U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
To reach the tidal bench marks from I-1O East, proceed east on Duval St for .43
KM (.27 MI) to Broad St, then turn right and proceed south on Broad St for .71
KM (.44 MI) to the main road for the Coast Guard section Mobile on the left. The
bench marks are located at various location around the coast guard base. The
tide station is located on the pier of the Coast Guard base.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6897 A 2007
DESIGNATION: 873 6897 A
ALIAS: 6897 A
MONUMENTATION: Flange-encased Rod VM#: 18507
AGENCY: National Ocean Service IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: BBFW30
LATITUDE: 30° 39.0' N ( 30.64944) LONGITUDE: 88° 3.5' W ( -88.05903)
The primary bench mark is flange-encased rod located 37.7 m (123.69 ft) south of
a concrete slab marking the player dugout, 28.8 m (94.5 ft) east of the north
edge of the small boat ramp, and 5.5 m (18.04 ft) SE of the corner post marking
right field of the baseball field. The bench mark is crimped to a stainless
steel rod driven 18.3 m (60 ft) to refusal, and encased in a 6 inch PVC pipe
with concrete kickblock. Note - the bench mark is covered with an aluminum
access cover bearing the mark stamping.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: AL14 A 98
DESIGNATION: AL14 A
ALIAS: AL14 A
MONUMENTATION: Bench Mark disk VM#: 18508
AGENCY: COE IDB PID:
SETTING CLASSIFICATION: Concrete Boat Ramp OPUS PID:
LATITUDE: 30° 39.0' N ( 30.64928) LONGITUDE: 88° 3.5' W ( -88.05861)
The bench mark is a disk located in the top of a concrete on the shoulder of the
ramp between the boat ramp and fire boat dock, 12.8 m (42.0 ft), 130 degrees
south of the south edge of the small boat ramp, 4.1m (13.5 ft), 40 degrees NE of
a light/power pole, 3.8 m (12.5 ft), 315 degrees NE of the north edge of the
fire boat dock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: AL14 B 98
DESIGNATION: AL14 B
ALIAS: AL14 B
MONUMENTATION: Bench Mark disk VM#: 18509
AGENCY: COE IDB PID:
SETTING CLASSIFICATION: Concrete Median OPUS PID#: BBFW31
LATITUDE: 30° 38.9' N ( 30.64892) LONGITUDE: 88° 3.6' W ( -88.05989)
The bench mark is a disk located in the median of two roads running N/S on the
west side of the baseball field on the coast guard base, 30.2 m (99.1ft) SW of
the concrete slab marking a player dougout, 24.3 m (79.7 ft) west of the corner
side walk on the SE side of a building with 2 garge bays, 15.7 m (51.5 ft) south
of the left field fence line of the baseball field.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6897 B 2007
DESIGNATION: 873 6897 B
ALIAS: 6897 B
MONUMENTATION: Flange-encased Rod VM#: 18510
AGENCY: IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 30° 39.0' N ( 30.64922) LONGITUDE: 88° 3.6' W ( -88.06028)
The bench mark is a flange-encased rod located north of the left field corner of
the baseball field on the Coast Guard base, 23.9 m (78.4 ft) east of a fire
plug, 19.7 m (64.6 ft) south of the concrete road running east/west behind the
field, and 1.6 m (5.2 ft) north of the corner post in far left field. The bench
mark is a stainless steel rod driven 12.2 m (40 ft) encased in a 6 inch PVC pipe
with a concrete kickblock. Note - the mark covered with an aluminum access
cover bearing the stamping of the mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6897 C 2007
DESIGNATION: 873 6897 C
ALIAS: 6897 C
MONUMENTATION: Flange-encased Rod VM#: 18511
AGENCY: IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: BBCV28
LATITUDE: 30° 39.0' N ( 30.65019) LONGITUDE: 88° 3.6' W ( -88.05983)
The bench mark is a flange-encased rod located north across the street on the
east side of the administration building on the Coast Guard base mobile sector,
23 m (75.5 ft) SE of the SE corner of the administrative building, 14 m (45.9
ft) NE of a concrete communications building, 7.7 m (25.3ft) SW of a concrete
slab of a gazebo. The bench mark is crimped to a stainless steel rod driven
18.3 m (60 ft) to refusal, and encased in a 6 inch PVC pipe with a concrete
kickblock. Note - the bench mark is covered with an aluminum access cover
bearing the mark stamping.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: TAW
DESIGNATION: TAW
ALIAS: 6897 F
MONUMENTATION: Bench Mark disk VM#: 18512
AGENCY: COE IDB PID:
SETTING CLASSIFICATION: Concrete Wharf Road OPUS PID#: BBFW32
LATITUDE: 30° 39.0' N ( 30.65072) LONGITUDE: 88° 3.6' W ( -88.05967)
The bench mark is a disk set into the concrete road leading to the main wharf at
the Coast Guard sector Mobile base, 8.8 m (28.9 ft) NE of the concrete wing at
the west end of the wharf bulkhead, 7.7 m (25.3 ft) NNW of a light pole, and 3.8
m (12.5 ft) north of the wharf bulkhead.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: GBC 92-7
DESIGNATION: GBC
ALIAS: 6897 G
MONUMENTATION: Bench Mark disk VM#: 18513
AGENCY: COE IDB PID:
SETTING CLASSIFICATION: Concrete Wharf OPUS PID:
LATITUDE: 30° 39.1' N ( 30.65181) LONGITUDE: 88° 3.5' W ( -88.05753)
The bench mark is a disk set in the concrete wharf located at SE most corner of
the main wharf at Coast Guard Sector Mobile, 2.0 m (6.6 ft) west of the east
edge of the bulkhead, 1.3 m (4.3 ft) east of a large bollard, 0.6 m (2.0 ft)
north of the face of the wharf.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 8 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: AL9226 MS2387
DESIGNATION: LAWLER
MONUMENTATION: Survey disk VM#: 19537
AGENCY: DNR IDB PID:
SETTING CLASSIFICATION: Concrete Road OPUS PID:
LATITUDE: 30° 39.0' N ( 30.65019) LONGITUDE: 88° 3.6' W ( -88.06078)
The bench mark is a survey disk located just inside the gate of the Coast Guard
Sector Mobile Base, 14.5 m (47.6 ft) NE of the southern most gate post, 14 m
(45.9 ft) SE of the northern most gate post, 11.4 m (37.4 ft) east of the main
gate building.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 9 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
T I D A L D A T U M S
Tidal datums at COAST GUARD SECTOR MOBILE, MOBILE BAY based on:
LENGTH OF SERIES: 120 MONTHS
TIME PERIOD: Jul 2008 - Jun 2012 & Oct 2012 - Sept 2018
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8737048 MOBILE STATE DOCKS, MOBILE RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (10/08/2017) = 2.157
MEAN HIGHER HIGH WATER MHHW = 0.517
MEAN HIGH WATER MHW = 0.493
MEAN TIDE LEVEL MTL = 0.260
MEAN SEA LEVEL MSL = 0.257
North American Vertical Datum NAVD88 = 0.162
MEAN LOW WATER MLW = 0.027
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (09/16/2020) = -2.128
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6897 A 2007 1.274 0.781
AL14 A 98 1.104 0.611
AL14 B 98 2.228 1.735
6897 B 2007 1.917 1.424
6897 C 2007 3.280 2.787
TAW 3.757 3.264
GBC 92-7 3.766 3.274
AL9226 MS2387 3.498 3.005
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 10 of 10
Station ID: 8736897 PUBLICATION DATE: 11/16/2020
Name: COAST GUARD SECTOR MOBILE, MOBILE BAY
AL
NOAA Chart: 11376 Latitude: 30° 38.9' N ( 30.64831)
USGS Quad: MOBILE Longitude: 88° 3.5' W ( -88.05831)
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.