Superseded Bench Mark Sheet for 8724255, RAMROD KEY FL

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  4

                                                   PUBLICATION DATE:  04/07/1987
Station ID: 8724255                                SUPERCEDED DATE:   04/21/2003
Name:       RAMROD KEY, NILES CHANNEL                         
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 39.6' N
USGS Quad:  SUMMERLAND KEY                         Longitude:        81° 25.4' W


To reach the tidal bench marks from the post office in Summerland Key, proceed
east for 1.4 miles (2.3 km) to the east end of the new bridge over Niles
Channel.  The bench marks are located on the new bridge, the old bridge, and on
Ramrod Key.  The tide gage and staff were located just south of the east 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 1937

MONUMENTATION:           Survey Disk                               VM#:     6860
AGENCY:                                                            PID#:  AA0190
SETTING CLASSIFICATION:  Concrete Wingwall


The bench mark is set in the top of the south concrete wingwall at the east end
of the old U.S. Highway 1 bridge over Niles Channel, 68 feet (21 m) south of the
centerline of the highway, 51.2 feet (15.6 m) SE of Bench Mark NO 2 1937, and 10
feet (3 m) below highway level.



                         BENCH MARK STAMPING:  NO 2 1937

MONUMENTATION:           Survey Disk                               VM#:     6861
AGENCY:                                                            PID#:  AA0191
SETTING CLASSIFICATION:  Concrete Wingwall


The bench mark is set in the top of the south concrete wingwall at the east end
of the old U.S. Highway 1 bridge over Niles Channel, 22.5 feet (6.9 m) south of
the centerline of the highway, and 3 feet (1 m) below highway level.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  4

                                                   PUBLICATION DATE:  04/07/1987
Station ID: 8724255                                SUPERCEDED DATE:   04/21/2003
Name:       RAMROD KEY, NILES CHANNEL                         
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 39.6' N
USGS Quad:  SUMMERLAND KEY                         Longitude:        81° 25.4' W


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


                         BENCH MARK STAMPING:  R 272 1966

MONUMENTATION:           Survey Disk                               VM#:     6862
AGENCY:                                                            PID#:  AA0196
SETTING CLASSIFICATION:  Bedrock


The bench mark is set in the top of a large area of exposed bedrock at the
intersection of Mako Avenue and the old U.S. Highway 1, 365 feet (111 m) north
of and across the old highway from the centerline of U.S. Highway 1, 40 feet (12
m) east of the centerline of Mako Avenue, 25 feet (8 m) north of the centerline
of the old highway, 24.3 feet (7.4 m) ESE of a road sign, 4 feet (1 m) below
U.S. Highway 1 level, 1 foot (0.3 m) below old highway level, and level with the
ground.



                         BENCH MARK STAMPING:  4255 F 1982

MONUMENTATION:           Survey Disk                               VM#:     6863
AGENCY:                                                            PID#:  AA1012
SETTING CLASSIFICATION:  Concrete Guardrail


The bench mark is set flush in the top of the concrete guardrail at the east end
of the new U.S. Highway 1 bridge over Niles Channel, 19.6 feet (6.0 m) south of
the centerline of the bridge, 6.1 feet (1.9 m) west of the SE end of the
concrete guardrail, and 3 feet (1 m) above the road.



                         BENCH MARK STAMPING:  4255 G 1982

MONUMENTATION:           Survey Disk                               VM#:     6864
AGENCY:                                                            PID#:  AA1013
SETTING CLASSIFICATION:  Concrete Guardrail


The bench mark is set flush in the top of the concrete guardrail at the east end
of the new U.S. Highway 1 bridge over Niles Channel, 19.5 feet (5.9 m) south of
the centerline of the bridge, 5.3 feet (1.6 m) west of the NE end of the
concrete guardrail, and 3 feet (1 m) above the road.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  4

                                                   PUBLICATION DATE:  04/07/1987
Station ID: 8724255                                SUPERCEDED DATE:   04/21/2003
Name:       RAMROD KEY, NILES CHANNEL                         
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 39.6' N
USGS Quad:  SUMMERLAND KEY                         Longitude:        81° 25.4' W


                            T I D A L   D A T U M S 


Tidal datums at RAMROD KEY, NILES CHANNEL based on:

     LENGTH OF SERIES:      2 MONTHS
     TIME PERIOD:           JANUARY-FEBRUARY 1974
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8724580 KEY WEST


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

     HIGHEST OBSERVED WATER LEVEL (12/12/1973)         =   2.02
     MEAN HIGHER HIGH WATER                     MHHW   =   1.29
     MEAN HIGH WATER                            MHW    =   1.04
     MEAN TIDE LEVEL                            MTL    =   0.58
   * NATIONAL GEODETIC VERTICAL DATUM           NGVD29 =   0.25
     MEAN LOW WATER                             MLW    =   0.11
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (02/26/1974)         =  -0.53

   * NGVD reference based on elevations published in Quad 240811, 1972, and NOS
     leveling of 1982. 
North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     NO 1 1937                                   3.49      2.45
     NO 2 1937                                  11.66     10.62
     R 272 1966                                  2.07      1.03
     4255 F 1982                                19.51     18.47
     4255 G 1982                                19.52     18.48


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

                                                   PUBLICATION DATE:  04/07/1987
Station ID: 8724255                                SUPERCEDED DATE:   04/21/2003
Name:       RAMROD KEY, NILES CHANNEL                         
            FLORIDA
NOAA Chart: 11445                                  Latitude:         24° 39.6' N
USGS Quad:  SUMMERLAND KEY                         Longitude:        81° 25.4' 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.

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