U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 03/19/1986
Station ID: 8761529 SUPERCEDED DATE: 04/21/2003
Name: MARTELLO CASTLE, LAKE BORGNE
LOUISIANA
NOAA Chart: 11369 Latitude: 29° 56.7' N
USGS Quad: MARTELLO CASTLE Longitude: 89° 50.1' W
To reach the tidal bench marks from the boat landing facilities at the SW end of
the Violet Canal in Violet, on State Route 46, proceed by boat NE on the Violet
Canal and Bayou Dupree for 5.1 miles (8.2 km) to the Bayou Dupree control
structure, continue past the structure and on into the Mississippi River-Gulf
Outlet Canal, then NW on the Gulf Outlet Canal for 0.5 mile (0.8 km) to a
channel (Bayou Dupree) on the right leading to Lake Borgne, then NE for 0.2 mile
(0.3 km) to Martello Castle. The bench marks are on the castle foundation and
in the marsh south of the castle. The tide gage and staff were located on the
small pier in front of the entrance to the castle.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1529A 1983
MONUMENTATION: Survey Disk VM#: 7177
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is in the marsh approximately 800 feet (244 m) south of Martello
Castle, 225 feet (69 m) ENE of Bench Mark 1529B 1983, 85 feet (26 m) south of
the south shoreline of Bayou Dupree, and 3 feet (1 m) NW of a fiberglass witness
post. The bench mark is 0.4 foot (0.1 m) above ground level, crimped to the top
of a stainless steel rod driven 76 feet (23 m) to substantial resistance, and
encased in a 4-inch PVC pipe.
BENCH MARK STAMPING: 1529B 1983
MONUMENTATION: Survey Disk VM#: 7178
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 225 feet (69 m) WSW of Bench Mark 1529A 1983, 225 feet (69 m)
ENE of Bench Mark 1529C 1983, 80 feet (24 m) south of the south shoreline of
Bayou Dupree, and 0.7 foot (0.2 m) north of a fiberglass witness post. The
bench mark is 0.4 foot (0.1 m) above ground level, crimped to the top of a
stainless steel rod driven 76 feet (23 m) to substantial resistance, 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
PUBLICATION DATE: 03/19/1986
Station ID: 8761529 SUPERCEDED DATE: 04/21/2003
Name: MARTELLO CASTLE, LAKE BORGNE
LOUISIANA
NOAA Chart: 11369 Latitude: 29° 56.7' N
USGS Quad: MARTELLO CASTLE Longitude: 89° 50.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1529C 1983
MONUMENTATION: Survey Disk VM#: 7179
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 226 feet (69 m) NNE of Bench Mark 1529D 1983, 225 feet (69 m)
WSW of Bench Mark 1529B 1983, 49 feet (15 m) south of the south shoreline of
Bayou Dupree, and 1 foot (0.3 m) NNW of a fiberglass witness post. The bench
mark is 0.4 foot (0.1 m) above ground level, crimped to the top of a stainless
steel rod driven 76 feet (23 m) to substantial resistance, and encased in a
4-inch PVC pipe.
BENCH MARK STAMPING: 1529D 1983
MONUMENTATION: Survey Disk VM#: 7180
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 226 feet (69 m) SSW of Bench Mark 1529C 1983, 82 feet (25 m)
SE of the intersection of the Gulf Outlet and Bayou Dupree, 50 feet (15 m) NE of
the east shoreline of the Gulf Outlet, and 1.5 feet (0.5 m) ESE of a fiberglass
witness post. The bench mark is 0.4 foot (0.1 m) above ground level, crimped to
the top of a stainless steel rod driven 76 feet (23 m) to substantial
resistance, 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
PUBLICATION DATE: 03/19/1986
Station ID: 8761529 SUPERCEDED DATE: 04/21/2003
Name: MARTELLO CASTLE, LAKE BORGNE
LOUISIANA
NOAA Chart: 11369 Latitude: 29° 56.7' N
USGS Quad: MARTELLO CASTLE Longitude: 89° 50.1' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: CASTLE 1 1973
MONUMENTATION: Survey Disk VM#: 7181
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Walkway
The bench mark is set flush on the SE edge of a concrete walkway surrounding
Martello Castle, 4.2 feet (1.3 m) NE of the south corner of the castle, 4 feet
(1 m) NNW of the edge of the walkway, and 0.5 foot (0.2 m) SE of the SE wall of
the structure.
BENCH MARK STAMPING: CASTLE 2 1973
MONUMENTATION: Survey Disk VM#: 7182
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Walkway
The bench mark is set flush in the concrete walkway on the NE side of Martello
Castle, 15 feet (5 m) NE of the NE wall of the structure, and 0.5 foot (0.2 m)
SW of the edge of the walkway.
BENCH MARK STAMPING: CASTLE 3 1973
MONUMENTATION: Survey Disk VM#: 7183
AGENCY: PID:
SETTING CLASSIFICATION: Concrete Walkway
The bench mark is set flush in the concrete walkway on the west side of Martello
Castle, 23.5 feet (7.2 m) WNW of the SW corner of the castle, 2 feet (0.6 m) SSW
of the north edge of a concrete platform, and 2 feet (0.6 m) SE of the NW edge
of the platform.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 03/19/1986
Station ID: 8761529 SUPERCEDED DATE: 04/21/2003
Name: MARTELLO CASTLE, LAKE BORGNE
LOUISIANA
NOAA Chart: 11369 Latitude: 29° 56.7' N
USGS Quad: MARTELLO CASTLE Longitude: 89° 50.1' W
T I D A L D A T U M S
Tidal datums at MARTELLO CASTLE, LAKE BORGNE based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: JULY-DECEMBER 1983
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8747437 BAY WAVELAND YACHT CLUB, MS
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (10/11/1983) = 3.48
MEAN HIGHER HIGH WATER MHHW = 1.46
MEAN HIGH WATER MHW = 1.41
MEAN TIDE LEVEL MTL = 0.76
MEAN LOW WATER MLW = 0.10
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (07/26/1983) = -1.05
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
1529A 1983 2.10 0.69
1529B 1983 2.03 0.62
1529C 1983 2.06 0.65
1529D 1983 2.49 1.08
CASTLE 1 1973 3.08 1.67
CASTLE 2 1973 2.48 1.07
CASTLE 3 1973 1.86 0.45
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 03/19/1986
Station ID: 8761529 SUPERCEDED DATE: 04/21/2003
Name: MARTELLO CASTLE, LAKE BORGNE
LOUISIANA
NOAA Chart: 11369 Latitude: 29° 56.7' N
USGS Quad: MARTELLO CASTLE Longitude: 89° 50.1' 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.