U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8770971 PUBLICATION DATE: 12/17/2019
Name: ROLLOVER PASS
TX
NOAA Chart: 11331 Latitude: 29° 30.9' N ( 29.51556)
USGS Quad: FROZEN POINT Longitude: 94° 30.6' W ( -94.51056)
To reach the tidal bench marks from the town of Gilchrist, go about 4.0 km (2.5
mi) to paved road on the right (about 0.8 km (0.5 mi) from Rollover Pass
bridge). Turn onto said paved road which will lead to Dr. Lauderdale Public
Boat Ramp, and travel for about 1.1 km (0.7 mi) to shell surface road on the
right. Follow shell road for about 91.44 m (300.0 ft) to where it makes a hard
tur to the left. Follow to the left for about another 91.44 m (300.0 ft) to the
end of the road on the bay. The tide station is on a structure near a wooden
fishing pier. The staff is also fastened to the same structure.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: LUB 0971 A 1994
DESIGNATION: 877 0971 A
MONUMENTATION: Bench Mark disk VM#: 14095
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: BBGC92
LATITUDE: 29° 30.9' N ( 29.51531) LONGITUDE: 94° 30.7' W ( -94.51103)
The primary bench mark is a brass disk located 33.19 m (108.89 ft) SW of the
edge of the pier, 16.15 m (52.99 ft) NE of the north corner of a house at lot
1765, and 0.55 m (1.80 ft) east of a wood utility pole. The bench mark is
crimped to a stainless steel rod driven 16.8 m (55.1 ft) to refusal, and encased
in a 6-inch PVC pipe with concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8770971 PUBLICATION DATE: 12/17/2019
Name: ROLLOVER PASS
TX
NOAA Chart: 11331 Latitude: 29° 30.9' N ( 29.51556)
USGS Quad: FROZEN POINT Longitude: 94° 30.6' W ( -94.51056)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LUB 0971 C 1994
DESIGNATION: 877 0971 C
MONUMENTATION: Bench Mark disk VM#: 14097
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 30.9' N ( 29.51464) LONGITUDE: 94° 30.6' W ( -94.51069)
The bench mark is a brass disk located 55.17 m (181.00 ft) SE of LUB 0971 B
1994, 40.23 m NE of LUB 0971 D 1994, 11.49 m (37.70 ft) south of the SW most
poling of a house lot 1750, 8.23 m (27.00 ft) ESE of the centerline of gravel
drive, and .52 m (1.71 ft) west of a wood utility pole. The bench mark is
crimped to a stainless steel rod drven 16.8 m (55.1 ft) to refusal, and encased
in a 6 inch PVC pipe with concrete kickblock.
BENCH MARK STAMPING: LUB 0971 D 1994
DESIGNATION: 877 0971 D TIDAL
MONUMENTATION: Bench Mark disk VM#: 14098
AGENCY: National Ocean Service (NOS) IDB PID#: DO9992
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#:
LATITUDE: 29° 30.9' N ( 29.51444) LONGITUDE: 94° 30.7' W ( -94.51103)
The bench mark is a brass disk located 66.14 m (216.99 ft) ENE of the centerline
of Yaught Basin Road, 40.23 m (131.99 ft) SW of LUB 0971 C 1994, 3.57 m (11.71
ft) SSE of the centerline of drive and 1.83 m (6.00 ft) NW of a wood utility
pole. The bench mark is a brass disk crimped to a stainless steel rod driven
16.8 m (55.1 ft) to refusal and encased in a 6 inch PVC pipe with concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8770971 PUBLICATION DATE: 12/17/2019
Name: ROLLOVER PASS
TX
NOAA Chart: 11331 Latitude: 29° 30.9' N ( 29.51556)
USGS Quad: FROZEN POINT Longitude: 94° 30.6' W ( -94.51056)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0971 F 2017
DESIGNATION: 877 0971 F
MONUMENTATION: Metal Rod VM#: 22626
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod with sleeve OPUS PID:
LATITUDE: 29° 30.7' N ( 29.51089) LONGITUDE: 94° 30.6' W ( -94.50992)
The bench mark is a stainless steel rod located 121 m (397 ft) NNW of bench mark
877 0971 G, 59.3 m (194.6 ft) WNW of the eleventh powerpole from State Highway
87, and 10.5 m (34.4 ft) SW of the centerline of Yacht Basin Road. The mark is a
stainless steel rod driven 17.2 m (56.4 ft) to refusal with a 1.2 m (4 ft)
sleeve and encased in a six inch PVC tube with a concrete kickblock.
BENCH MARK STAMPING: 0971 G 2017
DESIGNATION: 877 0971 G
MONUMENTATION: Metal Rod VM#: 22627
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: OPUS PID:
LATITUDE: 29° 30.6' N ( 29.50989) LONGITUDE: 94° 30.6' W ( -94.50942)
The mark is a stainless steel rod located 121 m (397 ft) SSE of bench mark 877
0971 F, 8.2 m (26.9 ft) SW of the centerline of Yacht Basin Road, and 1.4 m (4.6
ft) south of the nineth telephone pole starting from Highway 87. The mark is a
stainless steel rod driven 23 m (75.4 ft) to refusal with a 4 ft sleeve and is
encased in a six inch PVC with a concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8770971 PUBLICATION DATE: 12/17/2019
Name: ROLLOVER PASS
TX
NOAA Chart: 11331 Latitude: 29° 30.9' N ( 29.51556)
USGS Quad: FROZEN POINT Longitude: 94° 30.6' W ( -94.51056)
T I D A L D A T U M S
Tidal datums at ROLLOVER PASS based on:
LENGTH OF SERIES: 2 YEARS
TIME PERIOD: January 2017 - December 2018
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8771013 EAGLE POINT, GALVESTON BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (08/27/2017) = 1.348
MEAN HIGHER HIGH WATER MHHW = 0.412
MEAN HIGH WATER MHW = 0.381
North American Vertical Datum NAVD88 = 0.226
MEAN SEA LEVEL MSL = 0.225
MEAN TIDE LEVEL MTL = 0.219
MEAN LOW WATER MLW = 0.056
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (12/21/2018) = -0.400
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
LUB 0971 A 1994 1.508 1.127
LUB 0971 C 1994 1.953 1.572
LUB 0971 D 1994 2.074 1.693
0971 F 2017 0.653 0.272
0971 G 2017 0.727 0.346
Foot Notes:
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8770971 PUBLICATION DATE: 12/17/2019
Name: ROLLOVER PASS
TX
NOAA Chart: 11331 Latitude: 29° 30.9' N ( 29.51556)
USGS Quad: FROZEN POINT Longitude: 94° 30.6' W ( -94.51056)
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.