CREEK
FLORIDA
NOAA Chart: 11488 Latitude: 30° 27.9' N
USGS Quad: MAYPORT Longitude: 81° 25.9' W
To reach the tidal bench marks from the Ferry Terminal on the north side of St.
Johns River and State Highway A1A, proceed north 5.8 miles (9.3 km) to the north
end of a highway bridge over Simpson Creek at Little Talbot Island State Park.
The bench marks are along State Highway A1A. The tide gage and staff were
located 100 feet (30 m) north of the bridge on a catwalk from the west shore.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0168 C 1978
MONUMENTATION: Survey Disk VM#: 5055
AGENCY: PID#: BC1404
SETTING CLASSIFICATION: Copper-clad Steel Rod
The bench mark is 0.3 mile (0.5 km) east of Simpson Creek, 0.1 mile (0.2 km)
west of Bench Mark D 326 1970, 63.6 feet (19.4 m) south of the intersection of
State Highway A1A and a dirt road, 22 feet (7 m) SW of a large twin pine tree,
14.3 feet (4.4 m) east of the dirt road, and 1 foot (0.3 m) west of a witness
post. The bench mark is crimped to a copper-clad steel rod driven 48 feet (15
m), and encased in a PVC pipe 0.4 foot (0.1 m) above ground level.
BENCH MARK STAMPING: 0168 B 1978
MONUMENTATION: Survey Disk VM#: 5054
AGENCY: PID#: BC1403
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is in a roadside park west of Simpson Creek, 0.2 mile (0.3 km)
west of the bridge over Simpson Creek, 125 feet (38 m) south of State Highway
A1A, 19.5 feet (5.9 m) south of the center picnic table of a group of three
tables in the park, and 11 feet (3 m) west of the centerline of a dirt road.
The bench mark is set in a concrete foundation, level with the road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 09/24/1985
Station ID: 8720168 SUPERCEDED DATE: 04/21/2003
Name: SIMPSON CREEK
FLORIDA
NOAA Chart: 11488 Latitude: 30° 27.9' N
USGS Quad: MAYPORT Longitude: 81° 25.9' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: D 326 1970
MONUMENTATION: Survey Disk VM#: 5056
AGENCY: PID#: BC0434
SETTING CLASSIFICATION: Concrete Bridge Walkway
The bench mark is at Myrtle Creek Bridge, 0.4 mile (0.6 km) east of Simpson
Creek, 12.7 feet (3.9 m) south of the centerline of the highway, and 1.0 foot
(0.3 m) east of the west end of the walkway. The bench mark is set on the top
of the west end of the south bridge walkway, 1 foot (0.3 m) above highway level.
BENCH MARK STAMPING: F 326 1970
MONUMENTATION: Survey Disk VM#: 5058
AGENCY: PID#: BC0432
SETTING CLASSIFICATION: Concrete Post
The bench mark is 0.6 mile (1.0 km) west of Simpson Creek near the center of the
inside of a long curve in the highway, 42 feet (13 m) east of the centerline of
the highway, 32 feet (10 m) south of the centerline of a woods road leading
east, 14 feet (4 m) west of a large double trunked tree, and 1.5 feet (0.5 m)
north of a metal witness post. The bench mark is set in a concrete post 0.5
foot (0.2 m) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 09/24/1985
Station ID: 8720168 SUPERCEDED DATE: 04/21/2003
Name: SIMPSON CREEK
FLORIDA
NOAA Chart: 11488 Latitude: 30° 27.9' N
USGS Quad: MAYPORT Longitude: 81° 25.9' W
T I D A L D A T U M S
Tidal datums at SIMPSON CREEK based on:
LENGTH OF SERIES: 5 MONTHS
TIME PERIOD: APRIL-AUGUST 1978
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8720220 MAYPORT
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (07/19/1978) = 7.27
MEAN HIGHER HIGH WATER MHHW = 5.61
MEAN HIGH WATER MHW = 5.27
MEAN TIDE LEVEL MTL = 2.70
* NATIONAL GEODETIC VERTICAL DATUM NGVD29 = 2.27
MEAN LOW WATER MLW = 0.13
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (04/03/1978) = -0.87
* NGVD reference based on elevations published in Quad 300812, 1973, and NOS
leveling of 1978.
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
0168 C 1978 10.38 5.11
0168 B 1978 15.78 10.51
D 326 1970 14.62 9.35
F 326 1970 16.13 10.86
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 09/24/1985
Station ID: 8720168 SUPERCEDED DATE: 04/21/2003
Name: SIMPSON CREEK
FLORIDA
NOAA Chart: 11488 Latitude: 30° 27.9' N
USGS Quad: MAYPORT Longitude: 81° 25.9' 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.