U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8723971 PUBLICATION DATE: 05/28/2004
Name: BOOT KEY HARBOR
FL
NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330)
USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500)
To reach the tidal bench marks from the east end of the Seven Mile bridge,
proceed east on U.S. Highway 1 for 2.4 km (1.5 mi) to County Road C931 (20th
Stree Ocean), then turn right and proceed south on County Road C931 for 0.3 km
(0.2 mi) to the bridge over Boot Key Harbor. The bench marks are located along
the bridge. The tide gage and staff were located on the SE end of the bridge.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1975
DESIGNATION: 872 3971 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 6295
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0890
SETTING CLASSIFICATION: Concrete bridge sidewalk OPUS PID:
LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500)
The primary bench mark is a disk set flush in the NE corner of the concrete
bridge sidewalk, 5.12 m (16.8 ft) east of the centerline of County Road C931, 3
m (11 ft) south of the north end of the bridge, and 0.15 m (0.5 ft) above road
level.
BENCH MARK STAMPING: NO 2 1975
DESIGNATION: 872 3971 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 6296
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0889
SETTING CLASSIFICATION: Concrete pad OPUS PID:
LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500)
The bench mark is a disk set flush in a concrete pad for a bridge caution light,
26 m (85 ft) NW of bench mark NO 1 1975, 20.73 m (68.0 ft) north of the NW
corner of the bridge, and 6 m (20 ft) west of the centerline of County Road
C931.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8723971 PUBLICATION DATE: 05/28/2004
Name: BOOT KEY HARBOR
FL
NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330)
USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3971 C
DESIGNATION: 872 3971 C TIDAL FLDT
MONUMENTATION: Bench Mark disk VM#: 6297
AGENCY: Florida Department of Transportation
(FLDT) IDB PID#: AA0891
SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID:
LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500)
The bench mark is a disk set flush in the NW corner of the concrete bridge
guardrail, 23 m (75 ft) south of bench mark NO 2 1975, 11 m (35 ft) west of
bench mark NO 1 1975, 5.64 m (18.5 ft) west of the centerline of County Road
C931, 2.44 m (8.0 ft) south of the north end of the guardrail, and 1 m (3 ft)
above road level.
BENCH MARK STAMPING: 3971 D 1982
DESIGNATION: 872 3971 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 6298
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0892
SETTING CLASSIFICATION: Concrete bridge foundation OPUS PID:
LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500)
The bench mark is a disk set flush in a concrete foundation for the drawbridge,
57.45 m (188.5 ft) south of the NE corner of the bridge, 11.31 m (37.1 ft) east
of the NE corner of the bridge tender's building, and 5.55 m (18.2 ft) east of
the centerline of County Road C931.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8723971 PUBLICATION DATE: 05/28/2004
Name: BOOT KEY HARBOR
FL
NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330)
USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3971 E
DESIGNATION: 872 3971 E TIDAL FLDT
MONUMENTATION: Bench Mark disk VM#: 6299
AGENCY: Florida Department of Transportation
(FLDT) IDB PID#: AA0893
SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID:
LATITUDE: 24° 42.2' N ( 24.70330) LONGITUDE: 81° 6.3' W ( -81.10500)
The bench mark is a disk set flush in the top of the concrete guardrail located
at the SE corner of the bridge, 5.33 m (17.5 ft) east of the centerline of
County Road C931, 2.41 m (7.9 ft) north of the south end of the guardrail, 0.15
m (0.5 ft) south of the bridge abutment, and 1 m (3 ft) above road level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8723971 PUBLICATION DATE: 05/28/2004
Name: BOOT KEY HARBOR
FL
NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330)
USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500)
T I D A L D A T U M S
Tidal datums at BOOT KEY HARBOR based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: April 1975 - May 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 = 0.592
North American Vertical Datum NAVD88 = 0.565
MEAN HIGH WATER MHW = 0.522
MEAN SEA LEVEL MSL = 0.293
MEAN TIDE LEVEL MTL = 0.288
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 1 1975 8.402 7.880
NO 2 1975 7.417 6.895
3971 C 9.262 8.740
3971 D 1982 10.137 9.615
3971 E 3.980 3.458
Foot Notes:
Bench marks 3971 D 1982 and 3971 E are based on one differential leveling
connection and do not meet the quality control standards of the NOS. Therefore,
caution should be used when deriving elevations for these marks.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8723971 PUBLICATION DATE: 05/28/2004
Name: BOOT KEY HARBOR
FL
NOAA Chart: 11449 Latitude: 24° 42.2' N ( 24.70330)
USGS Quad: MARATHON Longitude: 81° 6.3' W ( -81.10500)
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.