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

                                                                                
Station ID: 8723814                         PUBLICATION DATE:  10/31/2005
Name:       UPPER MATECUMBE KEY,ATLAN. SIDE                   
            FL
NOAA Chart: 11449                           Latitude:   24° 54.9' N (  24.91500)
USGS Quad:  UPPER MATECUMBE KEY             Longitude:  80° 37.9' W ( -80.63170)


To reach the tidal bench marks from the post office in Islamorada, proceed SW on
U.S. Highway 1 for 1.8 km (1.1 mi) to the entrance of the Cheeca Lodge, go SE on
the drive for 0.3 km (0.2 mi) to the lodge.  The bench marks are located along
U.S. Highway 1 and between U.S. Highway 1 and the end of the road.  The tide
gage and staff were located on the Cheeca Lodge fishing pier.


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


                 PRIMARY BENCH MARK STAMPING:  NO 2 1975
                         DESIGNATION:          872 3814 TIDAL 2

MONUMENTATION:           Tidal Station disk                    VM#:        10962
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0838
SETTING CLASSIFICATION:  Concrete step                         OPUS PID:        
LATITUDE:   24° 55.1' N (  24.91830)          LONGITUDE:  80° 38.1' W ( -80.63500)


The primary bench mark is a disk set flush in the first concrete step of the
stairway of the most northwestern two-story apartment building SW of the lodge,
82.42 m (270.4 ft) SSW of the base of a radio tower, 18 m (60 ft) SW of the
centerline of the drive, 8 m (26 ft) SW of the north corner of the apartment
building, 1.62 m (5.3 ft) NW of the NW side of the apartment building, and 0.3 m
(1.0 ft) above ground level.

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

                                                                                
Station ID: 8723814                         PUBLICATION DATE:  10/31/2005
Name:       UPPER MATECUMBE KEY,ATLAN. SIDE                   
            FL
NOAA Chart: 11449                           Latitude:   24° 54.9' N (  24.91500)
USGS Quad:  UPPER MATECUMBE KEY             Longitude:  80° 37.9' W ( -80.63170)


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


                         BENCH MARK STAMPING:  NO 3 1975
                         DESIGNATION:          872 3814 TIDAL 3

MONUMENTATION:           Tidal Station disk                    VM#:        10963
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0839
SETTING CLASSIFICATION:  Concrete step                         OPUS PID:        
LATITUDE:   24° 55.1' N (  24.91830)          LONGITUDE:  80° 38.1' W ( -80.63500)


The bench mark is a disk set flush in the first concrete step of the stairway of
the most southern two-story apartment building SW of the lodge, 30 m (100 ft)
SSE of bench mark NO 2 1975, 18 m (59 ft) SW of the centerline of the drive, 8 m
(26 ft) SW of the north corner of the apartment building, 1.62 m (5.3 ft) NW of
the NW side of the apartment building, and 0.3 m (1.0 ft) above ground level.

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

                                                                                
Station ID: 8723814                         PUBLICATION DATE:  10/31/2005
Name:       UPPER MATECUMBE KEY,ATLAN. SIDE                   
            FL
NOAA Chart: 11449                           Latitude:   24° 54.9' N (  24.91500)
USGS Quad:  UPPER MATECUMBE KEY             Longitude:  80° 37.9' W ( -80.63170)


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


                         BENCH MARK STAMPING:  R 276 1966
                         DESIGNATION:          R 276
                         ALIAS:                872 3814 TIDAL

MONUMENTATION:           Bench Mark disk                       VM#:        10964
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  AA0422
SETTING CLASSIFICATION:  Concrete wall                         OPUS PID:        
LATITUDE:   24° 55.1' N (  24.91830)          LONGITUDE:  80° 38.2' W ( -80.63670)


The bench mark is a disk recessed 0.15 m (0.5 ft) in the NW concrete wall of a 1
m (4 ft) square concrete check valve box for the SE water tank at the Florida
Keys Aqueduct Commission office, 2.3 km (1.4 mi) SW of the post office in
Islamoranda, 29.72 m (97.5 ft) NW of the centerline of U.S. Highway 1, 8.38 m
(27.5 ft) SW of the SW corner of a water tank, 3.54 m (11.6 ft) NW of the west
corner of the office building, 0.3 m (1.0 ft) below U.S. Highway 1 and under a
removable valve cover.

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

                                                                                
Station ID: 8723814                         PUBLICATION DATE:  10/31/2005
Name:       UPPER MATECUMBE KEY,ATLAN. SIDE                   
            FL
NOAA Chart: 11449                           Latitude:   24° 54.9' N (  24.91500)
USGS Quad:  UPPER MATECUMBE KEY             Longitude:  80° 37.9' W ( -80.63170)


                            T I D A L   D A T U M S 


Tidal datums at UPPER MATECUMBE KEY,ATLAN. SIDE based on:

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


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

     MEAN HIGHER HIGH WATER                     MHHW   =  0.696
     MEAN HIGH WATER                            MHW    =  0.655
     North American Vertical Datum              NAVD88 =  0.616
     MEAN SEA LEVEL                             MSL    =  0.361
     MEAN TIDE LEVEL                            MTL    =  0.354
     MEAN LOW WATER                             MLW    =  0.053
     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 2 1975                                   2.003    1.348
     NO 3 1975                                   2.175    1.520
     R 276 1966                                  3.070    2.415


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

                                                                                
Station ID: 8723814                         PUBLICATION DATE:  10/31/2005
Name:       UPPER MATECUMBE KEY,ATLAN. SIDE                   
            FL
NOAA Chart: 11449                           Latitude:   24° 54.9' N (  24.91500)
USGS Quad:  UPPER MATECUMBE KEY             Longitude:  80° 37.9' W ( -80.63170)


                             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.