U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 07/27/1987
Station ID: 8724499 SUPERCEDED DATE: 04/21/2003
Name: SW END, BOCA CHICA KEY, BOCA CHICA CHANNEL
FLORIDA
NOAA Chart: 11445 Latitude: 24° 33.8' N
USGS Quad: BOCA CHICA KEY Longitude: 81° 43.0' W
To reach the tidal bench marks from the Catholic Church in Key West proceed NE
for 7.3 miles (11.7 km) on U.S. Highway 1 to the road leading to Boca Chica
Naval Air Station, go SW on the road to the main gate of the Naval Air Station
and the weapons storage area. The bench marks are located in the weapons
storage area. The tide gage and staff were located on a short dock in the
western section of the weapons storage area.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: H 329 1970
MONUMENTATION: Survey Disk VM#: 11028
AGENCY: PID#: AA0070
SETTING CLASSIFICATION: Loading Ramp
The bench mark is set in the top of the east end of the loading ramp along the
north side of building #A 1116, 163.9 feet (50.0 m) east of Bench Mark J 329
1970, 22.5 feet (6.9 m) NW of the NE corner of the building, 12 feet (4 m)
north of the north face of the building, 0.5 foot (0.2 m) west of the east end
of the ramp, and 3.5 feet (1.1 m) above the ground.
BENCH MARK STAMPING: J 329 1970
MONUMENTATION: Survey Disk VM#: 11029
AGENCY: PID#: AA0069
SETTING CLASSIFICATION: Concrete Steps
The bench mark is set in the top of the north end of the top step of 5 steps
leading to loading ramp of building #A 1116, 18 feet (5 m) east of the NW corner
of the building, 3.6 feet (1.1 m) north of the north face of the building, 1
foot (0.3 m) south of the north end of the step, and 2.7 feet (0.8 m) above
the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 07/27/1987
Station ID: 8724499 SUPERCEDED DATE: 04/21/2003
Name: SW END, BOCA CHICA KEY, BOCA CHICA CHANNEL
FLORIDA
NOAA Chart: 11445 Latitude: 24° 33.8' N
USGS Quad: BOCA CHICA KEY Longitude: 81° 43.0' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: L 329 1970
MONUMENTATION: Survey Disk VM#: 11030
AGENCY: PID#: AA0065
SETTING CLASSIFICATION: Rock Outcrop
The bench mark is set in the top of a mass of outcropping bedrock about 0.1 mile
(0.2 km) west of the west end of building #A 1116, 30 feet (9 m) east of the
waters edge of a cove, and level with the ground.
BENCH MARK STAMPING: 4499 F 1982
MONUMENTATION: Survey Disk VM#: 11031
AGENCY: PID#: AA1001
SETTING CLASSIFICATION: Rock Outcrop
The bench mark is set in the top of outcropping rock in the weapons storage
area, 105.4 feet (32.1 m) WNW of the NE corner of a chainlink fence, 41.3 feet
(12.6 m) north of the east/west fence, 26.3 feet (8.0 m) north of the centerline
of a track road, and level with the ground.
BENCH MARK STAMPING: 4499 G 1982
MONUMENTATION: Survey Disk VM#: 11032
AGENCY: PID#: AA1000
SETTING CLASSIFICATION: Rock Outcrop
The bench mark is set in the top of outcropping rock in the weapons storage
area, 72.5 feet (22.1 m) SE of the center of the entrance gate to the weapons
storage area, 61.9 feet (18.9 m) south of the centerline of the paved road, and
37.4 feet (11.4 m) east of the chainlink fence on the east side of the weapons
storage area.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 07/27/1987
Station ID: 8724499 SUPERCEDED DATE: 04/21/2003
Name: SW END, BOCA CHICA KEY, BOCA CHICA CHANNEL
FLORIDA
NOAA Chart: 11445 Latitude: 24° 33.8' N
USGS Quad: BOCA CHICA KEY Longitude: 81° 43.0' W
T I D A L D A T U M S
Tidal datums at SW END, BOCA CHICA KEY, BOCA CHICA CHANNEL based on:
LENGTH OF SERIES: 11 MONTHS
TIME PERIOD: APRIL 1971-MARCH 1972
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 (10/06/1971) = 2.33
MEAN HIGHER HIGH WATER MHHW = 1.30
MEAN HIGH WATER MHW = 1.03
MEAN TIDE LEVEL MTL = 0.59
* NATIONAL GEODETIC VERTICAL DATUM NGVD29 = 0.30
MEAN LOW WATER MLW = 0.15
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (04/26/1971) = -0.67
* NGVD reference based on elevations published in Quad 240814, 1971, and NOS
leveling of 1982.
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
H 329 1970 9.74 8.71
J 329 1970 9.29 8.26
L 329 1970 2.05 1.02
4499 F 1982 4.13 3.10
4499 G 1982 3.85 2.82
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 07/27/1987
Station ID: 8724499 SUPERCEDED DATE: 04/21/2003
Name: SW END, BOCA CHICA KEY, BOCA CHICA CHANNEL
FLORIDA
NOAA Chart: 11445 Latitude: 24° 33.8' N
USGS Quad: BOCA CHICA KEY Longitude: 81° 43.0' 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.