U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8773767 PUBLICATION DATE: 05/22/2020
Name: MATAGORDA BAY ENTRANCE CHANNEL, MATAGORD
TX
NOAA Chart: 11319 Latitude: 28° 25.6' N ( 28.42690)
USGS Quad: DECROS POINT Longitude: 96° 19.8' W ( -96.33010)
To reach the tidal bench marks from the boat launch facilities at the end of
Byers Drive in Port O'Connor TX, proceed by boat east down the canal out of Port
O'Connor 9.7 km (5.0 miles) and then proceed SE in the Matagorda Ship Channel
for 4.2 km (2.6 miles). The bench marks are located on the shore to the SW and
parallel along a dirt road heading NW on Matagorda Island. The tide gauge is
located on a single pile instrumentation platform just west of the shipping
channel in the pass.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 3767 A 2016
DESIGNATION: 877 3767 A
MONUMENTATION: Metal Rod VM#: 21980
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Flange encased rod OPUS PID:
LATITUDE: 28° 25.6' N ( 28.42669) LONGITUDE: 96° 19.8' W ( -96.33083)
The bench mark is located 70.50 m (231.3 ft) NE of bench mark 877 3767 B, 4.51 m
(14.8 ft) east of the centerline of a gravel road running north to south along
the island, and 0.91 m (3.0 ft) SW of a witness post. The datum point is set is
set flush with the ground, being the top of a stainless steel rod driven 7.3 m
(24 ft) to refusal, in a sleeve depth of 0.9 m (3 ft) and encased in a 5-inch
NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8773767 PUBLICATION DATE: 05/22/2020
Name: MATAGORDA BAY ENTRANCE CHANNEL, MATAGORD
TX
NOAA Chart: 11319 Latitude: 28° 25.6' N ( 28.42690)
USGS Quad: DECROS POINT Longitude: 96° 19.8' W ( -96.33010)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3767 B 2016
DESIGNATION: 877 3767 B
MONUMENTATION: Metal Rod VM#: 21981
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Flange encased rod OPUS PID#: BBFG26
LATITUDE: 28° 25.6' N ( 28.42667) LONGITUDE: 96° 19.9' W ( -96.33156)
The bench mark is located 81.50 m (267.4 ft) south of bench mark 877 3767 C,
4.40 m (14.4 ft) NE of the centerline of the gravel road running north to south
along the island, and 3.40 m (11.2 ft) south of a witness post. The datum point
is set is set flush with the ground, being the top of a stainless steel rod
driven 19.5 m (64 ft) to refusal, in a sleeve depth of 0.9 m (3 ft) and encased
in a 5-inch NOS logo cap.
BENCH MARK STAMPING: 3767 C 2016
DESIGNATION: 877 3767 C
MONUMENTATION: Metal Rod VM#: 21982
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Flange encased rod OPUS PID:
LATITUDE: 28° 25.6' N ( 28.42722) LONGITUDE: 96° 19.9' W ( -96.33206)
The bench mark is located 78 m (255.9 ft) south of bench mark 877 3767 E, 5.50 m
(18.0 ft) east of the centerline of the gravel road running north to south on
the island, and 0.70 m (2.3 ft) SW of a witness post. The datum point is set is
set flush with the ground, being the top of a stainless steel rod driven 17.4 m
(57 ft) to refusal, in a sleeve depth of 0.9 m (3 ft) and encased in a 5-inch
NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8773767 PUBLICATION DATE: 05/22/2020
Name: MATAGORDA BAY ENTRANCE CHANNEL, MATAGORD
TX
NOAA Chart: 11319 Latitude: 28° 25.6' N ( 28.42690)
USGS Quad: DECROS POINT Longitude: 96° 19.8' W ( -96.33010)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 3767 D 2016
DESIGNATION: 877 3767 D
MONUMENTATION: Metal Rod VM#: 21983
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Flange encased rod OPUS PID#: BBGK23
LATITUDE: 28° 25.7' N ( 28.42836) LONGITUDE: 96° 20.0' W ( -96.33311)
The bench mark is 80 m (262.5 ft) NW of bench mark 877 3767 E, 75.20 m (246.7
ft) SW of the western edge of a rock jetty at the shoreline, 5.80 m (19.0 ft) NE
of the centerline of the gravel road running north to south on the island, and 3
m (9.8 ft) SW of a witness post. The datum point is set is set flush with the
ground, being the top of a stainless steel rod driven 19.2 m (63 ft) to refusal,
in a sleeve depth of 0.9 m (3 ft) and encased in a 5-inch NOS logo cap.
BENCH MARK STAMPING: 3767 E 2016
DESIGNATION: 877 3767 E
MONUMENTATION: Metal Rod VM#: 21984
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Flange encased rod OPUS PID:
LATITUDE: 28° 25.7' N ( 28.42778) LONGITUDE: 96° 20.0' W ( -96.33264)
The bench mark is located 78.0 m (255.9 ft) south of bench mark 877 3767 C, 5.50
m (18.0 ft) NE of the centerline of the gravel road running north to south on
the island, and 3.30 m (10.8 ft) SW of a witness post. The datum point is set is
set flush with the ground, being the top of a stainless steel rod driven 17.7 m
(58 ft) to refusal, in a sleeve depth of 0.9 m (3 ft) and encased in a 5-inch
NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8773767 PUBLICATION DATE: 05/22/2020
Name: MATAGORDA BAY ENTRANCE CHANNEL, MATAGORD
TX
NOAA Chart: 11319 Latitude: 28° 25.6' N ( 28.42690)
USGS Quad: DECROS POINT Longitude: 96° 19.8' W ( -96.33010)
T I D A L D A T U M S
Tidal datums at MATAGORDA BAY ENTRANCE CHANNEL, MATAGORD based on:
LENGTH OF SERIES: 3 YEARS
TIME PERIOD: 7/16-6/17, 9/17-8/19
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8775870 BOB HALL PIER, CORPUS CHRISTI
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (10/08/2017) = 1.032
MEAN HIGHER HIGH WATER MHHW = 0.377
MEAN HIGH WATER MHW = 0.369
MEAN SEA LEVEL MSL = 0.225
MEAN TIDE LEVEL MTL = 0.202
North American Vertical Datum NAVD88 = 0.114
MEAN LOW WATER MLW = 0.034
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (01/20/2019) = -0.513
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
3767 A 2016 2.264 1.895
3767 B 2016 2.068 1.699
3767 C 2016 2.198 1.829
3767 D 2016 2.110 1.741
3767 E 2016 2.138 1.769
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8773767 PUBLICATION DATE: 05/22/2020
Name: MATAGORDA BAY ENTRANCE CHANNEL, MATAGORD
TX
NOAA Chart: 11319 Latitude: 28° 25.6' N ( 28.42690)
USGS Quad: DECROS POINT Longitude: 96° 19.8' W ( -96.33010)
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.