U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
To reach the tidal bench marks from the post office in Marathon, proceed SW on
U.S. Highway 1 for 4.7 km (2.9 mi) to the east end of Seven Mile Bridge over
Knight Key Channel. The bench marks are located on the east end of the bridge.
The tide gage and staff were located on the NE bridge wingwall.
T I D A L B E N C H M A R K S
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: Y 69 RESET 1936
DESIGNATION: Y 69 RESET
MONUMENTATION: Bench Mark disk VM#: 6306
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0297
SETTING CLASSIFICATION: Concrete bridge wing wall OPUS PID:
LATITUDE: 24° 42.4' N ( 24.70670) LONGITUDE: 81° 7.5' W ( -81.12500)
The primary bench mark is a disk set flush in the NE concrete bridge wingwall, 4
m (13 ft) north of the centerline of U.S. Highway 1, and 1 m (2 ft) below
highway level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: KNIGHT NO 2 1935
DESIGNATION: KNIGHT RM 2
MONUMENTATION: Reference Mark disk VM#: 6304
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0300
SETTING CLASSIFICATION: Concrete bridge wing wall OPUS PID:
LATITUDE: 24° 42.4' N ( 24.70670) LONGITUDE: 81° 7.5' W ( -81.12500)
The bench mark is a disk set flush in the SE concrete bridge wingwall, 7 m (23
ft) south of the centerline of U.S. Highway 1, 3.47 m (11.4 ft) SSW of bench
mark KNIGHT 2 1936, and 1 m (3 ft) below highway level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: KNIGHT 2 1936
DESIGNATION: KNIGHT 2
MONUMENTATION: Triangulation Station disk VM#: 6305
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA0299
SETTING CLASSIFICATION: Concrete bridge wing wall OPUS PID:
LATITUDE: 24° 42.4' N ( 24.70670) LONGITUDE: 81° 7.5' W ( -81.12500)
The bench mark is a disk set flush in the SE concrete bridge wingwall, 3.81 m
(12.5 ft) south of the centerline of U.S. Highway 1, and 1 m (2 ft) below
highway level.
BENCH MARK STAMPING: 4008 E 1982
DESIGNATION: 872 4008 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 6307
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0921
SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID:
LATITUDE: 24° 42.4' N ( 24.70670) LONGITUDE: 81° 7.5' W ( -81.12500)
The bench mark is a disk set flush in the base of the SE concrete bridge
guardrail, 5.67 m (18.6 ft) south of the centerline of U.S. Highway 1, 1.60 m
(5.2 ft) east of the bridge abutment, and 0.61 m (2.0 ft) west of the east end
of the guardrai.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4008 F 1982
DESIGNATION: 872 4008 F TIDAL
MONUMENTATION: Tidal Station disk VM#: 6308
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0920
SETTING CLASSIFICATION: Concrete bridge head wall OPUS PID:
LATITUDE: 24° 42.4' N ( 24.70670) LONGITUDE: 81° 7.5' W ( -81.12500)
The bench mark is a disk set flush in the NE concrete bridge headwall, 6.34 m
(20.8 ft) north of the centerline of U.S. Highway 1, 5.09 m (16.7 ft) west of
the NE corner of a concrete rail, 3 m (10 ft) below the top of a concrete rail,
and 2 m (7 ft) below highway level.
BENCH MARK STAMPING: 4008 G 1982
DESIGNATION: 872 4008 G TIDAL FLDT
MONUMENTATION: Bench Mark disk VM#: 6309
AGENCY: Florida Department of Transportation
(FLDT) IDB PID#: AA0922
SETTING CLASSIFICATION: Concrete bridge guardrail OPUS PID:
LATITUDE: 24° 42.4' N ( 24.70670) LONGITUDE: 81° 7.5' W ( -81.12500)
The bench mark is a disk set flush in the top of the NE concrete bridge
guardrail, 6.00 m (19.7 ft) north of the centerline of U.S. Highway 1, 2.10 m
(6.9 ft) west of the east end of the guardrail, 0.15 m (0.5 ft) east of the
bridge abutment, and 1 m (3 ft) below highway level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
T I D A L D A T U M S
Tidal datums at KNIGHT KEY CHANNEL based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: March 1975 - March 1975
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8724580 KEY WEST
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
North American Vertical Datum NAVD88 = 0.449
MEAN HIGHER HIGH WATER MHHW = 0.322
MEAN HIGH WATER MHW = 0.250
MEAN SEA LEVEL MSL = 0.145
MEAN TIDE LEVEL MTL = 0.141
MEAN LOW WATER MLW = 0.032
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
Y 69 RESET 1936 8.560 8.310
KNIGHT NO 2 1935 7.891 7.641
KNIGHT 2 1936 8.543 8.293
4008 E 1982 8.750 8.500
4008 F 1982 6.547 6.297
4008 G 1982 9.610 9.360
Foot Notes:
Bench marks 4008 E 1982, 4008 F 1982, and 4008 G 1982 is 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 7 of 7
Station ID: 8724008 PUBLICATION DATE: 05/12/2004
Name: KNIGHT KEY CHANNEL
FL
NOAA Chart: 11449 Latitude: 24° 42.4' N ( 24.70670)
USGS Quad: MARATHON Longitude: 81° 7.5' W ( -81.12500)
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.