U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8746943 PUBLICATION DATE: 02/26/2004
Name: HENDERSON AVENUE BRIDGE, BAYOU PORTAGE
MS
NOAA Chart: 11371 Latitude: 30° 20.5' N ( 30.34170)
USGS Quad: BAY ST. LOUIS Longitude: 89° 15.9' W ( -89.26500)
To reach the tidal bench marks from the intersection of Henderson Avenue and
U.S. Highway 90 in Pass Christian, proceed north on Henderson Avenue for 3.4 km
(2.1 mi) to a shell driveway on the west (left) side of the road just south of
the bridge over Bayou Portage, then turn left and proceed west on the shell
driveway for 0.2 km (0.1 mi) to the Hotz residence. The bench marks are located
along Henderson Avenue, the shell driveway, and the Hotz residence. The tide
gage and staff were located on the NW and NE corners, respectively, of the Hotzs
private pier on the south bank of Bayou Portage.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6943 B 1978
DESIGNATION: 874 6943 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 10415
AGENCY: Nation Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 30° 20.5' N ( 30.34170) LONGITUDE: 89° 15.9' W ( -89.26500)
The primary bench mark is a disk located 64 m (211 ft) SE of bench mark 6943 A
1978, 64 m (209 ft) SSE of the SE corner of the Hotz residence, 9 m (30 ft) SW
of the centerline of the Hotz driveway, and 3.23 m (10.6 ft) west of a power
pole. The bench mark is set 0.15 m (0.5 ft) below ground level, crimped to the
top of a steel rod driven 14.6 m (48 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 2 of 6
Station ID: 8746943 PUBLICATION DATE: 02/26/2004
Name: HENDERSON AVENUE BRIDGE, BAYOU PORTAGE
MS
NOAA Chart: 11371 Latitude: 30° 20.5' N ( 30.34170)
USGS Quad: BAY ST. LOUIS Longitude: 89° 15.9' W ( -89.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6943 A 1978
DESIGNATION: 874 6943 A TIDAL
MONUMENTATION: Tidal Station disk VM#: 10414
AGENCY: Nation Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Old foundation OPUS PID:
LATITUDE: 30° 20.5' N ( 30.34170) LONGITUDE: 89° 15.9' W ( -89.26500)
The bench mark is a disk set flush on the NW corner of an old concrete
foundation, 35 m (116 ft) south of the south shore of Bayou Portage, 19.69 m
(64.6 ft) south of the NW corner of the Hotz residence, and 11.67 m (38.3 ft) SW
of the SW corner of the Hotz residence.
BENCH MARK STAMPING: 6943 C 1978
DESIGNATION: 874 6943 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 10416
AGENCY: Nation Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 30° 20.5' N ( 30.34170) LONGITUDE: 89° 15.9' W ( -89.26500)
The bench mark is a disk located along the driveway leading to the Hotz
residence, 69 m (225 ft) east of bench mark 6943 B 1978, 16.46 m (54.0 ft) east
of power pole #E-G-E-UL-LR-FT-840, 12 m (39 ft) east of a fenceline, and 5.00 m
(16.4 ft) south of the centerline of the driveway. The bench mark is set 0.18 m
(0.6 ft) below ground level, crimped to the top of a steel rod driven 14.6 m (48
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: 8746943 PUBLICATION DATE: 02/26/2004
Name: HENDERSON AVENUE BRIDGE, BAYOU PORTAGE
MS
NOAA Chart: 11371 Latitude: 30° 20.5' N ( 30.34170)
USGS Quad: BAY ST. LOUIS Longitude: 89° 15.9' W ( -89.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6943 D 1978
DESIGNATION: 874 6943 D TIDAL
MONUMENTATION: Tidal Station disk VM#: 10417
AGENCY: Nation Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 30° 20.5' N ( 30.34170) LONGITUDE: 89° 15.9' W ( -89.26500)
The bench mark is a disk located near the intersection of the Hotz driveway and
Henderson Avenue, 73 m (241 ft) east of bench mark 6943 C 1978, 22.04 m (72.3
ft) west of the centerline of Henderson Avenue, 5.49 m (18.0 ft) NNW of the NW
corner of a brick pillar, and 3.51 m (11.5 ft) NNW of the centerline of the
driveway. The bench mark is set 0.15 m (0.5 ft) below ground level, crimped to
the top of a steel rod driven 14.6 m (48 ft) to refusal, and encased in a 4-inch
PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 6943 E 1978
DESIGNATION: 874 6943 E TIDAL
MONUMENTATION: Tidal Station disk VM#: 10418
AGENCY: Nation Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Bridge abutment OPUS PID:
LATITUDE: 30° 20.5' N ( 30.34170) LONGITUDE: 89° 15.9' W ( -89.26500)
The bench mark is a disk set flush on an abutment at the SW end of the Henderson
Avenue Bridge over Bayou Portage, 177 m (580 ft) north of bench mark 6943 D
1978, 7.80 m (25.6 ft) SE of a support pole for the power line, and 4.82 m (15.8
ft) WSW of the centerline of Henderson Avenue.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8746943 PUBLICATION DATE: 02/26/2004
Name: HENDERSON AVENUE BRIDGE, BAYOU PORTAGE
MS
NOAA Chart: 11371 Latitude: 30° 20.5' N ( 30.34170)
USGS Quad: BAY ST. LOUIS Longitude: 89° 15.9' W ( -89.26500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: Z 134 1943
DESIGNATION: Z 134
MONUMENTATION: Bench Mark disk VM#: 10419
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: BH0997
SETTING CLASSIFICATION: Concrete post OPUS PID:
LATITUDE: 30° 23.1' N ( 30.38500) LONGITUDE: 89° 14.8' W ( -89.24670)
The bench mark is a disk set in a concrete post 0.15 m (0.5 ft) above ground
level, 4.26 km (2.65 mi) NW and west along a black top road from the school at
Cuevas, 0.72 km (0.45 mi) west of the junction of a road north, 56.69 m (186.0
ft) NE and across the road from telephone pole #22, 56 m (184 ft) west of the
junction of the north side ditch of the road and a small drainage ditch leading
NW from the road, 8.23 m (27.0 ft) north of the centerline of the road, 1.37 m
(4.5 ft) north of the fence line, and 0.91 m (3.0 ft) north of a white wooden
witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8746943 PUBLICATION DATE: 02/26/2004
Name: HENDERSON AVENUE BRIDGE, BAYOU PORTAGE
MS
NOAA Chart: 11371 Latitude: 30° 20.5' N ( 30.34170)
USGS Quad: BAY ST. LOUIS Longitude: 89° 15.9' W ( -89.26500)
T I D A L D A T U M S
Tidal datums at HENDERSON AVENUE BRIDGE, BAYOU PORTAGE based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: November 1978 - January 1979
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8747038 HENDERSON AVENUE BRIDGE, WOLF RIVER
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.546
MEAN HIGH WATER MHW = 0.498
MEAN SEA LEVEL MSL = 0.278
MEAN TIDE LEVEL MTL = 0.273
MEAN LOW WATER MLW = 0.048
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6943 B 1978 0.736 0.238
6943 A 1978 1.488 0.990
6943 C 1978 1.303 0.805
6943 D 1978 1.417 0.919
6943 E 1978 3.567 3.069
Z 134 1943 5.010 4.512
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8746943 PUBLICATION DATE: 02/26/2004
Name: HENDERSON AVENUE BRIDGE, BAYOU PORTAGE
MS
NOAA Chart: 11371 Latitude: 30° 20.5' N ( 30.34170)
USGS Quad: BAY ST. LOUIS Longitude: 89° 15.9' W ( -89.26500)
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.