U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8724436 PUBLICATION DATE: 02/05/2004
Name: BIRD KEY
FL
NOAA Chart: 11445 Latitude: 24° 35.3' N ( 24.58830)
USGS Quad: BOCA CHICA KEY Longitude: 81° 38.3' W ( -81.63830)
To reach the tidal bench marks from the U.S. Highway 1 bridge between Big
Coppitt Key and Saddlebunch Keys, proceed SSE by boat for 1.6 km (1.0 statute
mi) to the northern end of Bird Key. The bench marks are located along the line
of the old bridge remains at the NW point of the Key. The tide gage and staff
were located on the NE side and about 91 m (300 ft) SE of the NW point of the
key.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1974
DESIGNATION: 872 4436 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 9607
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 35.3' N ( 24.58830) LONGITUDE: 81° 38.3' W ( -81.63830)
The primary bench mark is a disk located in the vicinity of the old bridge
remains located at the NW point of the Key, 28 m (92 ft) SW of the outer edge of
mangroves, 8 m (26 ft) SSW of bench mark NO 3 1974, 0.21 m (0.7 ft) east of a
metal witness post, and 0.18 m (0.6 ft) south of a fibrous witness post. The
bench mark is 21 cm (0.7 ft) above ground, crimped to the top of a copper-clad
steel rod driven an unspecified depth to refusal, and encased in a 4-inch pipe.
NOTE: The mark is submerged at high tide.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8724436 PUBLICATION DATE: 02/05/2004
Name: BIRD KEY
FL
NOAA Chart: 11445 Latitude: 24° 35.3' N ( 24.58830)
USGS Quad: BOCA CHICA KEY Longitude: 81° 38.3' W ( -81.63830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 2 1974
DESIGNATION: 872 4436 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 9608
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 35.3' N ( 24.58830) LONGITUDE: 81° 38.3' W ( -81.63830)
The bench mark is a disk located in the vicinity of the old bridge remains
located at the NW point of the Key, 4 m (12 ft) SW of the outer edge of
mangroves, 0.18 m (0.6 ft) NW of a metal witness post, and 0.15 m (0.5 ft) SW of
a fibrous witness post. The bench mark is 21 cm (0.7 ft) above ground, crimped
to the top of a copper-clad steel rod driven an unspecified depth to refusal,
and encased in a 4-inch pipe. NOTE: The mark is submerged at high tide.
BENCH MARK STAMPING: NO 3 1974
DESIGNATION: 872 4436 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 9609
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 35.3' N ( 24.58830) LONGITUDE: 81° 38.3' W ( -81.63830)
The bench mark is a disk located in the vicinity of the old bridge remains
located at the NW point of the Key, 20 m (66 ft) SW of the outer edge of
mangroves, 16 m (54 ft) SW of bench mark NO 2 1974, 0.70 m (2.3 ft) west of a
witness sign nailed to a tree, and 0.27 m (0.9 ft) SSW of a witness post. The
bench mark is 21 cm (0.7 ft) above ground, crimped to the top of a copper-clad
steel rod driven an unspecified depth to refusal, and encased in a 4-inch pipe.
NOTE: The mark is submerged at high tide.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8724436 PUBLICATION DATE: 02/05/2004
Name: BIRD KEY
FL
NOAA Chart: 11445 Latitude: 24° 35.3' N ( 24.58830)
USGS Quad: BOCA CHICA KEY Longitude: 81° 38.3' W ( -81.63830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 4 1974
DESIGNATION: 872 4436 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 9610
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 35.3' N ( 24.58830) LONGITUDE: 81° 38.3' W ( -81.63830)
The bench mark is a disk located in the vicinity of the old bridge remains
located at the NW point of the Key, 36 m (119 ft) SW of the outer edge of
mangroves, 8.32 m (27.3 ft) SW of bench mark NO 1 1974, and 0.12 m (0.4 ft) east
of a witness post. The bench mark is 21 cm (0.7 ft) above ground, crimped to
the top of a copper-clad steel rod driven an unspecified depth to refusal, and
encased in a 4-inch pipe. NOTE: The mark is submerged at high tide.
BENCH MARK STAMPING: NO 5 1974
DESIGNATION: 872 4436 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 9611
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 35.3' N ( 24.58830) LONGITUDE: 81° 38.3' W ( -81.63830)
The bench mark is a disk located in the vicinity of the old bridge remains
located at the NW point of the Key, 53 m (174 ft) SW of the outer edge of
mangroves, 16.82 m (55.2 ft) SW of bench mark NO 4 1974, 0.43 m (1.4 ft) SSE of
a metal witness post, and 0.12 m (0.4 ft) WNW of a fibrous witness post. The
bench mark is 15 cm (0.5 ft) above ground level, crimped to the top of a
copper-clad steel rod driven an unspecified depth to refusal, and encased in a
4-inch pipe. NOTE: The mark is submerged at high tide.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8724436 PUBLICATION DATE: 02/05/2004
Name: BIRD KEY
FL
NOAA Chart: 11445 Latitude: 24° 35.3' N ( 24.58830)
USGS Quad: BOCA CHICA KEY Longitude: 81° 38.3' W ( -81.63830)
T I D A L D A T U M S
Tidal datums at BIRD KEY based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: April 1974 - May 1974
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8724211 BIG PINE KEY VIADUCT
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.338
MEAN HIGH WATER MHW = 0.269
MEAN SEA LEVEL MSL = 0.151
MEAN TIDE LEVEL MTL = 0.148
MEAN LOW WATER MLW = 0.028
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 1974 0.268 -0.001
NO 2 1974 0.164 -0.105
NO 3 1974 0.300 0.031
NO 4 1974 0.308 0.039
NO 5 1974 0.284 0.015
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8724436 PUBLICATION DATE: 02/05/2004
Name: BIRD KEY
FL
NOAA Chart: 11445 Latitude: 24° 35.3' N ( 24.58830)
USGS Quad: BOCA CHICA KEY Longitude: 81° 38.3' W ( -81.63830)
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.