U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8779911 PUBLICATION DATE: 05/17/2021
Name: SAN MARTIN LAKE CHANNEL
TX
NOAA Chart: 11302 Latitude: 26° 0.1' N ( 26.00181)
USGS Quad: LAGUNA VISTA, TX Longitude: 97° 17.9' W ( -97.29856)
To reach from the U.S. Post Office at 103 N Manautou St in Port Isabel, TX,
proceed SW on E Queen Isabella Blvd for 0.45 Km (0.28 mi), the road will then
veer slightly right and become State Park Rd 100, continue SW on State Park Rd
100 for 1.63 Km (1.01 mi) to Brownsville Port Isabel Hwy (State Hwy 48), turn
left onto Brownsville Port Isabel Hwy (State Hwy 48) and proceed SW for 11.3 Km
(7.0 mi) to the Jaime J. Zapata Memorial Boat Ramp on the left just before a
bridge that goes over the San Martin Lake Channel, turn left into the parking
lot and proceed south to the small boat launch facility. The bench marks are
located around the parking area and on the southwestern corner of the bridge.
The tide gauge was located under a wooden walkway attached to a piling, about
12.2 m (40 ft) from shore, on the southeasternmost of three walkways.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 9911 A 2019
DESIGNATION: 877 9911 A
MONUMENTATION: Tidal Station disk VM#: 23373
AGENCY: National Ocean Survey/Service (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete Pad OPUS PID:
LATITUDE: 26° 0.1' N ( 26.00189) LONGITUDE: 97° 17.9' W ( -97.29839)
The bench mark is a disk set in a concrete pad used for the boat launch, 57.00 m
(187.0 ft) south of a light pole near the southern side of the entrance to the
boat ramp, 53.12 m (174.3 ft) SSW of the SW corner for a picnic pavilion, 17.80
m (58.4 ft) SE of a light pole near the western corner of the concrete pad, 4.32
m (14.2 ft) north of the SE corner of the concrete pad and 2.30 m (7.5 ft) NNE
of a light pole near the SW edge of the concrete pad.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8779911 PUBLICATION DATE: 05/17/2021
Name: SAN MARTIN LAKE CHANNEL
TX
NOAA Chart: 11302 Latitude: 26° 0.1' N ( 26.00181)
USGS Quad: LAGUNA VISTA, TX Longitude: 97° 17.9' W ( -97.29856)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: PHR 031 0051
DESIGNATION: PHR 031 0051
MONUMENTATION: Metal Rod VM#: 23374
AGENCY: Texas Department of Transportation IDB PID:
SETTING CLASSIFICATION: Stainless steel rod w/o sleeve. OPUS PID#: BBGJ84
LATITUDE: 26° 0.1' N ( 26.00231) LONGITUDE: 97° 17.9' W ( -97.29892)
The bench mark is a flange encased rod set in the grass near the guardrail near
the SE corner of the bridge which crosses the San Martin Lake Channel, 77.5 m
(254.3 ft) west of the NW corner of a pavilion, 35.7 m (117.1 ft) WSW of a light
pole at the edge of a ramp that goes to the boat launch, 13.50 m (44.3 ft) SE of
the centerline of State highway 48, 3.10 m (10.2 ft) ENE of the NE end of the
bridge at the retaining wall, 2.15 m (7.1 ft) NW of a power pole with no wires
attached, 0.40 m (1.3 ft) SE of the guard rail and 0.19 m (0.6 ft) SE of a
carsonite post. The datum point is set 22 cm (9 inches) below the ground, being
the top of a stainless steel rod driven to an unspecified depth and encased in a
lid with concrete kick block.
BENCH MARK STAMPING: 9911 B 2019
DESIGNATION: 877 9911 B
MONUMENTATION: Tidal Station disk VM#: 23375
AGENCY: National Ocean Survey/Service (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete Retaining Wall OPUS PID:
LATITUDE: 26° 0.1' N ( 26.00181) LONGITUDE: 97° 18.0' W ( -97.29983)
The bench mark is a disk set in the top of a 0.20 m (0.7 ft) wide concrete
retaining wall near the SW corner of the bridge which crosses the San Martin
Lake Channel, 13.30 m (43.6 ft) SE of the centerline of State Highway 48, 6.63 m
(21.8 ft) WSW of where the concrete starts at the SW side of the bridge, 2.15 m
(7.1 ft) ENE of the centerline of a 1.22 m (4.0 ft) wide concrete walkway and
1.38 m (4.5 ft) WSW of the most southeasterly fog light.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8779911 PUBLICATION DATE: 05/17/2021
Name: SAN MARTIN LAKE CHANNEL
TX
NOAA Chart: 11302 Latitude: 26° 0.1' N ( 26.00181)
USGS Quad: LAGUNA VISTA, TX Longitude: 97° 17.9' W ( -97.29856)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9911 C 2019
DESIGNATION: 877 9911 C
MONUMENTATION: Flange-encased Rod VM#: 23376
AGENCY: National Ocean Survey/Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: BBGS27
LATITUDE: 26° 0.1' N ( 26.00216) LONGITUDE: 97° 17.9' W ( -97.29785)
The bench mark is a flange encased rod set in the field near the eastern corner
of the parking lot for the Jaime J. Zapata Memorial boat launch, 25.30 m (83.0
ft) east of the NE corer of a picnic pavilion, 20.77 m (68.1 ft) NNE of a corner
in a concrete sidewalk, 16.95 m (55.6 ft) east of a light pole that is near the
eastern side of a picnic pavilion, 13.50 m (44.3 ft) north of a light pole, 2.90
m (9.5 ft) ENE of an 20 cm (8 inches) diameter piling and 0.40 m (1.3 ft) south
of a carsonite post. The datum point is set 5 cm (2 inches) below ground, being
the top of a stainless steel rod driven 12.8 m (42.0 ft) until refusal and
encased in a 7.25-in (18 cm) nos logo cap with concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8779911 PUBLICATION DATE: 05/17/2021
Name: SAN MARTIN LAKE CHANNEL
TX
NOAA Chart: 11302 Latitude: 26° 0.1' N ( 26.00181)
USGS Quad: LAGUNA VISTA, TX Longitude: 97° 17.9' W ( -97.29856)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 9911 D 2019
DESIGNATION: 877 9911 D
MONUMENTATION: Flange-encased Rod VM#: 23377
AGENCY: National Ocean Survey/Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve. OPUS PID:
LATITUDE: 26° 0.2' N ( 26.00258) LONGITUDE: 97° 17.9' W ( -97.29831)
The bench mark is a flange encased rod set in the dirt near the eastern side of
the driveway leading into Jaime J. Zapata Memorial boat launch, 25.65 m (84.2
ft) WNW of the NW corner of a picnic pavilion, 24.03 m (78.8 ft) SSE of the
centerline of State Highway 48, 14.41 m (47.3 ft) north of a light pole, 7.75 m
(25.4 ft) north of a concrete sidewalk, 2.80 m (9.2 ft) SE of a 20 cm (8 inches)
diameter piling at the corner of a cable and pile fence and 0.30 m (1.0 ft)
south of a carsonite post. The datum point is set 3 cm (1 inch) below ground,
being the top of a stainless steel rod driven 12.2 m (40.0 ft) until refusal and
encased in a 7.25-in (18 cm) nos logo cap with concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8779911 PUBLICATION DATE: 05/17/2021
Name: SAN MARTIN LAKE CHANNEL
TX
NOAA Chart: 11302 Latitude: 26° 0.1' N ( 26.00181)
USGS Quad: LAGUNA VISTA, TX Longitude: 97° 17.9' W ( -97.29856)
T I D A L D A T U M S
Tidal datums at SAN MARTIN LAKE CHANNEL based on:
LENGTH OF SERIES: 5 MONTHS
TIME PERIOD: January 2020 - May 2020
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8779770 PORT ISABEL, LAGUNA MADRE
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.415
MEAN HIGH WATER MHW = 0.392
North American Vertical Datum NAVD88 = 0.275
MEAN SEA LEVEL MSL = 0.243
MEAN TIDE LEVEL MTL = 0.224
MEAN LOW WATER MLW = 0.055
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
9911 A 2019 0.972 0.580
PHR 031 0051 3.195 2.803
9911 B 2019 4.318 3.926
9911 C 2019 0.716 0.324
9911 D 2019 1.088 0.696
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8779911 PUBLICATION DATE: 05/17/2021
Name: SAN MARTIN LAKE CHANNEL
TX
NOAA Chart: 11302 Latitude: 26° 0.1' N ( 26.00181)
USGS Quad: LAGUNA VISTA, TX Longitude: 97° 17.9' W ( -97.29856)
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.