U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 11/06/1990
Station ID: 8735587 SUPERCEDED DATE: 04/21/2003
Name: DAUPHIN ISLAND, BAYOU ALOE
ALABAMA
NOAA Chart: 11376 Latitude: 30° 15.5' N
USGS Quad: LITTLE DAUPHIN ISLAND Longitude: 88° 6.8' W
To reach the tidal bench marks from the intersection of Interstate Highway 10
and State Highway 193 (formerly State Highway 163), proceed south on State
Highway 193 for about 26 miles (42 km) to the first east/west cross street (3
blocks north of Bienville Boulevard). The bench marks are along State Highway
193 between Chugae Point to the north and the water tower to the south. The
tide gage and staff were on the two-pile structure off the sea wall owned by
Lamar Oswalt Barnett at the extreme SE corner of Bayou Aloe.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING:
MONUMENTATION: VM#: 10356
AGENCY: PID:
SETTING CLASSIFICATION:
BENCH MARK STAMPING: POT 206 +04.71 1979
MONUMENTATION: Survey Disk VM#: 10353
AGENCY: PID#: BH1746
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in the centerline of State Highway 193, 0.6 mile (1.0 km)
north of Bienville Boulevard, 0.3 mile (0.5 km) south of the south end of the
highway bridge to Dauphin Island, 0.15 mile (0.24 km) north of Bench Mark POT
213 +07.90 1979, 87.0 feet (26.5 m) SW of a fire hydrant, 59.3 feet (18.1 m) SE
of a powerline pole, and level with the road.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 11/06/1990
Station ID: 8735587 SUPERCEDED DATE: 04/21/2003
Name: DAUPHIN ISLAND, BAYOU ALOE
ALABAMA
NOAA Chart: 11376 Latitude: 30° 15.5' N
USGS Quad: LITTLE DAUPHIN ISLAND Longitude: 88° 6.8' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: POT 213 +07.90 1979
MONUMENTATION: Survey Disk VM#: 10354
AGENCY: PID#: BH1747
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in the centerline of State Highway 193, 0.45 mile (0.72
km) north of Bienville Boulevard, 101.0 feet (30.8 m) south of the centerline of
Del Champs Avenue, and level with the road.
BENCH MARK STAMPING: NO STAMPING 1
MONUMENTATION: Chiseled Cross VM#: 10355
AGENCY: PID#: BH1749
SETTING CLASSIFICATION: Water Tower Foundation
The bench mark is a chiseled cross on top of an anchor bolt on the east side of
Dauphin Island Water Tank at the intersection of State Highway 193 and Bienville
Boulevard, 270 feet (82 m) east of the centerline of the boulevard, 86 feet (26
m) west of a power pole, 47 feet (14 m) south of a dirt trail leading east/west,
and 1 foot (0.3 m) above ground.
BENCH MARK STAMPING: 21 D-1 X 1979
MONUMENTATION: Survey Disk VM#: 10357
AGENCY: PID#: BH1748
SETTING CLASSIFICATION: Shallow-set Pipe
The bench mark is in the grassy median of Bienville Boulevard NE of Dauphin
Island Water Tower, 0.05 mile (0.08 km) east along Bienville Boulevard, 34.1
feet (10.4 m) WNW of a metal street light pole, 29.4 feet (9.0 m) north of the
centerline of the eastbound lane of the boulevard, 15.7 feet (14.8 m) south of
the centerline of the westbound lane, 15.0 feet (4.6 m) NNE of a 2-foot (0.6 m)
diameter pine tree with small witness sign, and 0.2 foot (0.1 m) below ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 11/06/1990
Station ID: 8735587 SUPERCEDED DATE: 04/21/2003
Name: DAUPHIN ISLAND, BAYOU ALOE
ALABAMA
NOAA Chart: 11376 Latitude: 30° 15.5' N
USGS Quad: LITTLE DAUPHIN ISLAND Longitude: 88° 6.8' W
T I D A L D A T U M S
Tidal datums at DAUPHIN ISLAND, BAYOU ALOE based on:
LENGTH OF SERIES: 7 MONTHS
TIME PERIOD: MAY-NOVEMBER 1980
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8735180 DAUPHIN ISLAND
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (05/16/1980) = 3.89
MEAN HIGHER HIGH WATER MHHW = 1.66
MEAN HIGH WATER MHW = 1.59
MEAN TIDE LEVEL MTL = 0.85
MEAN LOW WATER MLW = 0.10
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (11/26/1980) = -1.31
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
0 0.00 0.00
POT 206 +04.71 1979 5.61 4.02
POT 213 +07.90 1979 5.62 4.03
NO STAMPING 1 9.78 8.19
21 D-1 X 1979 5.83 4.24
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 11/06/1990
Station ID: 8735587 SUPERCEDED DATE: 04/21/2003
Name: DAUPHIN ISLAND, BAYOU ALOE
ALABAMA
NOAA Chart: 11376 Latitude: 30° 15.5' N
USGS Quad: LITTLE DAUPHIN ISLAND Longitude: 88° 6.8' 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.