U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8772132 PUBLICATION DATE: 11/10/2003
Name: CHRISTMAS BAY
TX
NOAA Chart: 11322 Latitude: 29° 2.5' N ( 29.04170)
USGS Quad: CHRISTMAS POINT Longitude: 95° 10.5' W ( -95.17500)
To reach the tidal bench marks from the Galveston County courthouse on 21st
Street (Moody Avenue), proceed 1.4 km (0.9 mi) south on 21st Street to the
junction of Seawall Boulevard, then turn right onto Seawall Boulevard and
continue 9.3 km (5.8 mi) to the junction of FM Road 3005 (Termini Road).
Continue straight for 48.6 km (30.2 mi) to Kahuna RV Park and Condos sign, then
turn right onto Brazoria County gravel road No. 257Q, and continue it around two
curves for 1.1 km (0.7 mi) to the end of the road on the edge of the water and a
wood pier. The tidal bench marks are located along the road. The staff was
fastened to a square piling on the channel side of the pier. The tide station
was located on the same pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 90025 A 1990
DESIGNATION: 877 2132 A
MONUMENTATION: Tidal Station disk VM#: 12360
AGENCY: Conrad Blucher Institute (CBI) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 2.1' N ( 29.03500) LONGITUDE: 95° 11.7' W ( -95.19500)
The primary bench mark is a disk located at the west end of County Road No.
257Q, 6.86 m (22.5 ft) east from the west corner of the concrete slab of
two-story condominiums on stilts, and 0.6 m (2.0 ft) from the NW corner of the
northerly condo unit. The bench mark is crimped to the top of a stainless steel
rod driven 9.1 m (30 ft) to refusal, and encased in a 6-inch PVC pipe and
concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8772132 PUBLICATION DATE: 11/10/2003
Name: CHRISTMAS BAY
TX
NOAA Chart: 11322 Latitude: 29° 2.5' N ( 29.04170)
USGS Quad: CHRISTMAS POINT Longitude: 95° 10.5' W ( -95.17500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 90025 B 1990
DESIGNATION: 877 2132 B
MONUMENTATION: Tidal Station disk VM#: 12361
AGENCY: Conrad Blucher Institute (CBI) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 2.1' N ( 29.03500) LONGITUDE: 95° 11.7' W ( -95.19500)
The bench mark is a disk located on the south side of the county road, 91 m (300
ft) SE from bench mark 90025 A 19905, and 5.18 m (17.0 ft) from the centerline
of the country road. The bench mark is crimped to the top of a stainless steel
rod driven 9.1 m (30 ft) to refusal, and encased in a 6-inch PVC pipe and
concrete kickblock.
BENCH MARK STAMPING: 90025 C 1990
DESIGNATION: 877 2132 C
MONUMENTATION: Tidal Station disk VM#: 12362
AGENCY: Conrad Blucher Institute (CBI) IDB PID#: AW7126
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 2.1' N ( 29.03500) LONGITUDE: 95° 11.7' W ( -95.19500)
The bench mark is a disk located on the south side of the county road, 76 m (250
ft) SE from bench mark 90025 B 1990, and 4 m (14 ft) from the centerline of the
country road. The bench mark is crimped to the top of a stainless steel rod
driven 9.1 m (30 ft) to refusal, and encased in a 6-inch PVC pipe and concrete
kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8772132 PUBLICATION DATE: 11/10/2003
Name: CHRISTMAS BAY
TX
NOAA Chart: 11322 Latitude: 29° 2.5' N ( 29.04170)
USGS Quad: CHRISTMAS POINT Longitude: 95° 10.5' W ( -95.17500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 90025 D 1990
DESIGNATION: 877 2132 D
MONUMENTATION: Tidal Station disk VM#: 12363
AGENCY: Conrad Blucher Institute (CBI) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 2.1' N ( 29.03500) LONGITUDE: 95° 11.7' W ( -95.19500)
The bench mark is a disk located on the south side of the county road, 91 m (300
ft) SE from bench mark 90025 C 1990, 5.03 m (16.5 ft) from a power pole, and 4 m
(14 ft) from the centerline of the country road. The bench mark is crimped to
the top of a stainless steel rod driven 12.2 m (40.0 ft) to refusal, and encased
in a 6-inch PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 90025 E 1990
DESIGNATION: 877 2132 E
MONUMENTATION: Tidal Station disk VM#: 12364
AGENCY: Conrad Blucher Institute (CBI) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 29° 2.1' N ( 29.03500) LONGITUDE: 95° 11.7' W ( -95.19500)
The bench mark is a disk located on the south side of the county road, 91 m (300
ft) SE from bench mark 90025 D 1990, 5 m (15.0 ft) from a power pole, and 4 m
(13 ft) from the centerline of the country road. The bench mark is crimped to
the top of a stainless steel rod driven 9.1 m (30.0 ft) to refusal, and encased
in a 6-inch PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8772132 PUBLICATION DATE: 11/10/2003
Name: CHRISTMAS BAY
TX
NOAA Chart: 11322 Latitude: 29° 2.5' N ( 29.04170)
USGS Quad: CHRISTMAS POINT Longitude: 95° 10.5' W ( -95.17500)
T I D A L D A T U M S
Tidal datums at CHRISTMAS BAY based on:
LENGTH OF SERIES: 3 YEARS
TIME PERIOD: August 1992 - July 1995
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8772440 FREEPORT, DOW BARGE CANAL
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
HIGHEST OBSERVED WATER LEVEL (06/19/1993) = 0.992
MEAN HIGHER HIGH WATER MHHW = 0.249
MEAN HIGH WATER MHW = 0.236
MEAN SEA LEVEL MSL = 0.134
MEAN TIDE LEVEL MTL = 0.128
MEAN LOW WATER MLW = 0.020
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (03/14/1993) = -0.526
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
90025 A 1990 0.832 0.596
90025 B 1990 0.695 0.459
90025 C 1990 0.766 0.530
90025 D 1990 0.759 0.523
90025 E 1990 0.791 0.555
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8772132 PUBLICATION DATE: 11/10/2003
Name: CHRISTMAS BAY
TX
NOAA Chart: 11322 Latitude: 29° 2.5' N ( 29.04170)
USGS Quad: CHRISTMAS POINT Longitude: 95° 10.5' W ( -95.17500)
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.