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Bench Mark Sheet for 8733821, Point Clear, Mobile Bay AL

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                                                
Station ID: 8733821                         PUBLICATION DATE:  03/22/2011
Name:       POINT CLEAR, MOBILE BAY                           
            AL
NOAA Chart: 11376                           Latitude:   30° 29.2' N (  30.48664)
USGS Quad:  POINT CLEAR                     Longitude:  87° 56.1' W ( -87.93453)


In Fairhope, from the intersection of Fairhope Avenue and County Road 3, proceed
west on Fairhope Avenue for approximately 0.80 km (0.5 mi) to the intersection
with US-98 Alternate (US-98 ALT). Proceed South on US-98 ALT for approximately
4.8 km (3.0 mi) to the entrance of the Grand Hotel Marina. The tide station is
located at the west end of the marina's north jetty. The bench marks are in the
vicinity of the marina and on the south side of the Grand Hotel property.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  3821 A 2010
                         DESIGNATION:          873 3821 A

MONUMENTATION:           Bench Mark disk                       VM#:        19784
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  concrete bulkhead                     OPUS PID:        
LATITUDE:   30° 29.2' N (  30.48658)          LONGITUDE:  87° 56.1' W ( -87.93453)


The primary bench mark is a disc set flush in the SW end of the north jetty's
concrete bulkhead, 4.51 m (14.8 ft) south of the north face of the jetty, 4.04 m
(13.3 ft) east of the SW corner of the jetty, 3.37 m (11.1 ft) east of the green
navigational light on the SW corner of the jetty, and 0.27 m (0.9 ft) north of
the south face of the jetty.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 8733821                         PUBLICATION DATE:  03/22/2011
Name:       POINT CLEAR, MOBILE BAY                           
            AL
NOAA Chart: 11376                           Latitude:   30° 29.2' N (  30.48664)
USGS Quad:  POINT CLEAR                     Longitude:  87° 56.1' W ( -87.93453)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  3821 B 2010
                         DESIGNATION:          873 3821 B

MONUMENTATION:           Bench Mark disk                       VM#:        19785
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  concrete bulkhead                     OPUS PID:        
LATITUDE:   30° 29.2' N (  30.48631)          LONGITUDE:  87° 56.0' W ( -87.93292)


The bench mark is a disc set on the north side of the marina between two corners
in the concrete bulkhead for the boat slips, 49.33 m (161.8 ft) WNW of the east
corner of the sea wall, 34.35 , (112.7 ft) ESE from the west corner of the sea
wall, 21.50 m (70.5 ft) SSW of power pole number 32825, and 3.83 m (12.6 ft)
south of the third lamp post from the NW.



                         BENCH MARK STAMPING:  3821 C 2010
                         DESIGNATION:          873 3821 C

MONUMENTATION:           Bench Mark disk                       VM#:        19786
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  bridge abutment                       OPUS PID:        
LATITUDE:   30° 29.1' N (  30.48583)          LONGITUDE:  87° 55.9' W ( -87.93242)


The bench mark is a disc set flush in the NW bridge abutment for the bridge over
Point Clear creek, 40.55 m (133.0 ft) south of a fire hydrant on the south side
of the entrance to the marina, 25.08 m (82.3 ft) NNE of power pole number 32830,
17.11 m (56.1 ft) west of power pole number 32831, 6.55 m (21.5 ft) west of the
centerline of US-98 Alternate, and 1.55 m (5.1 ft) NW of the NW corner of the
bridge.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 8733821                         PUBLICATION DATE:  03/22/2011
Name:       POINT CLEAR, MOBILE BAY                           
            AL
NOAA Chart: 11376                           Latitude:   30° 29.2' N (  30.48664)
USGS Quad:  POINT CLEAR                     Longitude:  87° 56.1' W ( -87.93453)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  3821 D 2010
                         DESIGNATION:          873 3821 D

MONUMENTATION:           Bench Mark disk                       VM#:        19787
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  concrete seawall                      OPUS PID:        
LATITUDE:   30° 28.9' N (  30.48242)          LONGITUDE:  87° 56.1' W ( -87.93450)


The bench mark is a disc set flush in the concrete seawall near the SE corner of
the Grand Hotel, 49.77 m (163.3 ft) ESE of the flagpole, 27.77 m (91.1 ft) south
of the SE corner of the hotel building, 3.88 m (12.7 ft) SSW of the outside edge
of the east end of the seawall, where the concrete meets the brick and where the
wooden fence ends, and 0.38 m (1.2 ft) NNE of the seaward edge of the seawall.



                         BENCH MARK STAMPING:  3821 E 2010
                         DESIGNATION:          873 3821 E

MONUMENTATION:           Bench Mark disk                       VM#:        19788
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  concrete seawall                      OPUS PID#: BBCD23
LATITUDE:   30° 29.0' N (  30.48267)          LONGITUDE:  87° 56.2' W ( -87.93689)


The bench mark is a disc set flush in the concrete seawall at the SW end of the
wooden fence on the south side of the Grand Hotel, 24.88 m (81.6 ft) south of
the point directly between two doors of a building with restrooms at either end,
14.34 m (47.0 ft) ESE of the south corner of a gazebo, and 0.45 m (1.5 ft) NW of
the seaward side of the seawall.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 8733821                         PUBLICATION DATE:  03/22/2011
Name:       POINT CLEAR, MOBILE BAY                           
            AL
NOAA Chart: 11376                           Latitude:   30° 29.2' N (  30.48664)
USGS Quad:  POINT CLEAR                     Longitude:  87° 56.1' W ( -87.93453)


                            T I D A L   D A T U M S 


Tidal datums at POINT CLEAR, MOBILE BAY based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           December 2010 - January 2011
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8735180 DAUPHIN ISLAND, MOBILE BAY


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     MEAN HIGH WATER                            MHW    =  0.463
     MEAN HIGHER HIGH WATER                     MHHW   =  0.457
     MEAN SEA LEVEL                             MSL    =  0.238
     MEAN TIDE LEVEL                            MTL    =  0.234
     MEAN LOW WATER                             MLW    =  0.005
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     3821 A 2010                                 1.417    0.954
     3821 B 2010                                 1.407    0.944
     3821 C 2010                                 1.248    0.785
     3821 D 2010                                 1.847    1.384
     3821 E 2010                                 1.694    1.231


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                                                
Station ID: 8733821                         PUBLICATION DATE:  03/22/2011
Name:       POINT CLEAR, MOBILE BAY                           
            AL
NOAA Chart: 11376                           Latitude:   30° 29.2' N (  30.48664)
USGS Quad:  POINT CLEAR                     Longitude:  87° 56.1' W ( -87.93453)


                             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.

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Products available at 8733821 Point Clear, Mobile Bay, AL

Revised: 10/15/2013
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services