U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8760742 PUBLICATION DATE: 05/06/2003
Name: COMFORT ISLAND
LA
NOAA Chart: 11363 Latitude: 29° 49.4' N ( 29.82330)
USGS Quad: MORGAN HARBOR Longitude: 89° 16.2' W ( -89.27000)
To reach the tidal bench marks from the intersection of Interstate Highway 10
and State Road 47, proceed south on State Road 47 for 14 km (9 mi), then SE on
State Road 39 for 13 km (8 mi), then east on State Road 46 for 32 km (20 mi) to
the village of Hopedale, then proceed by boat along Bayou A Loutre for 29 km (18
mi) to Treasure Pass, which leads into Christmas Camp Lake, and then continue
east across Christmas Camp Lake to the Atlantic Richfield pumping platform at
Comfort Island. The bench marks are on small islands east of the pumping
platform. The tide station was on the east side of the most southerly of the
three structures at the facility.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0742 A 1980
DESIGNATION: 876 0742 A
MONUMENTATION: Tidal Station disk VM#: 7100
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 49.4' N ( 29.82330) LONGITUDE: 89° 16.2' W ( -89.27000)
The primary bench mark is a disk located about 732 m (2400 ft) SE of the pumping
platform on a small island, 127 m (417 ft) east of the west end of the island,
18 m (58 ft) west of the east end of the island, 4 m (14 ft) north of the
shoreline of a dredged canal, and 3 m (10 ft) south of the shoreline of a bay.
The bench mark is set 0.3 m (1 ft) above ground level, crimped to the top of a
stainless steel rod driven 16.8 m (55 ft) to refusal, and encased in a 4- inch
PVC pipe.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8760742 PUBLICATION DATE: 05/06/2003
Name: COMFORT ISLAND
LA
NOAA Chart: 11363 Latitude: 29° 49.4' N ( 29.82330)
USGS Quad: MORGAN HARBOR Longitude: 89° 16.2' W ( -89.27000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0742 B 1980
DESIGNATION: 876 0742 B
MONUMENTATION: Tidal Station disk VM#: 7101
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 49.4' N ( 29.82330) LONGITUDE: 89° 16.2' W ( -89.27000)
The bench mark is a disk located on a small island east of the island on which
bench mark 0742 A 1980 is located, 77 m (252 ft) west of the east end of the
island, 5 m (16 ft) south of the shoreline of a bay, and 4 m (12 ft) north of
the shoreline of a dredged canal. The bench mark is set 0.3 m (1 ft) above
ground level, crimped to the top of a stainless steel rod driven 16.8 m (55 ft)
to refusal, and encased in a 4-inch PVC pipe.
BENCH MARK STAMPING: 0742 C 1980
DESIGNATION: 876 0742 C
MONUMENTATION: Tidal Station disk VM#: 7102
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 49.4' N ( 29.82330) LONGITUDE: 89° 16.2' W ( -89.27000)
The bench mark is a disk located on a small island SE of the island on which
bench mark 0742 A 1980 is located, 122 m (400 ft) east of well #6, and 11 m (37
ft) north of the south shoreline. The bench mark is set 0.1 m (0.3 ft) above
ground level, crimped to the top of a steel rod driven 16.8 m (55 ft) to
refusal, and encased in a 4-inch PVC pipe.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8760742 PUBLICATION DATE: 05/06/2003
Name: COMFORT ISLAND
LA
NOAA Chart: 11363 Latitude: 29° 49.4' N ( 29.82330)
USGS Quad: MORGAN HARBOR Longitude: 89° 16.2' W ( -89.27000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0742 D 1980
DESIGNATION: 876 0742 D
MONUMENTATION: Tidal Station disk VM#: 7103
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 49.4' N ( 29.82330) LONGITUDE: 89° 16.2' W ( -89.27000)
The bench mark is a disk located 62 m (205 ft) east of bench mark 0742 C 1980, 4
m (13 ft) north of an open bay, and 3 m (11 ft) south of an old dredging canal.
The bench mark is set 0.3 m (1 ft) above ground level, crimped to the top of a
stainless steel rod driven 16.8 m (55 ft) to refusal, and encased in a 4-inch
PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 0742 E 1980
DESIGNATION: 876 0742 E
MONUMENTATION: Tidal Station disk VM#: 7104
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 49.4' N ( 29.82330) LONGITUDE: 89° 16.2' W ( -89.27000)
The bench mark is a disk located 67 m (220 ft) east of bench mark 0742 D 1980,
12 m (40 ft) north of an open bay, and 6 m (20 ft) south of an old dredged
canal. The bench mark is set 0.3 m (1 ft) above ground level, crimped to the
top of a stainless steel rod driven 16.8 m (55 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 4 of 5
Station ID: 8760742 PUBLICATION DATE: 05/06/2003
Name: COMFORT ISLAND
LA
NOAA Chart: 11363 Latitude: 29° 49.4' N ( 29.82330)
USGS Quad: MORGAN HARBOR Longitude: 89° 16.2' W ( -89.27000)
T I D A L D A T U M S
Tidal datums at COMFORT ISLAND based on:
LENGTH OF SERIES: 10 MONTHS
TIME PERIOD: March 1981 - December 1981
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8747437 BAY WAVELAND YC, BAY ST. LOUIS
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.478
MEAN HIGH WATER MHW = 0.465
MEAN SEA LEVEL MSL = 0.249
MEAN TIDE LEVEL MTL = 0.244
MEAN LOW WATER MLW = 0.022
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
0742 A 1980 0.719 0.254
0742 B 1980 0.775 0.310
0742 C 1980 1.089 0.624
0742 D 1980 1.001 0.536
0742 E 1980 0.879 0.414
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8760742 PUBLICATION DATE: 05/06/2003
Name: COMFORT ISLAND
LA
NOAA Chart: 11363 Latitude: 29° 49.4' N ( 29.82330)
USGS Quad: MORGAN HARBOR Longitude: 89° 16.2' W ( -89.27000)
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.