U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
Station ID: 8724224 PUBLICATION DATE: 04/13/2005
Name: LITTLE TORCH KEY
FL
NOAA Chart: 11445 Latitude: 24° 39.9' N ( 24.66500)
USGS Quad: SUMMERLAND KEY Longitude: 81° 23.2' W ( -81.38670)
To reach the tidal bench marks from the post office in Big Pine, proceed west on
U.S. Highway 1 for 2.6 km (1.6 mi) to the west end of the bridge over Pine
Channel and a boat basin near the residence of Robert Ryan just SW of the
bridge. The bench marks are located on the bridge and in the vicinity of the
boat basin. The tide gage and staff were located at the east end of the
northern wooden dock of the boat basin.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 2 1974
DESIGNATION: 872 4224 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 6477
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0698
SETTING CLASSIFICATION: Concrete sidewalk OPUS PID:
LATITUDE: 24° 39.9' N ( 24.66500) LONGITUDE: 81° 23.2' W ( -81.38670)
The bench mark is a disk set in the sidewalk on the west side of a refrigerated
storage building on the north side of the boat basin, 5.09 m (16.7 ft) north of
the north wall of the boat basin, and about level with the ground.
BENCH MARK STAMPING: NO 3 1974
DESIGNATION: 872 4224 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 6478
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0700
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 24° 39.9' N ( 24.66500) LONGITUDE: 81° 23.2' W ( -81.38670)
The bench mark is a disk set in the south seawall of the boat 23.41 m (76.8 ft)
west of Bench Mark NO 5 1974, 8.41 m (27.6 ft) NW of the NW corner of the Robert
Ryan residence, 0.46 m (1.15 ft) north of the west end of the seawall, and about
level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 8724224 PUBLICATION DATE: 04/13/2005
Name: LITTLE TORCH KEY
FL
NOAA Chart: 11445 Latitude: 24° 39.9' N ( 24.66500)
USGS Quad: SUMMERLAND KEY Longitude: 81° 23.2' W ( -81.38670)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1974
DESIGNATION: 872 4224 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 6479
AGENCY: National Ocean Survey (NOS) IDB PID#: AA0701
SETTING CLASSIFICATION: Concrete sea wall OPUS PID:
LATITUDE: 24° 39.9' N ( 24.66500) LONGITUDE: 81° 23.2' W ( -81.38670)
The bench mark is a disk set in the south seawall of the boat basin at the SE
corner of the bain entrance, 11.19 m (36.7 ft) NE of the NE corner of the Robert
Ryan residence, and about level with the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 8724224 PUBLICATION DATE: 04/13/2005
Name: LITTLE TORCH KEY
FL
NOAA Chart: 11445 Latitude: 24° 39.9' N ( 24.66500)
USGS Quad: SUMMERLAND KEY Longitude: 81° 23.2' W ( -81.38670)
T I D A L D A T U M S
Tidal datums at LITTLE TORCH KEY based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: December 1974 - December 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:
North American Vertical Datum NAVD88 = 0.410
MEAN HIGHER HIGH WATER MHHW = 0.386
MEAN HIGH WATER MHW = 0.315
MEAN TIDE LEVEL MTL = 0.168
MEAN SEA LEVEL MSL = 0.167
MEAN LOW WATER MLW = 0.021
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 2 1974 0.776 0.461
NO 3 1974 1.045 0.730
NO 5 1974 1.065 0.750
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 8724224 PUBLICATION DATE: 04/13/2005
Name: LITTLE TORCH KEY
FL
NOAA Chart: 11445 Latitude: 24° 39.9' N ( 24.66500)
USGS Quad: SUMMERLAND KEY Longitude: 81° 23.2' W ( -81.38670)
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.