U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
Station ID: 8729333 PUBLICATION DATE: 06/28/2004
Name: LA GRANGE BAYOU
FL
NOAA Chart: 11388 Latitude: 30° 28.1' N ( 30.46830)
USGS Quad: FREEPORT Longitude: 86° 8.3' W ( -86.13830)
To reach the tidal bench marks from the east junction of State Highway 20 and
U.S. Highway 331 in Freeport, proceed south on U.S. Highway 331 for 2.8 km (1.7
mi) to its intersection with La Grange Road, then west on La Grange Road for 0.3
km (0.2 mi) to its intersection with a dirt road leading north, then north on
the dirt road for 0.08 km (0.05 mi) to Holley Point Road, then west on Holley
Point Road for 0.40 km (0.25 mi) to a two-story house (Davis residence) on the
south shore of La Grange Bayou. The bench marks are along Holley Point Road and
U.S. Highway 331. The tide gage and staff were located on a wood dock at 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
DESIGNATION: 872 9333 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 10092
AGENCY: National Ocean Survey (NOS) IDB PID#: BG3663
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 30° 28.1' N ( 30.46830) LONGITUDE: 86° 8.3' W ( -86.13830)
The primary bench mark is a disk set in the top of a concrete monument, 49.90 m
(163.7 ft) SW of the driveway to the Davis residence, 4.66 m (15.3 ft) NNW of
the centerline of Holley Point Road, 4.39 m (14.4 ft) SSE of a powerline pole
with a witness sign, and 31.70 m (104.0 ft) ENE of the driveway to the Andrews
residence.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
Station ID: 8729333 PUBLICATION DATE: 06/28/2004
Name: LA GRANGE BAYOU
FL
NOAA Chart: 11388 Latitude: 30° 28.1' N ( 30.46830)
USGS Quad: FREEPORT Longitude: 86° 8.3' W ( -86.13830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9333 B 1977
DESIGNATION: 872 9333 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 10090
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Galvanized steel rod OPUS PID:
LATITUDE: 30° 28.0' N ( 30.46670) LONGITUDE: 86° 8.3' W ( -86.13830)
The bench mark is a disk located 3.81 m (12.5 ft) SSE of the dirt drive leading
north and NW along the shore of La Grange Bayou, 2.90 m (9.5 ft) SE of a witness
post and 1.52 m (5.0 ft) east of the centerline of the dirt drive way leading to
the private residence. The bench mark is 0.03 m (0.1 ft) below ground level,
crimped to the top of a galvanized steel rod driven 4 m (12 ft) to refusal,
encased in PVC pipe and concrete.
BENCH MARK STAMPING: 9333 E 1977
DESIGNATION: 872 9333 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 10093
AGENCY: National Ocean Survey (NOS) IDB PID#: BG3662
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 30° 27.9' N ( 30.46500) LONGITUDE: 86° 8.4' W ( -86.14000)
The bench mark is a disk set in the top of a concrete monument, 93 m (304 ft)
west of bench mark 9333 D 1977, 61 m (200 ft) SW of the driveway leading to the
Andrews residence, 5.94 m (19.5 ft) NW of the centerline of Holley Point Road,
and 2.32 m (7.6 ft) SW of a powerline pole with a witness sign. 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 3 of 4
Station ID: 8729333 PUBLICATION DATE: 06/28/2004
Name: LA GRANGE BAYOU
FL
NOAA Chart: 11388 Latitude: 30° 28.1' N ( 30.46830)
USGS Quad: FREEPORT Longitude: 86° 8.3' W ( -86.13830)
T I D A L D A T U M S
Tidal datums at LA GRANGE BAYOU based on:
LENGTH OF SERIES: 4 MONTHS
TIME PERIOD: August 1977 - November 1977
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 = 0.131
MEAN HIGH WATER MHW = 0.129
MEAN TIDE LEVEL MTL = 0.067
MEAN SEA LEVEL MSL = 0.067
MEAN LOW WATER MLW = 0.004
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum NAVD88 = -0.025
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
9333 D 1977 2.940 2.811
9333 B 1977 2.893 2.764
9333 E 1977 2.618 2.489
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
Station ID: 8729333 PUBLICATION DATE: 06/28/2004
Name: LA GRANGE BAYOU
FL
NOAA Chart: 11388 Latitude: 30° 28.1' N ( 30.46830)
USGS Quad: FREEPORT Longitude: 86° 8.3' W ( -86.13830)
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.