U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
Station ID: 8729435 PUBLICATION DATE: 05/12/2004
Name: BIG HAMMOCK PT, CHOCTAWHATCHEE BAY
FL
NOAA Chart: 11388 Latitude: 30° 27.9' N ( 30.46500)
USGS Quad: CHOCTAW BEACH Longitude: 86° 21.1' W ( -86.35170)
To reach the tidal bench marks from Tri-Village Fire Department on State Highway
20 in Choctaw Beach, proceed west on State Highway 20 for 0.2 km (0.1 mi) to the
residence at Box 1102A on the south side of the highway. The bench marks are on
properties bordering State Highway 20 and adjacent to the residence. The tide
gage and staff were on the pier at the residence.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9435 A 1988
DESIGNATION: 872 9435 A
MONUMENTATION: Tidal Station disk VM#: 10116
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete step OPUS PID:
LATITUDE: 30° 27.9' N ( 30.46500) LONGITUDE: 86° 21.1' W ( -86.35170)
The primary bench mark is a disk set in the bottom concrete step on the west
side of the residence at Box 1102A, 1.04 m (3.4 ft) north of the south edge of
the step, and 0.15 m (0.5 ft) east of the west edge.
BENCH MARK STAMPING: 9435 C 1988
DESIGNATION: 872 9435 C
MONUMENTATION: Tidal Station disk VM#: 10117
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete driveway OPUS PID:
LATITUDE: 30° 27.9' N ( 30.46500) LONGITUDE: 86° 21.1' W ( -86.35170)
The bench mark is a disk set in the NW corner of the Tri-Village Fire Department
driveway, 0.15 m (0.5 ft) south of the north edge, and 0.15 m (0.5 ft) east of
the west edge.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 8729435 PUBLICATION DATE: 05/12/2004
Name: BIG HAMMOCK PT, CHOCTAWHATCHEE BAY
FL
NOAA Chart: 11388 Latitude: 30° 27.9' N ( 30.46500)
USGS Quad: CHOCTAW BEACH Longitude: 86° 21.1' W ( -86.35170)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9435 D 1988
DESIGNATION: 872 9435 D
MONUMENTATION: Tidal Station disk VM#: 10118
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete sidewalk OPUS PID:
LATITUDE: 30° 27.9' N ( 30.46500) LONGITUDE: 86° 21.1' W ( -86.35170)
The bench mark is a disk set in the east end of the concrete sidewalk in front
of Tri-Village Fire Department, 0.34 m (1.1 ft) south of the north edge, and
0.21 m (0.7 ft) west of the east edge.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
Station ID: 8729435 PUBLICATION DATE: 05/12/2004
Name: BIG HAMMOCK PT, CHOCTAWHATCHEE BAY
FL
NOAA Chart: 11388 Latitude: 30° 27.9' N ( 30.46500)
USGS Quad: CHOCTAW BEACH Longitude: 86° 21.1' W ( -86.35170)
T I D A L D A T U M S
Tidal datums at BIG HAMMOCK PT, CHOCTAWHATCHEE BAY based on:
LENGTH OF SERIES: 11 MONTHS
TIME PERIOD: May 1992 - March 1993
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8729840 PENSACOLA, PENSACOLA BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.148
MEAN HIGH WATER MHW = 0.148
MEAN TIDE LEVEL MTL = 0.075
MEAN SEA LEVEL MSL = 0.071
MEAN LOW WATER MLW = 0.001
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
9435 A 1988 4.000 3.852
9435 C 1988 5.000 4.852
9435 D 1988 5.281 5.133
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 8729435 PUBLICATION DATE: 05/12/2004
Name: BIG HAMMOCK PT, CHOCTAWHATCHEE BAY
FL
NOAA Chart: 11388 Latitude: 30° 27.9' N ( 30.46500)
USGS Quad: CHOCTAW BEACH Longitude: 86° 21.1' W ( -86.35170)
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.