U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8724273 PUBLICATION DATE: 03/22/2005
Name: WATER KEYS SOUTH END
FL
NOAA Chart: 11448 Latitude: 24° 44.8' N ( 24.74670)
USGS Quad: SUMMERLAND KEY Longitude: 81° 27.0' W ( -81.45000)
To reach the tidal bench marks from the highway bridge over Bogie Channel
between Big Pine Key and No Name Key, proceed by boat NW on Bogie Channel and
the marked channel around the north side of Howe Key for 14 km (10 nm) to the SE
end of the largest island of the Water Keys group. The bench marks are located
on the SE end of the island. The tide gage and staff were located offshore near
Daymarker 50.
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 5
Station ID: 8724273 PUBLICATION DATE: 03/22/2005
Name: WATER KEYS SOUTH END
FL
NOAA Chart: 11448 Latitude: 24° 44.8' N ( 24.74670)
USGS Quad: SUMMERLAND KEY Longitude: 81° 27.0' W ( -81.45000)
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: WATER KEY RM 1 1934-35
DESIGNATION: WATER KEY RM 1
ALIAS: 1
MONUMENTATION: Reference Mark disk VM#: 6888
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AE4411
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 44.8' N ( 24.74670) LONGITUDE: 81° 27.0' W ( -81.45000)
The primary bench mark is a disk set in a 0.21 m (0.7 ft) square concrete
monument, 31.61 m (103.7 ft) SE of bench mark 4273 D 1984, 23 m (75 ft) west of
bench mark WATER KEY 1934-35, 1 m (2 ft) SE of a witness post, and 0.21 m (0.7
ft) above ground level.
BENCH MARK STAMPING: WATER KEY 1934-35
DESIGNATION: WATER KEY
ALIAS: 3
MONUMENTATION: Triangulation Station disk VM#: 6887
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA1581
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 45.0' N ( 24.75000) LONGITUDE: 81° 26.8' W ( -81.44670)
The bench mark is a disk set in a 0.21 m (0.7 ft) square concrete monument
located in a high grassy clearing at the SE end of the island, 120 m (394 ft)
NNW of the outer mangroves SSE of the station, 69 m (226 ft) west of the outer
mangroves to the east, 38 m (125 ft) west of the inner edge of the mangroves to
the east, 0.49 m (1.6 ft) west of a witness post, and 0.21 m (0.7 ft) above
ground level.
BENCH MARK STAMPING: WATER KEY RM 2 1934-35
DESIGNATION: WATER KEY RM 2
ALIAS: 2
MONUMENTATION: Reference Mark disk VM#: 6889
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AE4412
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 44.8' N ( 24.74670) LONGITUDE: 81° 27.0' W ( -81.45000)
The bench mark is a disk set in a 0.21 m (0.7 ft) square concrete monument,
29.93 m (98.2 ft) west of bench mark 4273 F 1984, 25 m (83 ft) WNW of bench mark
WATER KEY 1934-35, 0.46 m (1.5 ft) SW of a witness post, and 0.15 m (0.5 ft)
above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8724273 PUBLICATION DATE: 03/22/2005
Name: WATER KEYS SOUTH END
FL
NOAA Chart: 11448 Latitude: 24° 44.8' N ( 24.74670)
USGS Quad: SUMMERLAND KEY Longitude: 81° 27.0' W ( -81.45000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4273 D 1984
DESIGNATION: 872 4273 D
MONUMENTATION: Tidal Station disk VM#: 6890
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 24° 44.8' N ( 24.74670) LONGITUDE: 81° 27.0' W ( -81.45000)
The bench mark is a disk set in a rock outcrop located in a clearing on the SW
side of the SE end of the island, 36 m (119 ft) WNW of bench mark WATER KEY
1934-35, 31.61 m (103.7 ft) NW of bench mark WATER KEY RM 1 1934-35, 15 m (50
ft) SW of bench mark WATER KEY RM 2 1934-35, 0.76 m (2.5 ft) east of a witness
post, and 0.06 m (0.2 ft) above ground level.
BENCH MARK STAMPING: 4273 F 1984
DESIGNATION: 872 4273 F
MONUMENTATION: Tidal Station disk VM#: 6891
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 24° 44.8' N ( 24.74670) LONGITUDE: 81° 27.0' W ( -81.45000)
The bench mark is a disk located on the SE end of the island, 47.03 m (154.3 ft)
ENE of bench mark 4273 D 1984, 29.93 m (98.2 ft) east of bench mark WATER KEY RM
2 1934-35, 19 m (61 ft) NNE of bench mark WATER KEY 1934-35, and 0.49 m (1.6 ft)
SW of a witness post. The bench mark is set 0.15 m (0.5 ft) below ground level,
crimped to the top of a stainless steel rod driven 3.7 m (12 ft), and encased in
a PVC pipe which projects 0.49 m (1.6 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8724273 PUBLICATION DATE: 03/22/2005
Name: WATER KEYS SOUTH END
FL
NOAA Chart: 11448 Latitude: 24° 44.8' N ( 24.74670)
USGS Quad: SUMMERLAND KEY Longitude: 81° 27.0' W ( -81.45000)
T I D A L D A T U M S
Tidal datums at WATER KEYS SOUTH END based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: November 1973 - February 1974
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 = 0.781
MEAN HIGH WATER MHW = 0.701
MEAN TIDE LEVEL MTL = 0.387
MEAN SEA LEVEL MSL = 0.362
MEAN LOW WATER MLW = 0.072
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
WATER KEY RM 1 1934-35 0.968 0.267
WATER KEY 1934-35 1.065 0.364
WATER KEY RM 2 1934-35 1.136 0.435
4273 D 1984 0.814 0.113
4273 F 1984 0.801 0.100
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8724273 PUBLICATION DATE: 03/22/2005
Name: WATER KEYS SOUTH END
FL
NOAA Chart: 11448 Latitude: 24° 44.8' N ( 24.74670)
USGS Quad: SUMMERLAND KEY Longitude: 81° 27.0' W ( -81.45000)
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.