U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 8723852                         PUBLICATION DATE:  04/01/2004
Name:       LOWER MATECUMBE KEY, FLA. BAY                     
            FL
NOAA Chart: 11452                           Latitude:   24° 51.9' N (  24.86500)
USGS Quad:  LOWER MATECUMBE KEY             Longitude:  80° 43.0' W ( -80.71670)


To reach the tidal bench marks proceed 11.7 km (7.3 mi) SW from the post office
in Islamorada on U.S. Highway 1, thence 0.2 km (0.1 mi) north along a private
driveway to the Game Fish Resort Motel.  The bench marks are in the vicinity of
the motel along the seawall and a hurricane fence north of the motel.  The tide
gage and staff were located on a small dock near the boat ramp SW of the motel.


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


                 PRIMARY BENCH MARK STAMPING:  F 328 1970
                         DESIGNATION:          F 328

MONUMENTATION:           Bench Mark disk                       VM#:        10932
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  AA0405
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   24° 51.9' N (  24.86500)          LONGITUDE:  80° 43.0' W ( -80.71670)


The primary bench mark is a disk set in top of a rock ledge at the water's edge,
22.04 m (72.3 ft) NW of the NW corner of the most northerly motel unit, 7.10 m
(23.3 ft) NW of bench mark E 328 1970, 4.11 m (13.5 ft) SE of the NW end of a
hurricane fence along the side of the motel property, 2.90 m (9.5 ft) south of a
fence, 0.30 m (1.0 ft) west of the west edge of a sea wall, and 0.30 m (1.0 ft)
below the sea wall.

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

                                                                                
Station ID: 8723852                         PUBLICATION DATE:  04/01/2004
Name:       LOWER MATECUMBE KEY, FLA. BAY                     
            FL
NOAA Chart: 11452                           Latitude:   24° 51.9' N (  24.86500)
USGS Quad:  LOWER MATECUMBE KEY             Longitude:  80° 43.0' W ( -80.71670)


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


                         BENCH MARK STAMPING:  B 328 1970
                         DESIGNATION:          B 328

MONUMENTATION:           Bench Mark disk                       VM#:        10928
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  AA0402
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   24° 51.9' N (  24.86500)          LONGITUDE:  80° 43.0' W ( -80.71670)


The bench mark is a disk set in top of the rock ledge at the water's edge, 23.26
m (76.3 ft) west of the SW corner of the most northerly unit of the Game Fish
Resort Motel, 6.80 m (22.3 ft) south of the south edge of a concrete boat ramp,
0.12 m (0.4 ft) west of the west face of the sea wall, and 0.61 m (2.0 ft) below
the top of the sea wall.

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

                                                                                
Station ID: 8723852                         PUBLICATION DATE:  04/01/2004
Name:       LOWER MATECUMBE KEY, FLA. BAY                     
            FL
NOAA Chart: 11452                           Latitude:   24° 51.9' N (  24.86500)
USGS Quad:  LOWER MATECUMBE KEY             Longitude:  80° 43.0' W ( -80.71670)


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


                         BENCH MARK STAMPING:  D 328 1970
                         DESIGNATION:          D 328

MONUMENTATION:           Bench Mark disk                       VM#:        10930
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  AA0403
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   24° 51.8' N (  24.86330)          LONGITUDE:  80° 43.0' W ( -80.71670)


The bench mark is a disk set in top of a bedrock outcrop 10 m (34 ft) east of a
sea wall, 10.15 m (33.3 ft) SE of bench mark E 328 1970, 5 m (17 ft) NW of the
NW corner of a metal unit, 3 m (9 ft) south of a hurricane fence, and level with
the ground.

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

                                                                                
Station ID: 8723852                         PUBLICATION DATE:  04/01/2004
Name:       LOWER MATECUMBE KEY, FLA. BAY                     
            FL
NOAA Chart: 11452                           Latitude:   24° 51.9' N (  24.86500)
USGS Quad:  LOWER MATECUMBE KEY             Longitude:  80° 43.0' W ( -80.71670)


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


                         BENCH MARK STAMPING:  E 328 1970
                         DESIGNATION:          E 328

MONUMENTATION:           Bench Mark disk                       VM#:        10931
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  AA0400
SETTING CLASSIFICATION:  Bedrock                               OPUS PID:        
LATITUDE:   24° 51.9' N (  24.86500)          LONGITUDE:  80° 43.0' W ( -80.71670)


The bench mark is a disk set in top of a bedrock outcrop 23 m (75 ft) north of
the north edge of a boat ramp, 15.30 m (50.2 ft) NW of the NW corner of the most
northerly motel unit, 11 m (36 ft) SE of the NW end of a hurricane fence around
the motel property, 10.15 m (33.3 ft) NW of bench mark D 328 1970, 7.10 m (23.3
ft) SE of bench mark F 328 1970, 4 m (14 ft) south of the fence, 2.87 m (9.4 ft)
east of the east face of a sea wall, and level with the ground.



                         BENCH MARK STAMPING:  3852 F 1982
                         DESIGNATION:          872 3852 F TIDAL
                         ALIAS:                 

MONUMENTATION:           Tidal Station disk                    VM#:        10933
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0804
SETTING CLASSIFICATION:  Concrete bulkhead                     OPUS PID:        
LATITUDE:   24° 51.9' N (  24.86500)          LONGITUDE:  80° 43.0' W ( -80.71670)


The bench mark is a disk set in a concrete bulkhead 16 m (53 ft) WSW of the NW
corner of the motel, 7.74 m (25.4 ft) NNE of the east corner of a pavilion, 1.83
m (6.0 ft) SW of the center of a boat ramp, and about level with the ground.



                         BENCH MARK STAMPING:  3852 G 1982
                         DESIGNATION:          872 3852 G TIDAL
                         ALIAS:                 

MONUMENTATION:           Tidal Station disk                    VM#:        10934
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  AA0803
SETTING CLASSIFICATION:  Concrete base for sign                OPUS PID:        
LATITUDE:   24° 51.9' N (  24.86500)          LONGITUDE:  80° 43.0' W ( -80.71670)


The bench mark is a disk set in the concrete base of the sign for the Game Fish
Resort motel, 32.10 m (105.3 ft) NW of the centerline of U.S. Highway 1, 25.45 m
(83.5 ft) NE of the concrete power pole No. 889, 13.72 m (45.0 ft) SW of the
centerline of the road to the motel,  0.12 m (0.4 ft) SE of the SE steel support
for the Game Fish Resort motel sign, and 0.61 m (2.0 ft) below the level of the
highway.

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

                                                                                
Station ID: 8723852                         PUBLICATION DATE:  04/01/2004
Name:       LOWER MATECUMBE KEY, FLA. BAY                     
            FL
NOAA Chart: 11452                           Latitude:   24° 51.9' N (  24.86500)
USGS Quad:  LOWER MATECUMBE KEY             Longitude:  80° 43.0' W ( -80.71670)


                            T I D A L   D A T U M S 


Tidal datums at LOWER MATECUMBE KEY, FLA. BAY based on:

     LENGTH OF SERIES:      1 YEAR
     TIME PERIOD:           January 1971 - December 1971
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8724580 KEY WEST


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

     HIGHEST OBSERVED WATER LEVEL (03/30/1971)         =  0.479
     North American Vertical Datum              NAVD88 =  0.396
     MEAN HIGHER HIGH WATER                     MHHW   =  0.299
     MEAN HIGH WATER                            MHW    =  0.257
     MEAN TIDE LEVEL                            MTL    =  0.142
     MEAN SEA LEVEL                             MSL    =  0.139
     MEAN LOW WATER                             MLW    =  0.027
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (02/10/1971)         = -0.389

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     F 328 1970                                  0.440    0.183
     B 328 1970                                  0.326    0.069
     D 328 1970                                  0.589    0.332
     E 328 1970                                  0.557    0.300
     3852 F 1982                                 0.690    0.433
     3852 G 1982                                 1.123    0.866


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

                                                                                
Station ID: 8723852                         PUBLICATION DATE:  04/01/2004
Name:       LOWER MATECUMBE KEY, FLA. BAY                     
            FL
NOAA Chart: 11452                           Latitude:   24° 51.9' N (  24.86500)
USGS Quad:  LOWER MATECUMBE KEY             Longitude:  80° 43.0' W ( -80.71670)


                             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.