U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8731952 PUBLICATION DATE: 07/02/2003
Name: BON SECOUR
AL
NOAA Chart: 11376 Latitude: 30° 18.2' N ( 30.30330)
USGS Quad: FOLEY Longitude: 87° 44.1' W ( -87.73500)
To reach the tidal bench marks from the intersection of U.S. Interstate 10 and
Gulf Shores Parkway east of Mobile Bay, proceed 39 km (24 mi) south on Gulf
Shores Parkway to Baldwin County Road 10, then west on County Road 10 to Bon
Secour Post Office, and continue south on County Road 10 for another 1.9 km (1.2
mi) to Bon Secour Fisheries. The bench marks are near the Bon Secour Fisheries
facilities. The tide gage and staff were on the west side of the Bon Secour
Fisheries pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1952 A 1980
DESIGNATION: 873 1952 TIDAL A
MONUMENTATION: Tidal Station disk VM#: 10344
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 30° 18.2' N ( 30.30330) LONGITUDE: 87° 44.1' W ( -87.73500)
The primary bench mark is a disk set flush in a concrete foundation pad on the
north side of the Bon Secour Fisheries building, 41 m (134 ft) south of a large
oak tree, 22 m (72 ft) south of the centerline of the paved road, 5 m (16 ft) SE
of the NW corner of the Bon Secour Fisheries building, 2 m (8 ft) south of the
NE corner of the concrete platform supporting four steps, and 2 m (7 ft) east of
the steps.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8731952 PUBLICATION DATE: 07/02/2003
Name: BON SECOUR
AL
NOAA Chart: 11376 Latitude: 30° 18.2' N ( 30.30330)
USGS Quad: FOLEY Longitude: 87° 44.1' W ( -87.73500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 12 RWH 1976
DESIGNATION: 873 1952 12 RWH
MONUMENTATION: Survey disk VM#: 10342
AGENCY: U.S. Geological Survey (USGS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 30° 18.2' N ( 30.30330) LONGITUDE: 87° 44.1' W ( -87.73500)
The bench mark is a disk set in a concrete monument 0.3 km (0.2 mi) west of the
Bon Secour Fisheries building, at the end of a paved and dirt road, 32.86 m
(107.8 ft) south of the SW corner of a white frame cottage, 24 m (79 ft) NW of
the centerline of an east-west road, 12.31 m (40.4 ft) east of a dirt drive
north along a small canal, 1 m (3 ft) SE of a 0.24 m (0.8 ft) diameter pine tree
with witness sign, and 0.1 m (0.2 ft) above ground level.
BENCH MARK STAMPING: 1952B 1980
DESIGNATION: 873 1952 TIDAL B
MONUMENTATION: Tidal Station disk VM#: 10345
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: BBBG81
LATITUDE: 30° 18.2' N ( 30.30330) LONGITUDE: 87° 44.1' W ( -87.73500)
The bench mark is a disk located on the north side of the paved road, 116 m (382
ft) west of bench mark 1952 A 1980, 25 m (82 ft) SW of the SW corner of a
residence, 9 m (30 ft) north of the centerline of the paved road, and 0.3 m (1.0
ft) north of utility pole #AWP10R60SP0 with witness sign. The bench mark is set
9 cm (0.3 ft) below ground level, crimped to the top of a stainless steel rod
driven 16.8 m (55.0 ft) to refusal, and encased in a 4-inch PVC pipe and
concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8731952 PUBLICATION DATE: 07/02/2003
Name: BON SECOUR
AL
NOAA Chart: 11376 Latitude: 30° 18.2' N ( 30.30330)
USGS Quad: FOLEY Longitude: 87° 44.1' W ( -87.73500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 7 1986
DESIGNATION: 873 1952 TIDAL 7
MONUMENTATION: Tidal Station disk VM#: 10346
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete slab OPUS PID:
LATITUDE: 30° 18.2' N ( 30.30330) LONGITUDE: 87° 44.1' W ( -87.73500)
The bench mark is a disk set flush in a 1 m x 2 m (3 ft x 5 ft) concrete slab in
a park area of Bon Secour Fisheries, 30.02 m (98.5 ft) ESE of the SE corner of
Bon Secour Fisheries fish house, 22.31 m (73.2 ft) north of a five pile dolphin
at the SW corner of the Bon Secour Fisheries pier, and 20.88 m (68.5 ft) south
of a power pole south of an abandoned building.
BENCH MARK STAMPING: NO 8 1986
DESIGNATION: 873 1952 TIDAL 8
MONUMENTATION: Tidal Station disk VM#: 10347
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 30° 18.2' N ( 30.30330) LONGITUDE: 87° 44.1' W ( -87.73500)
The bench mark is a disk recessed in an old house foundation on property owned
by the Adams family located across the paved road and just north of Bon Secour
Fisheries, 10.70 m (35.1 ft) south of the larger of two oak trees, 9.81 m (32.2
ft) north of a 0.61 m (2.0 ft) diameter tree, 9 m (29 ft) west of power pole
#972 on the west side of County Road 10, and 0.15 m (0.5 ft) below the surface
of the foundation.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8731952 PUBLICATION DATE: 07/02/2003
Name: BON SECOUR
AL
NOAA Chart: 11376 Latitude: 30° 18.2' N ( 30.30330)
USGS Quad: FOLEY Longitude: 87° 44.1' W ( -87.73500)
T I D A L D A T U M S
Tidal datums at BON SECOUR based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: September 1986 - November 1986
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8729840 PENSACOLA, PENSACOLA BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.470
MEAN HIGH WATER MHW = 0.459
MEAN TIDE LEVEL MTL = 0.236
MEAN SEA LEVEL MSL = 0.234
MEAN LOW WATER MLW = 0.013
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1952 A 1980 1.283 0.824
12 RWH 1976 1.310 0.851
1952B 1980 0.793 0.334
NO 7 1986 1.172 0.713
NO 8 1986 2.162 1.703
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8731952 PUBLICATION DATE: 07/02/2003
Name: BON SECOUR
AL
NOAA Chart: 11376 Latitude: 30° 18.2' N ( 30.30330)
USGS Quad: FOLEY Longitude: 87° 44.1' W ( -87.73500)
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 NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.
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.