U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8723457 PUBLICATION DATE: 11/13/2003
Name: CHRISTMAS POINT, ELLIOTT KEY
FL
NOAA Chart: 11463 Latitude: 25° 23.5' N ( 25.39170)
USGS Quad: ELLIOTT KEY Longitude: 80° 13.8' W ( -80.23000)
To reach the tidal bench marks from Ocean Reef Harbor near the north end of Key
Largo, proceed by boat NE along the east side of Key Largo and Old Rhodes Key
for 10.5 km (6.5 statute mi) to Christmas Point at the south end of Elliott Key.
The bench marks are located in an area of small mangroves surrounded by larger
mangroves just north of Christmas Point. The tide gage and staff were located
offshore of Christmas Point in Caesar Creek.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1974
DESIGNATION: 872 3457 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 5866
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 25° 23.5' N ( 25.39170) LONGITUDE: 80° 13.8' W ( -80.23000)
The primary bench mark is a disk set in a concrete monument located 61 m (200
ft) north of Christmas Point, 10 m (34 ft) SW of a large mangrove with 4 trunks,
2 m (8 ft) NW of the inside limit of large mangroves, 0.24 m (0.8 ft) SE of a
witness post, and 0.06 m (0.2 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8723457 PUBLICATION DATE: 11/13/2003
Name: CHRISTMAS POINT, ELLIOTT KEY
FL
NOAA Chart: 11463 Latitude: 25° 23.5' N ( 25.39170)
USGS Quad: ELLIOTT KEY Longitude: 80° 13.8' W ( -80.23000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 2 1974
DESIGNATION: 872 3457 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 5867
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 25° 23.5' N ( 25.39170) LONGITUDE: 80° 13.8' W ( -80.23000)
The bench mark is set in a concrete monument located 62 m (205 ft) north of
Christmas Point, 14 m (45 ft) east of the inside limit of large mangroves, 6 m
(21 ft) NW of a large mangrove with 4 trunks, 0.24 m (0.8 ft) SE of a witness
post, and 0.06 m (0.2 ft) above ground level.
BENCH MARK STAMPING: NO 3 1974
DESIGNATION: 872 3457 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 5868
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 25° 23.5' N ( 25.39170) LONGITUDE: 80° 13.8' W ( -80.23000)
The bench mark is a disk set in a concrete monument located 75 m (245 ft) NE of
Christmas Point, 13 m (44 ft) NNE of bench mark NO 1 1974, 7.19 m (23.6 ft) ENE
of bench mark NO 2 1974, 2.29 m (7.5 ft) NE of a large mangrove with 4 trunks,
0.24 m (0.8 ft) SE of a witness post, and 0.09 m (0.3 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8723457 PUBLICATION DATE: 11/13/2003
Name: CHRISTMAS POINT, ELLIOTT KEY
FL
NOAA Chart: 11463 Latitude: 25° 23.5' N ( 25.39170)
USGS Quad: ELLIOTT KEY Longitude: 80° 13.8' W ( -80.23000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1974
DESIGNATION: 872 3457 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 5869
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 25° 23.5' N ( 25.39170) LONGITUDE: 80° 13.8' W ( -80.23000)
The bench mark is a disk set in a concrete monument located 66 m (215 ft) NE of
Christmas Point, 13 m (43 ft) west of bench mark NO 4 1974, 10 m (34 ft) west of
a large mangrove with 4 trunks, 10 m (33 ft) north of the inside limit of large
mangroves, 9 m (30 ft) SW of bench mark NO 3 1974, 7.65 m (25.1 ft) NNW of bench
mark NO 1 1974, 3.78 m (12.4 ft) south of bench mark NO 2 1974, 0.24 m (0.8 ft)
SE of a witness post, and 0.06 m (0.2 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8723457 PUBLICATION DATE: 11/13/2003
Name: CHRISTMAS POINT, ELLIOTT KEY
FL
NOAA Chart: 11463 Latitude: 25° 23.5' N ( 25.39170)
USGS Quad: ELLIOTT KEY Longitude: 80° 13.8' W ( -80.23000)
T I D A L D A T U M S
Tidal datums at CHRISTMAS POINT, ELLIOTT KEY based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: July 1974 - July 1974
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8723350 RAGGED KEY #3
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.630
MEAN HIGH WATER MHW = 0.606
MEAN SEA LEVEL MSL = 0.335
MEAN TIDE LEVEL MTL = 0.328
MEAN LOW WATER MLW = 0.050
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 0.843 0.237
NO 2 1974 0.755 0.149
NO 3 1974 0.869 0.263
NO 5 1974 0.722 0.116
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8723457 PUBLICATION DATE: 11/13/2003
Name: CHRISTMAS POINT, ELLIOTT KEY
FL
NOAA Chart: 11463 Latitude: 25° 23.5' N ( 25.39170)
USGS Quad: ELLIOTT KEY Longitude: 80° 13.8' W ( -80.23000)
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.