U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 07/24/1984
Station ID: 8729333 SUPERCEDED DATE: 04/21/2003
Name: LA GRANGE BAYOU, CHOCTAWHATCHEE BAY
FLORIDA
NOAA Chart: 11388 Latitude: 30° 28.1' N
USGS Quad: FREEPORT Longitude: 86° 8.3' W
To reach the tidal bench marks from the intersection of Florida Highway 20 and
U.S. Highway 331 in Freeport, proceed south on U.S. Highway 331, 1.7 miles (2.8
km) to its intersection with La Grange Road, proceed west on La Grange Road 0.22
mile (0.35 km) to its intersection with a dirt drive leading west and NW.
Follow this drive 0.17 miles (0.27 km) to the driveway of a two story private
residence (The Davis Residence), on the south shore of La Grange Bayou. The
Bench Marks are located on both sides of the dirt drive. The tide gage and
staff were located on a wood dock behind the Davis Residence.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9333 D 1977
MONUMENTATION: Survey Disk VM#: 10092
AGENCY: PID#: BG3663
SETTING CLASSIFICATION: Concrete Post
The bench mark is set flush in the top of a concrete post 4.1 feet (1.2 m) deep,
190 feet (58 m) west of Bench Mark 9333 B 1977, 163.7 feet (49.9 m) SW of the
driveway at the private residence, 15.3 feet (4.7 m) NNW of the centerline of
the dirt drive leading NW along the shore of La Grange Bayou and 14.4 feet (4.4
m) SSE of a power pole with a witness sign. The bench mark is level with the
ground.
BENCH MARK STAMPING: 9333 A 1977
MONUMENTATION: Survey Disk VM#: 10089
AGENCY: PID#: BG3664
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set flush in the concrete foundation of the two story house
(The Davis Residence), under the wooden stairs leading to the 2nd story of the
house, 251 feet (77 m) north of Bench Mark 9333 B 1977, 70 feet (21 m) north of
the centerline of the concrete driveway leading to the carport of the residence
and 35.8 feet (10.9 m) SE ofthe west corner of the residence.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 07/24/1984
Station ID: 8729333 SUPERCEDED DATE: 04/21/2003
Name: LA GRANGE BAYOU, CHOCTAWHATCHEE BAY
FLORIDA
NOAA Chart: 11388 Latitude: 30° 28.1' N
USGS Quad: FREEPORT Longitude: 86° 8.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9333 B 1977
MONUMENTATION: Survey Disk VM#: 10090
AGENCY: PID:
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is located 12.5 feet (3.8 m) SSE of the dirt drive leading north
and NW along the shore of La Grange Bayou, 9.5 feet (2.9 m) SE of a witness post
and 5.0 feet (1.5 m) east of the centerline of the dirt drive way leading to the
private residence. The bench mark is 0.1 foot (0.1 m) below ground level,
crimped to the top of a galvanized steel rod driven 12 feet (4 m) to refusal,
encased in PVC pipe and concrete.
BENCH MARK STAMPING: 9333 C 1977
MONUMENTATION: Survey Disk VM#: 10091
AGENCY: PID:
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is located 270 feet (82 m) east of Bench Mark 9333 B 1977, 35
feet (11 m) west of a power pole, 12 feet (4 m) north of the dirt drive leading
NW to the driveway and west and across the dirt drive from a number of beehives.
The bench mark is 0.1 foot (0.1 m) below ground level, crimped to the top of a
galvanized steel rod driven 16 feet (5 m) to refusal, encased in PVC pipe and
concrete.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 07/24/1984
Station ID: 8729333 SUPERCEDED DATE: 04/21/2003
Name: LA GRANGE BAYOU, CHOCTAWHATCHEE BAY
FLORIDA
NOAA Chart: 11388 Latitude: 30° 28.1' N
USGS Quad: FREEPORT Longitude: 86° 8.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9333 E 1977
MONUMENTATION: Survey Disk VM#: 10093
AGENCY: PID#: BG3662
SETTING CLASSIFICATION: Concrete Post
The bench mark is set flush in a concrete post 4.2 feet (1.3 m) deep, 304 feet
(93 m) west of Bench Mark 9333 D 1977, 200 feet(61 m) WSW of the driveway
leading to a private residence, 19.5 feet (5.9 m) SE of the centerline of the
dirt drive alongside the south shore of La Grange Bayou and 7.6 feet (2.3 m) SW
of a power pole with a witness sign. The bench mark is 0.2 feet (0.1 m) below
ground level. NOTE: The stamping of the bench mark has an 8 stamped over the
first 3 of the designation number.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 07/24/1984
Station ID: 8729333 SUPERCEDED DATE: 04/21/2003
Name: LA GRANGE BAYOU, CHOCTAWHATCHEE BAY
FLORIDA
NOAA Chart: 11388 Latitude: 30° 28.1' N
USGS Quad: FREEPORT Longitude: 86° 8.3' W
T I D A L D A T U M S
Tidal datums at LA GRANGE BAYOU, CHOCTAWHATCHEE BAY based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: AUGUST-NOVEMBER 1977
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8729840 PENSACOLA
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (09/07/1977) = 1.94
MEAN HIGHER HIGH WATER MHHW = 0.44
MEAN HIGH WATER MHW = 0.43
MEAN TIDE LEVEL MTL = 0.23
MEAN LOW WATER MLW = 0.03
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/11/1977) = -0.81
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
9333 D 1977 9.79 9.36
9333 A 1977 4.43 4.00
9333 B 1977 9.63 9.20
9333 C 1977 6.63 6.20
9333 E 1977 8.73 8.30
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 07/24/1984
Station ID: 8729333 SUPERCEDED DATE: 04/21/2003
Name: LA GRANGE BAYOU, CHOCTAWHATCHEE BAY
FLORIDA
NOAA Chart: 11388 Latitude: 30° 28.1' N
USGS Quad: FREEPORT Longitude: 86° 8.3' W
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 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.