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Datums Page Page 1 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
To reach the tidal bench marks from the the Port Mansfield water tower in town
on Texas Highway 186 (Port Mansfield Drive), proceed east on Texas Highway 186
for approximately 0.3 km (0.2 mi) to the end of the road at Laguna Madre. The
bench marks are located along Texas Highway 186 and in the harbor area. The tide
gauge is on the first fishing pier north of Texas Highway 186 inside a gated
community called Mansfield Point. Station can be accessed by boat or by calling
the local Harbor Office at 956-944-2325.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1964
DESIGNATION: 877 8490 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 3100
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID:
SETTING CLASSIFICATION: Concrete head wall OPUS PID:
LATITUDE: 26° 33.5' N ( 26.55906) LONGITUDE: 97° 25.6' W ( -97.42597)
The primary bench mark is a disk set in a concrete headwall of a small culvert
at the end of State Highway 186 (Port Mansfield Drive), 7 m (23 ft) SE of a
small cottage, 5.00 (16.4 ft) west of the seawall, 1.20 m (3.9 ft) NNW of the
south end of culvert.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: BM NO 2 1964
DESIGNATION: 877 8490 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 3101
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID:
SETTING CLASSIFICATION: Concrete head wall OPUS PID:
LATITUDE: 26° 33.4' N ( 26.55667) LONGITUDE: 97° 25.7' W ( -97.42831)
The bench mark is a disk set in the SE corner of a headwall for a small concrete
box that serves as an intake for a 14-inch concrete drain midway between a boat
ramp and a warehouse, 59.98 m (196.8 ft) SW of the SW face of the warehouse,
30.00 m (98.4 ft) NW of the seaward edge of the dock, 22.90 m (75.1 ft) north of
a light pole, and 0.21 m (0.7 ft) west of the SE corner of the concrete box.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LEGION NO 5 1939 1962
DESIGNATION: LEGION RM 5
MONUMENTATION: Reference Mark disk VM#: 3103
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AB0202
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 26° 33.5' N ( 26.55856) LONGITUDE: 97° 25.7' W ( -97.42767)
The bench mark is a disk set in the top of a 0.3 m x 0.3 m (1 ft x 1 ft)
concrete post, 16.50 m (54.1 ft) NW of the centerline of Texas State Highway 186
(Port Mansfield Drive), 6.50 m (21.3 ft) SW of the centerline of White Drive,
1.0 m (3.3 ft) NW of utility pole number 15, 0.50 m (1.6 ft) south of a metal
witness post, and flush with the ground.
BENCH MARK STAMPING: 8490 B 1978
DESIGNATION: 877 8490 B
MONUMENTATION: Bench Mark disk VM#: 3105
AGENCY: National Ocean Survey (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete retaining wall OPUS PID:
LATITUDE: 26° 33.4' N ( 26.55622) LONGITUDE: 97° 25.7' W ( -97.42883)
The bench mark is a disk located on the north side of Port Mansfield Harbor on
the west side of the public boat ramp, 15.20 m (50.00 ft) north of the east end
of the gas dock at Port Mansfield Marina, 15.00 m (50.00 ft) SE of the NE corner
of the Port Mansfield Marina Building, 11.40 m (37.40 ft) east of the SE corner
of the Marina Building, and 6.00 m (19.70 ft) south of the southern side of the
steps leading to the boat ramp.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8490 D 1990
DESIGNATION: 877 8490 D
MONUMENTATION: Tidal Station disk VM#: 3107
AGENCY: National Ocean Service (NOS) IDB PID#: DP0733
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: DP0733
LATITUDE: 26° 33.4' N ( 26.55719) LONGITUDE: 97° 25.7' W ( -97.42911)
The bench mark is located approximately 274 m (899 ft) SSW of the Port
Mansfield water tower, 48.40 m (158.8 ft) NE of the centerline of the entrance
to the Port Mansfield Marina, 24.10 m (79.10 ft) ESE of the centerline of Port
Mansfield Road, and 23.90 m (78.4 ft) NNW of a light pole. The bench mark is a
disk crimped to the top of a stainless steel rod and encased in a 4 inch PVC
pipe with concrete kickblock.
BENCH MARK STAMPING: 8490 E 1990
DESIGNATION: 877 8490 E
MONUMENTATION: Tidal Station disk VM#: 3108
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 26° 33.4' N ( 26.55689) LONGITUDE: 97° 25.8' W ( -97.43025)
The bench mark is a disk located 0.5 km (0.3 mi) SW of the the east end of Port
Mansfield Drive, 45.20 m (148.3 ft) NE of a power pole, 32.49 m (106.6 ft) SW of
the SW corner of parking lot, and 0.61 m (2.0 ft) south of a witness post. The
bench mark is set 3 cm (0.1 ft) below the ground, crimped to the top of a
stainless steel rod driven an unspecified depth, and encased in a 5 inch PVC
pipe with concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8490 G 1993
DESIGNATION: 877 8490 G
MONUMENTATION: Tidal Station disk VM#: 12491
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete foundation OPUS PID:
LATITUDE: 26° 33.5' N ( 26.55858) LONGITUDE: 97° 25.7' W ( -97.42828)
The bench mark is a disk set flush in the south end of a concrete foundation for
a water tower, 51.79 m (169.9 ft) NW of the centerline of Port Mansfield Drive,
26.30 m (86.3 ft) WSW of the centerline of a dirt road leading to trailer park,
and 16.70 m (54.8 ft) NNW of the north compass point on a water storage tank
south of water tower.
BENCH MARK STAMPING: 8490 H 2005
DESIGNATION: 877 8490 H
MONUMENTATION: Bench Mark disk VM#: 20548
AGENCY: Conrad Blucher Institute (CBI) IDB PID:
SETTING CLASSIFICATION: Bulkhead OPUS PID:
LATITUDE: 26° 33.5' N ( 26.55783) LONGITUDE: 97° 25.5' W ( -97.42542)
The bench mark is a disk located on seawall bulkhead approximately 38.00 m
(124.7 ft) NNE of the tide gauge station, 14.50 m (47.6 ft) east of the eastern
most boat slip along the harbor channel, and 6.00 m (19.7 ft) SSE of the SE
corner of the large beach house in the SE corner of Mansfield Point subdivision,
.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
T I D A L D A T U M S
Tidal datums at PORT MANSFIELD based on:
LENGTH OF SERIES: 5 YEARS
TIME PERIOD: 10/12-9/13, 3/14-2/15, 5/16-4/17, 6/17-5/18
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8779770 PORT ISABEL, LAGUNA MADRE
Elevations of tidal datums referred to Mean Sea Level (MSL), in METERS:
MEAN SEA LEVEL MSL = 0.000
North American Vertical Datum NAVD88 = -0.087
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MSL
NO 1 1964 1.645
BM NO 2 1964 1.876
LEGION NO 5 1939 1962 4.089
8490 B 1978 1.684
8490 D 1990 3.407
8490 E 1990 2.902
8490 G 1993 3.553
8490 H 2005 1.902
Foot Notes:
Bench mark '8940 G 1993' is based on one differential leveling connection and
does not meet the quality control standards of the NOS. Therefore, caution
should be used when deriving elevations for this mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8778490 PUBLICATION DATE: 10/15/2020
Name: PORT MANSFIELD
TX
NOAA Chart: 11306 Latitude: 26° 33.5' N ( 26.55764)
USGS Quad: PORT MANSFIELD Longitude: 97° 25.5' W ( -97.42572)
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.