U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8761724 PUBLICATION DATE: 02/16/2018
Name: GRAND ISLE, EAST POINT
LA
NOAA Chart: 11358 Latitude: 29° 15.8' N ( 29.26333)
USGS Quad: FORT LIVINGSTON Longitude: 89° 57.4' W ( -89.95667)
To reach the tidal bench marks from the Post Office in Grand Isle, proceed 3.9
km (2.4 mi) NE along State Highway 1, then 1.3 km (0.8 mi) NE along a paved
road, then 0.2 km (0.1 mi) NW along Semper Road leading to the U.S. Coast Guard
Station. The bench marks are located within the U.S. Coast Guard compound. The
tide gage is located next to the boat house.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 10
DESIGNATION: 10
MONUMENTATION: Survey disk VM#: 817
AGENCY: US Coast Guard (USCG) IDB PID#: AT0687
SETTING CLASSIFICATION: Concrete bulkhead OPUS PID:
LATITUDE: 29° 15.9' N ( 29.26511) LONGITUDE: 89° 57.5' W ( -89.95767)
The primary bench mark is a disk set in the top of a concrete seawall, 7.92 m
(25.98 ft) SSW of the north end of the concrete boat ramp, 6.61 m (21.69 ft) NNW
of the NW corner of the boat house, and 1.60 m (5.25 ft) SE of the east side of
the small boat ramp.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8761724 PUBLICATION DATE: 02/16/2018
Name: GRAND ISLE, EAST POINT
LA
NOAA Chart: 11358 Latitude: 29° 15.8' N ( 29.26333)
USGS Quad: FORT LIVINGSTON Longitude: 89° 57.4' W ( -89.95667)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1724 A 1980
DESIGNATION: 876 1724 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 822
AGENCY: National Ocean Survey (NOS) IDB PID#: AT0683
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 15.9' N ( 29.26439) LONGITUDE: 89° 57.4' W ( -89.95669)
The bench mark is a disk located 64.10 m (210.30 ft) NW of bench mark 1724 B
1980, 51.80 m (169.95 ft) SW of the center of Semper Road, 12.01 m (39.40 ft) SE
of the south corner of an old foundation, 13.60 m (44.62 ft) SSW of the NW
corner of a chainlink fence around 2 sewer treatment tanks and concrete pad, 3.0
m (9.8 ft) WSW of the SW corner of the fence and gate and 0.30 m (0.98 ft) south
of the property fence and near the water. The bench mark is set 0.3 m (1.0 ft)
below the ground level, crimped to a stainless rod driven 18.3 m (60.0 ft), and
encased in a 4 - inch Pvc pipe.
BENCH MARK STAMPING: 1724 B 1980
DESIGNATION: 876 1724 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 823
AGENCY: National Ocean Survey (NOS) IDB PID#: AT0682
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 15.9' N ( 29.26439) LONGITUDE: 89° 57.4' W ( -89.95600)
The bench mark is a disk located 64.40 m (211.29 ft) west of bench mark 1724 C
1980, 64.10 m (210.30 ft) SE of bench mark 1724 A 1980, 32.60 m (106.96 ft)
south of the center of Semper Road, 23.80 m (78.08 ft) east of the SE corner of
a chainlink fence around a sewer treatment tank, and 0.3 m (0.98 ft) south of
the property fence. The bench mark is set 0.30 m (0.98 ft) below the level of
the road and 30 cm below ground level, crimped to a stainless steel rod driven
19.8 m (65.0 ft) to refusal, and encased in a 4-inch Pvc pipe and concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8761724 PUBLICATION DATE: 02/16/2018
Name: GRAND ISLE, EAST POINT
LA
NOAA Chart: 11358 Latitude: 29° 15.8' N ( 29.26333)
USGS Quad: FORT LIVINGSTON Longitude: 89° 57.4' W ( -89.95667)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 11
DESIGNATION: 11
MONUMENTATION: Survey disk VM#: 828
AGENCY: US Coast Guard (USCG) IDB PID#: AT0685
SETTING CLASSIFICATION: Concrete bulkhead OPUS PID#: AT0685
LATITUDE: 29° 15.9' N ( 29.26483) LONGITUDE: 89° 57.5' W ( -89.95753)
The bench mark is a disk set on the top of a concrete bulkhead next to the small
boat house, 46.63 m (152.99 ft) west of the entrance doors to the Coast Guard
administration building, 18.50 m (60.70 ft) south of the NE corner of the
concrete bulkhead, and 7.38 m (24.21 ft) north of the NE pile of the NOAA tide
station platform.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8761724 PUBLICATION DATE: 02/16/2018
Name: GRAND ISLE, EAST POINT
LA
NOAA Chart: 11358 Latitude: 29° 15.8' N ( 29.26333)
USGS Quad: FORT LIVINGSTON Longitude: 89° 57.4' W ( -89.95667)
T I D A L D A T U M S
Tidal datums at GRAND ISLE, EAST POINT based on:
LENGTH OF SERIES: 19 YEARS
TIME PERIOD: Jan '83-Dec '01 & Jan '12-Mar '12, May '12-Dec '16
TIDAL EPOCH: 2012-2016
CONTROL TIDE STATION:
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (08/29/2012) = 1.594
MEAN HIGHER HIGH WATER MHHW = 0.323
MEAN HIGH WATER MHW = 0.321
MEAN SEA LEVEL MSL = 0.163
MEAN TIDE LEVEL MTL = 0.162
MEAN LOW WATER MLW = 0.003
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/13/1964) = -1.022
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
10 0.874 0.553
1724 A 1980 0.740 0.419
1724 B 1980 0.680 0.359
11 0.900 0.579
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8761724 PUBLICATION DATE: 02/16/2018
Name: GRAND ISLE, EAST POINT
LA
NOAA Chart: 11358 Latitude: 29° 15.8' N ( 29.26333)
USGS Quad: FORT LIVINGSTON Longitude: 89° 57.4' W ( -89.95667)
Foot Notes:
Certain geographic areas are experiencing rapid land movement due to uplift or
subsidence, which results in anomalous relative sea level trends compared to
most other coastal regions in the United States
(http://tidesandcurrents.noaa.gov/sltrends/index.shtml). In these areas, NOAA
has adopted a modified procedure for computing accepted tidal datums for the
National Water Level Observation Network (NWLON). The long-term control stations
in these areas have tidal datums reviewed approximately every 5 years, and if
they meet the criteria for an update, the 5-year period used for the modified
procedure will be listed in the Time Period section for the datums. The adoption
of this procedure was necessary to ensure that these tidal datums accurately
represent the existing stand of sea level relative to the land. A detailed
report explaining this modified procedure can be found in the publications
section of the CO-OPS Tides & Currents website at
http://tidesandcurrents.noaa.gov/pub.html.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8761724 PUBLICATION DATE: 02/16/2018
Name: GRAND ISLE, EAST POINT
LA
NOAA Chart: 11358 Latitude: 29° 15.8' N ( 29.26333)
USGS Quad: FORT LIVINGSTON Longitude: 89° 57.4' W ( -89.95667)
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.