Bench Mark Sheet for 8724112, OHIO-BAHIA HONDA CHANNEL FL

Superseded Epoch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Small blue map location marker Unpublished bench mark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  6

                                                                                
Station ID: 8724112                         PUBLICATION DATE:  03/09/2004
Name:       OHIO-BAHIA HONDA CHANNEL                          
            FL
NOAA Chart: 11445                           Latitude:   24° 40.2' N (  24.67000)
USGS Quad:  BIG PINE KEY                    Longitude:  81° 15.1' W ( -81.25170)


To reach the tidal bench marks from the post office in Marathon on Vaca Key,
proceed SW on U.S. Highway 1 for 18.0 km (11.2 mi) to the bridge over Ohio-Bahia
Honda Channel.  The bench marks are located at the SW end of the old U.S.
Highway 1 bridge (now a fishing pier) and the SW end of the new U.S. Highway 1
bridge.  The tide gage and staff were located on a pier just SE of the SW end of
the old bridge.


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


                 PRIMARY BENCH MARK STAMPING:  NO 1 1975
                         DESIGNATION:          872 4112 TIDAL 1

MONUMENTATION:           Tidal Station disk                    VM#:         6354
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0947
SETTING CLASSIFICATION:  Concrete bridge wing wall             OPUS PID:        
LATITUDE:   24° 40.2' N (  24.67000)          LONGITUDE:  81° 14.9' W ( -81.24830)


The primary bench mark is a disk set flush in the concrete bridge wing wall at
the SW end of the old bridge (now a fishing pier), 14 m (47 ft) SE of the
centerline of the old highway, 11 m (35 ft) south of the bridge curb, and 2 m (7
ft) below the level of the old bridge.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8724112                         PUBLICATION DATE:  03/09/2004
Name:       OHIO-BAHIA HONDA CHANNEL                          
            FL
NOAA Chart: 11445                           Latitude:   24° 40.2' N (  24.67000)
USGS Quad:  BIG PINE KEY                    Longitude:  81° 15.1' W ( -81.25170)


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


                         BENCH MARK STAMPING:  NO 2 1975
                         DESIGNATION:          872 4112 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:         6355
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0948
SETTING CLASSIFICATION:  Concrete bridge wing wall             OPUS PID:        
LATITUDE:   24° 40.2' N (  24.67000)          LONGITUDE:  81° 14.9' W ( -81.24830)


The bench mark is a disk set flush in the concrete bridge wing wall at the SW
end of the old bridge (now a fishing pier), 10.52 m (34.5 ft) north of bench
mark NO 1 1975, 6.55 m (21.5 ft) south of the north end of the wing wall, 4.72 m
(15.5 ft) SE of the centerline of the old highway, and 1 m (3 ft) below the
level of the old highway.



                         BENCH MARK STAMPING:  NO 3 1975
                         DESIGNATION:          872 4112 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:         6356
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:        
SETTING CLASSIFICATION:  Concrete curb                         OPUS PID:        
LATITUDE:   24° 40.2' N (  24.67000)          LONGITUDE:  81° 14.9' W ( -81.24830)


The bench mark is a disk set flush in the north curb at the west end of the
bridge, 18 m (59 ft) north of bench mark NO 1 1975, 14 m (45 ft) north of bench
mark NO 2 1975, and 3.81 m (12.5 ft) north of the centerline of the highway. 
NOTE: Mark not recovered in 1982 by FLDNR; possibly destroyed.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8724112                         PUBLICATION DATE:  03/09/2004
Name:       OHIO-BAHIA HONDA CHANNEL                          
            FL
NOAA Chart: 11445                           Latitude:   24° 40.2' N (  24.67000)
USGS Quad:  BIG PINE KEY                    Longitude:  81° 15.1' W ( -81.25170)


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


                         BENCH MARK STAMPING:  U 272 1966
                         DESIGNATION:          U 272

MONUMENTATION:           Bench Mark disk                       VM#:         6357
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AA0274
SETTING CLASSIFICATION:  Copper-clad steel rod                 OPUS PID:        
LATITUDE:   24° 40.1' N (  24.66830)          LONGITUDE:  81° 15.4' W ( -81.25670)


The bench mark is a disk located 2.6 km (1.6 mi) NE of the entrance to Bahia
Honda State Park along U.S. Highway 1, 0.6 km (0.4 mi) SW of the SW end of the
U.S. Highway 1 bridge over Ohio-Bahia Honda Channel, 33 m (109 ft) east of cable
pole No. 18610, 14 m (46 ft) SE of the centerline of U.S. Highway 1, 13 m (44
ft) south of mile post No. 38, and 1 m (2 ft) SW of a metal witness post.  The
bench mark is set 1 m (3 ft) below highway level, crimped to the top of a
copper-clad steel rod driven 6.1 m (20 ft) to refusal and encased in a 6-inch
terra cotta pipe.



                         BENCH MARK STAMPING:  4112 E
                         DESIGNATION:          872 4112 E TIDAL FLDT

MONUMENTATION:           Bench Mark disk                       VM#:         6358
AGENCY:                  Florida Department of Transportation
                         (FLDT)                                IDB PID#:  AA0946
SETTING CLASSIFICATION:  Concrete bridge guardrail             OPUS PID:        
LATITUDE:   24° 40.2' N (  24.67000)          LONGITUDE:  81° 14.9' W ( -81.24830)


The bench mark is a disk set flush in the top of the SE concrete bridge
guardrail at the SW end of the bridge, 7.07 m (23.2 ft) SE of the centerline of
the highway, 3.20 m (10.5 ft) NE of the SW end of the guardrail, 0.18 m (0.6 ft)
SW of the abutment, and 1 m (3 ft) above U.S. Highway 1.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8724112                         PUBLICATION DATE:  03/09/2004
Name:       OHIO-BAHIA HONDA CHANNEL                          
            FL
NOAA Chart: 11445                           Latitude:   24° 40.2' N (  24.67000)
USGS Quad:  BIG PINE KEY                    Longitude:  81° 15.1' W ( -81.25170)


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


                         BENCH MARK STAMPING:  4112 F
                         DESIGNATION:          872 4112 F TIDAL

MONUMENTATION:           Reference Mark disk                   VM#:         6359
AGENCY:                  Florida Department of Transportation
                         (FLDT)                                IDB PID#:  AA0945
SETTING CLASSIFICATION:  Concrete bridge guardrail             OPUS PID:        
LATITUDE:   24° 40.2' N (  24.67000)          LONGITUDE:  81° 14.9' W ( -81.24830)


The bench mark is a disk set flush in the top of the concrete bridge guardrail
at the NE end of the bridge, 7.80 m (25.6 ft) NW of the centerline of U.S.
Highway 1, 3.20 m (10.5 ft) SW of the NE end of the guardrail, 0.18 m (0.6 ft)
NE of the abutment, and 1 m (3 ft) above U.S. Highway 1.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8724112                         PUBLICATION DATE:  03/09/2004
Name:       OHIO-BAHIA HONDA CHANNEL                          
            FL
NOAA Chart: 11445                           Latitude:   24° 40.2' N (  24.67000)
USGS Quad:  BIG PINE KEY                    Longitude:  81° 15.1' W ( -81.25170)


                            T I D A L   D A T U M S 


Tidal datums at OHIO-BAHIA HONDA CHANNEL based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           February 1975 - February 1975
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8724580 KEY WEST


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

     North American Vertical Datum              NAVD88 =  0.513
     MEAN HIGHER HIGH WATER                     MHHW   =  0.444
     MEAN HIGH WATER                            MHW    =  0.373
     MEAN SEA LEVEL                             MSL    =  0.210
     MEAN TIDE LEVEL                            MTL    =  0.209
     MEAN LOW WATER                             MLW    =  0.045
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     NO 1 1975                                   1.350    0.977
     NO 2 1975                                   3.171    2.798
     NO 3 1975                                   3.951    3.578
     U 272 1966                                  1.370    0.997
     4112 E                                      5.322    4.949
     4112 F                                      5.578    5.205


Foot Notes:

Bench marks 4112 E and 4112 F are based on one differential leveling connection
and do not meet the quality control standards of the NOS. Therefore, caution
should be used when deriving elevations for these marks. 

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8724112                         PUBLICATION DATE:  03/09/2004
Name:       OHIO-BAHIA HONDA CHANNEL                          
            FL
NOAA Chart: 11445                           Latitude:   24° 40.2' N (  24.67000)
USGS Quad:  BIG PINE KEY                    Longitude:  81° 15.1' W ( -81.25170)


                             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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